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+=======================
+A Linux CD-ROM standard
+=======================
+
+:Author: David van Leeuwen <david@ElseWare.cistron.nl>
+:Date: 12 March 1999
+:Updated by: Erik Andersen (andersee@debian.org)
+:Updated by: Jens Axboe (axboe@image.dk)
+
+
+Introduction
+============
+
+Linux is probably the Unix-like operating system that supports
+the widest variety of hardware devices. The reasons for this are
+presumably
+
+- The large list of hardware devices available for the many platforms
+  that Linux now supports (i.e., i386-PCs, Sparc Suns, etc.)
+- The open design of the operating system, such that anybody can write a
+  driver for Linux.
+- There is plenty of source code around as examples of how to write a driver.
+
+The openness of Linux, and the many different types of available
+hardware has allowed Linux to support many different hardware devices.
+Unfortunately, the very openness that has allowed Linux to support
+all these different devices has also allowed the behavior of each
+device driver to differ significantly from one device to another.
+This divergence of behavior has been very significant for CD-ROM
+devices; the way a particular drive reacts to a `standard` *ioctl()*
+call varies greatly from one device driver to another. To avoid making
+their drivers totally inconsistent, the writers of Linux CD-ROM
+drivers generally created new device drivers by understanding, copying,
+and then changing an existing one. Unfortunately, this practice did not
+maintain uniform behavior across all the Linux CD-ROM drivers.
+
+This document describes an effort to establish Uniform behavior across
+all the different CD-ROM device drivers for Linux. This document also
+defines the various *ioctl()'s*, and how the low-level CD-ROM device
+drivers should implement them. Currently (as of the Linux 2.1.\ *x*
+development kernels) several low-level CD-ROM device drivers, including
+both IDE/ATAPI and SCSI, now use this Uniform interface.
+
+When the CD-ROM was developed, the interface between the CD-ROM drive
+and the computer was not specified in the standards. As a result, many
+different CD-ROM interfaces were developed. Some of them had their
+own proprietary design (Sony, Mitsumi, Panasonic, Philips), other
+manufacturers adopted an existing electrical interface and changed
+the functionality (CreativeLabs/SoundBlaster, Teac, Funai) or simply
+adapted their drives to one or more of the already existing electrical
+interfaces (Aztech, Sanyo, Funai, Vertos, Longshine, Optics Storage and
+most of the `NoName` manufacturers). In cases where a new drive really
+brought its own interface or used its own command set and flow control
+scheme, either a separate driver had to be written, or an existing
+driver had to be enhanced. History has delivered us CD-ROM support for
+many of these different interfaces. Nowadays, almost all new CD-ROM
+drives are either IDE/ATAPI or SCSI, and it is very unlikely that any
+manufacturer will create a new interface. Even finding drives for the
+old proprietary interfaces is getting difficult.
+
+When (in the 1.3.70's) I looked at the existing software interface,
+which was expressed through `cdrom.h`, it appeared to be a rather wild
+set of commands and data formats [#f1]_. It seemed that many
+features of the software interface had been added to accommodate the
+capabilities of a particular drive, in an *ad hoc* manner. More
+importantly, it appeared that the behavior of the `standard` commands
+was different for most of the different drivers: e. g., some drivers
+close the tray if an *open()* call occurs when the tray is open, while
+others do not. Some drivers lock the door upon opening the device, to
+prevent an incoherent file system, but others don't, to allow software
+ejection. Undoubtedly, the capabilities of the different drives vary,
+but even when two drives have the same capability their drivers'
+behavior was usually different.
+
+.. [#f1]
+   I cannot recollect what kernel version I looked at, then,
+   presumably 1.2.13 and 1.3.34 --- the latest kernel that I was
+   indirectly involved in.
+
+I decided to start a discussion on how to make all the Linux CD-ROM
+drivers behave more uniformly. I began by contacting the developers of
+the many CD-ROM drivers found in the Linux kernel. Their reactions
+encouraged me to write the Uniform CD-ROM Driver which this document is
+intended to describe. The implementation of the Uniform CD-ROM Driver is
+in the file `cdrom.c`. This driver is intended to be an additional software
+layer that sits on top of the low-level device drivers for each CD-ROM drive.
+By adding this additional layer, it is possible to have all the different
+CD-ROM devices behave **exactly** the same (insofar as the underlying
+hardware will allow).
+
+The goal of the Uniform CD-ROM Driver is **not** to alienate driver developers
+whohave not yet taken steps to support this effort. The goal of Uniform CD-ROM
+Driver is simply to give people writing application programs for CD-ROM drives
+**one** Linux CD-ROM interface with consistent behavior for all
+CD-ROM devices. In addition, this also provides a consistent interface
+between the low-level device driver code and the Linux kernel. Care
+is taken that 100% compatibility exists with the data structures and
+programmer's interface defined in `cdrom.h`. This guide was written to
+help CD-ROM driver developers adapt their code to use the Uniform CD-ROM
+Driver code defined in `cdrom.c`.
+
+Personally, I think that the most important hardware interfaces are
+the IDE/ATAPI drives and, of course, the SCSI drives, but as prices
+of hardware drop continuously, it is also likely that people may have
+more than one CD-ROM drive, possibly of mixed types. It is important
+that these drives behave in the same way. In December 1994, one of the
+cheapest CD-ROM drives was a Philips cm206, a double-speed proprietary
+drive. In the months that I was busy writing a Linux driver for it,
+proprietary drives became obsolete and IDE/ATAPI drives became the
+standard. At the time of the last update to this document (November
+1997) it is becoming difficult to even **find** anything less than a
+16 speed CD-ROM drive, and 24 speed drives are common.
+
+.. _cdrom_api:
+
+Standardizing through another software level
+============================================
+
+At the time this document was conceived, all drivers directly
+implemented the CD-ROM *ioctl()* calls through their own routines. This
+led to the danger of different drivers forgetting to do important things
+like checking that the user was giving the driver valid data. More
+importantly, this led to the divergence of behavior, which has already
+been discussed.
+
+For this reason, the Uniform CD-ROM Driver was created to enforce consistent
+CD-ROM drive behavior, and to provide a common set of services to the various
+low-level CD-ROM device drivers. The Uniform CD-ROM Driver now provides another
+software-level, that separates the *ioctl()* and *open()* implementation
+from the actual hardware implementation. Note that this effort has
+made few changes which will affect a user's application programs. The
+greatest change involved moving the contents of the various low-level
+CD-ROM drivers\' header files to the kernel's cdrom directory. This was
+done to help ensure that the user is only presented with only one cdrom
+interface, the interface defined in `cdrom.h`.
+
+CD-ROM drives are specific enough (i. e., different from other
+block-devices such as floppy or hard disc drives), to define a set
+of common **CD-ROM device operations**, *<cdrom-device>_dops*.
+These operations are different from the classical block-device file
+operations, *<block-device>_fops*.
+
+The routines for the Uniform CD-ROM Driver interface level are implemented
+in the file `cdrom.c`. In this file, the Uniform CD-ROM Driver interfaces
+with the kernel as a block device by registering the following general
+*struct file_operations*::
+
+	struct file_operations cdrom_fops = {
+		NULL,			/∗ lseek ∗/
+		block _read ,		/∗ read—general block-dev read ∗/
+		block _write,		/∗ write—general block-dev write ∗/
+		NULL,			/∗ readdir ∗/
+		NULL,			/∗ select ∗/
+		cdrom_ioctl,		/∗ ioctl ∗/
+		NULL,			/∗ mmap ∗/
+		cdrom_open,		/∗ open ∗/
+		cdrom_release,		/∗ release ∗/
+		NULL,			/∗ fsync ∗/
+		NULL,			/∗ fasync ∗/
+		NULL			/∗ revalidate ∗/
+	};
+
+Every active CD-ROM device shares this *struct*. The routines
+declared above are all implemented in `cdrom.c`, since this file is the
+place where the behavior of all CD-ROM-devices is defined and
+standardized. The actual interface to the various types of CD-ROM
+hardware is still performed by various low-level CD-ROM-device
+drivers. These routines simply implement certain **capabilities**
+that are common to all CD-ROM (and really, all removable-media
+devices).
+
+Registration of a low-level CD-ROM device driver is now done through
+the general routines in `cdrom.c`, not through the Virtual File System
+(VFS) any more. The interface implemented in `cdrom.c` is carried out
+through two general structures that contain information about the
+capabilities of the driver, and the specific drives on which the
+driver operates. The structures are:
+
+cdrom_device_ops
+  This structure contains information about the low-level driver for a
+  CD-ROM device. This structure is conceptually connected to the major
+  number of the device (although some drivers may have different
+  major numbers, as is the case for the IDE driver).
+
+cdrom_device_info
+  This structure contains information about a particular CD-ROM drive,
+  such as its device name, speed, etc. This structure is conceptually
+  connected to the minor number of the device.
+
+Registering a particular CD-ROM drive with the Uniform CD-ROM Driver
+is done by the low-level device driver though a call to::
+
+	register_cdrom(struct cdrom_device_info * <device>_info)
+
+The device information structure, *<device>_info*, contains all the
+information needed for the kernel to interface with the low-level
+CD-ROM device driver. One of the most important entries in this
+structure is a pointer to the *cdrom_device_ops* structure of the
+low-level driver.
+
+The device operations structure, *cdrom_device_ops*, contains a list
+of pointers to the functions which are implemented in the low-level
+device driver. When `cdrom.c` accesses a CD-ROM device, it does it
+through the functions in this structure. It is impossible to know all
+the capabilities of future CD-ROM drives, so it is expected that this
+list may need to be expanded from time to time as new technologies are
+developed. For example, CD-R and CD-R/W drives are beginning to become
+popular, and support will soon need to be added for them. For now, the
+current *struct* is::
+
+	struct cdrom_device_ops {
+		int (*open)(struct cdrom_device_info *, int)
+		void (*release)(struct cdrom_device_info *);
+		int (*drive_status)(struct cdrom_device_info *, int);
+		unsigned int (*check_events)(struct cdrom_device_info *,
+					     unsigned int, int);
+		int (*media_changed)(struct cdrom_device_info *, int);
+		int (*tray_move)(struct cdrom_device_info *, int);
+		int (*lock_door)(struct cdrom_device_info *, int);
+		int (*select_speed)(struct cdrom_device_info *, int);
+		int (*select_disc)(struct cdrom_device_info *, int);
+		int (*get_last_session) (struct cdrom_device_info *,
+					 struct cdrom_multisession *);
+		int (*get_mcn)(struct cdrom_device_info *, struct cdrom_mcn *);
+		int (*reset)(struct cdrom_device_info *);
+		int (*audio_ioctl)(struct cdrom_device_info *,
+				   unsigned int, void *);
+		const int capability;		/* capability flags */
+		int (*generic_packet)(struct cdrom_device_info *,
+				      struct packet_command *);
+	};
+
+When a low-level device driver implements one of these capabilities,
+it should add a function pointer to this *struct*. When a particular
+function is not implemented, however, this *struct* should contain a
+NULL instead. The *capability* flags specify the capabilities of the
+CD-ROM hardware and/or low-level CD-ROM driver when a CD-ROM drive
+is registered with the Uniform CD-ROM Driver.
+
+Note that most functions have fewer parameters than their
+*blkdev_fops* counterparts. This is because very little of the
+information in the structures *inode* and *file* is used. For most
+drivers, the main parameter is the *struct* *cdrom_device_info*, from
+which the major and minor number can be extracted. (Most low-level
+CD-ROM drivers don't even look at the major and minor number though,
+since many of them only support one device.) This will be available
+through *dev* in *cdrom_device_info* described below.
+
+The drive-specific, minor-like information that is registered with
+`cdrom.c`, currently contains the following fields::
+
+  struct cdrom_device_info {
+	const struct cdrom_device_ops * ops; 	/* device operations for this major */
+	struct list_head list;			/* linked list of all device_info */
+	struct gendisk * disk;			/* matching block layer disk */
+	void *  handle;				/* driver-dependent data */
+
+	int mask; 				/* mask of capability: disables them */
+	int speed;				/* maximum speed for reading data */
+	int capacity;				/* number of discs in a jukebox */
+
+	unsigned int options:30;		/* options flags */
+	unsigned mc_flags:2;			/*  media-change buffer flags */
+	unsigned int vfs_events;		/*  cached events for vfs path */
+	unsigned int ioctl_events;		/*  cached events for ioctl path */
+	int use_count;				/*  number of times device is opened */
+	char name[20];				/*  name of the device type */
+
+	__u8 sanyo_slot : 2;			/*  Sanyo 3-CD changer support */
+	__u8 keeplocked : 1;			/*  CDROM_LOCKDOOR status */
+	__u8 reserved : 5;			/*  not used yet */
+	int cdda_method;			/*  see CDDA_* flags */
+	__u8 last_sense;			/*  saves last sense key */
+	__u8 media_written;			/*  dirty flag, DVD+RW bookkeeping */
+	unsigned short mmc3_profile;		/*  current MMC3 profile */
+	int for_data;				/*  unknown:TBD */
+	int (*exit)(struct cdrom_device_info *);/*  unknown:TBD */
+	int mrw_mode_page;			/*  which MRW mode page is in use */
+  };
+
+Using this *struct*, a linked list of the registered minor devices is
+built, using the *next* field. The device number, the device operations
+struct and specifications of properties of the drive are stored in this
+structure.
+
+The *mask* flags can be used to mask out some of the capabilities listed
+in *ops->capability*, if a specific drive doesn't support a feature
+of the driver. The value *speed* specifies the maximum head-rate of the
+drive, measured in units of normal audio speed (176kB/sec raw data or
+150kB/sec file system data). The parameters are declared *const*
+because they describe properties of the drive, which don't change after
+registration.
+
+A few registers contain variables local to the CD-ROM drive. The
+flags *options* are used to specify how the general CD-ROM routines
+should behave. These various flags registers should provide enough
+flexibility to adapt to the different users' wishes (and **not** the
+`arbitrary` wishes of the author of the low-level device driver, as is
+the case in the old scheme). The register *mc_flags* is used to buffer
+the information from *media_changed()* to two separate queues. Other
+data that is specific to a minor drive, can be accessed through *handle*,
+which can point to a data structure specific to the low-level driver.
+The fields *use_count*, *next*, *options* and *mc_flags* need not be
+initialized.
+
+The intermediate software layer that `cdrom.c` forms will perform some
+additional bookkeeping. The use count of the device (the number of
+processes that have the device opened) is registered in *use_count*. The
+function *cdrom_ioctl()* will verify the appropriate user-memory regions
+for read and write, and in case a location on the CD is transferred,
+it will `sanitize` the format by making requests to the low-level
+drivers in a standard format, and translating all formats between the
+user-software and low level drivers. This relieves much of the drivers'
+memory checking and format checking and translation. Also, the necessary
+structures will be declared on the program stack.
+
+The implementation of the functions should be as defined in the
+following sections. Two functions **must** be implemented, namely
+*open()* and *release()*. Other functions may be omitted, their
+corresponding capability flags will be cleared upon registration.
+Generally, a function returns zero on success and negative on error. A
+function call should return only after the command has completed, but of
+course waiting for the device should not use processor time.
+
+::
+
+	int open(struct cdrom_device_info *cdi, int purpose)
+
+*Open()* should try to open the device for a specific *purpose*, which
+can be either:
+
+- Open for reading data, as done by `mount()` (2), or the
+  user commands `dd` or `cat`.
+- Open for *ioctl* commands, as done by audio-CD playing programs.
+
+Notice that any strategic code (closing tray upon *open()*, etc.) is
+done by the calling routine in `cdrom.c`, so the low-level routine
+should only be concerned with proper initialization, such as spinning
+up the disc, etc.
+
+::
+
+	void release(struct cdrom_device_info *cdi)
+
+Device-specific actions should be taken such as spinning down the device.
+However, strategic actions such as ejection of the tray, or unlocking
+the door, should be left over to the general routine *cdrom_release()*.
+This is the only function returning type *void*.
+
+.. _cdrom_drive_status:
+
+::
+
+	int drive_status(struct cdrom_device_info *cdi, int slot_nr)
+
+The function *drive_status*, if implemented, should provide
+information on the status of the drive (not the status of the disc,
+which may or may not be in the drive). If the drive is not a changer,
+*slot_nr* should be ignored. In `cdrom.h` the possibilities are listed::
+
+
+	CDS_NO_INFO		/* no information available */
+	CDS_NO_DISC		/* no disc is inserted, tray is closed */
+	CDS_TRAY_OPEN		/* tray is opened */
+	CDS_DRIVE_NOT_READY	/* something is wrong, tray is moving? */
+	CDS_DISC_OK		/* a disc is loaded and everything is fine */
+
+::
+
+	int tray_move(struct cdrom_device_info *cdi, int position)
+
+This function, if implemented, should control the tray movement. (No
+other function should control this.) The parameter *position* controls
+the desired direction of movement:
+
+- 0 Close tray
+- 1 Open tray
+
+This function returns 0 upon success, and a non-zero value upon
+error. Note that if the tray is already in the desired position, no
+action need be taken, and the return value should be 0.
+
+::
+
+	int lock_door(struct cdrom_device_info *cdi, int lock)
+
+This function (and no other code) controls locking of the door, if the
+drive allows this. The value of *lock* controls the desired locking
+state:
+
+- 0 Unlock door, manual opening is allowed
+- 1 Lock door, tray cannot be ejected manually
+
+This function returns 0 upon success, and a non-zero value upon
+error. Note that if the door is already in the requested state, no
+action need be taken, and the return value should be 0.
+
+::
+
+	int select_speed(struct cdrom_device_info *cdi, int speed)
+
+Some CD-ROM drives are capable of changing their head-speed. There
+are several reasons for changing the speed of a CD-ROM drive. Badly
+pressed CD-ROM s may benefit from less-than-maximum head rate. Modern
+CD-ROM drives can obtain very high head rates (up to *24x* is
+common). It has been reported that these drives can make reading
+errors at these high speeds, reducing the speed can prevent data loss
+in these circumstances. Finally, some of these drives can
+make an annoyingly loud noise, which a lower speed may reduce.
+
+This function specifies the speed at which data is read or audio is
+played back. The value of *speed* specifies the head-speed of the
+drive, measured in units of standard cdrom speed (176kB/sec raw data
+or 150kB/sec file system data). So to request that a CD-ROM drive
+operate at 300kB/sec you would call the CDROM_SELECT_SPEED *ioctl*
+with *speed=2*. The special value `0` means `auto-selection`, i. e.,
+maximum data-rate or real-time audio rate. If the drive doesn't have
+this `auto-selection` capability, the decision should be made on the
+current disc loaded and the return value should be positive. A negative
+return value indicates an error.
+
+::
+
+	int select_disc(struct cdrom_device_info *cdi, int number)
+
+If the drive can store multiple discs (a juke-box) this function
+will perform disc selection. It should return the number of the
+selected disc on success, a negative value on error. Currently, only
+the ide-cd driver supports this functionality.
+
+::
+
+	int get_last_session(struct cdrom_device_info *cdi,
+			     struct cdrom_multisession *ms_info)
+
+This function should implement the old corresponding *ioctl()*. For
+device *cdi->dev*, the start of the last session of the current disc
+should be returned in the pointer argument *ms_info*. Note that
+routines in `cdrom.c` have sanitized this argument: its requested
+format will **always** be of the type *CDROM_LBA* (linear block
+addressing mode), whatever the calling software requested. But
+sanitization goes even further: the low-level implementation may
+return the requested information in *CDROM_MSF* format if it wishes so
+(setting the *ms_info->addr_format* field appropriately, of
+course) and the routines in `cdrom.c` will make the transformation if
+necessary. The return value is 0 upon success.
+
+::
+
+	int get_mcn(struct cdrom_device_info *cdi,
+		    struct cdrom_mcn *mcn)
+
+Some discs carry a `Media Catalog Number` (MCN), also called
+`Universal Product Code` (UPC). This number should reflect the number
+that is generally found in the bar-code on the product. Unfortunately,
+the few discs that carry such a number on the disc don't even use the
+same format. The return argument to this function is a pointer to a
+pre-declared memory region of type *struct cdrom_mcn*. The MCN is
+expected as a 13-character string, terminated by a null-character.
+
+::
+
+	int reset(struct cdrom_device_info *cdi)
+
+This call should perform a hard-reset on the drive (although in
+circumstances that a hard-reset is necessary, a drive may very well not
+listen to commands anymore). Preferably, control is returned to the
+caller only after the drive has finished resetting. If the drive is no
+longer listening, it may be wise for the underlying low-level cdrom
+driver to time out.
+
+::
+
+	int audio_ioctl(struct cdrom_device_info *cdi,
+			unsigned int cmd, void *arg)
+
+Some of the CD-ROM-\ *ioctl()*\ 's defined in `cdrom.h` can be
+implemented by the routines described above, and hence the function
+*cdrom_ioctl* will use those. However, most *ioctl()*\ 's deal with
+audio-control. We have decided to leave these to be accessed through a
+single function, repeating the arguments *cmd* and *arg*. Note that
+the latter is of type *void*, rather than *unsigned long int*.
+The routine *cdrom_ioctl()* does do some useful things,
+though. It sanitizes the address format type to *CDROM_MSF* (Minutes,
+Seconds, Frames) for all audio calls. It also verifies the memory
+location of *arg*, and reserves stack-memory for the argument. This
+makes implementation of the *audio_ioctl()* much simpler than in the
+old driver scheme. For example, you may look up the function
+*cm206_audio_ioctl()* `cm206.c` that should be updated with
+this documentation.
+
+An unimplemented ioctl should return *-ENOSYS*, but a harmless request
+(e. g., *CDROMSTART*) may be ignored by returning 0 (success). Other
+errors should be according to the standards, whatever they are. When
+an error is returned by the low-level driver, the Uniform CD-ROM Driver
+tries whenever possible to return the error code to the calling program.
+(We may decide to sanitize the return value in *cdrom_ioctl()* though, in
+order to guarantee a uniform interface to the audio-player software.)
+
+::
+
+	int dev_ioctl(struct cdrom_device_info *cdi,
+		      unsigned int cmd, unsigned long arg)
+
+Some *ioctl()'s* seem to be specific to certain CD-ROM drives. That is,
+they are introduced to service some capabilities of certain drives. In
+fact, there are 6 different *ioctl()'s* for reading data, either in some
+particular kind of format, or audio data. Not many drives support
+reading audio tracks as data, I believe this is because of protection
+of copyrights of artists. Moreover, I think that if audio-tracks are
+supported, it should be done through the VFS and not via *ioctl()'s*. A
+problem here could be the fact that audio-frames are 2352 bytes long,
+so either the audio-file-system should ask for 75264 bytes at once
+(the least common multiple of 512 and 2352), or the drivers should
+bend their backs to cope with this incoherence (to which I would be
+opposed). Furthermore, it is very difficult for the hardware to find
+the exact frame boundaries, since there are no synchronization headers
+in audio frames. Once these issues are resolved, this code should be
+standardized in `cdrom.c`.
+
+Because there are so many *ioctl()'s* that seem to be introduced to
+satisfy certain drivers [#f2]_, any non-standard *ioctl()*\ s
+are routed through the call *dev_ioctl()*. In principle, `private`
+*ioctl()*\ 's should be numbered after the device's major number, and not
+the general CD-ROM *ioctl* number, `0x53`. Currently the
+non-supported *ioctl()'s* are:
+
+	CDROMREADMODE1, CDROMREADMODE2, CDROMREADAUDIO, CDROMREADRAW,
+	CDROMREADCOOKED, CDROMSEEK, CDROMPLAY-BLK and CDROM-READALL
+
+.. [#f2]
+
+   Is there software around that actually uses these? I'd be interested!
+
+.. _cdrom_capabilities:
+
+CD-ROM capabilities
+-------------------
+
+Instead of just implementing some *ioctl* calls, the interface in
+`cdrom.c` supplies the possibility to indicate the **capabilities**
+of a CD-ROM drive. This can be done by ORing any number of
+capability-constants that are defined in `cdrom.h` at the registration
+phase. Currently, the capabilities are any of::
+
+	CDC_CLOSE_TRAY		/* can close tray by software control */
+	CDC_OPEN_TRAY		/* can open tray */
+	CDC_LOCK		/* can lock and unlock the door */
+	CDC_SELECT_SPEED	/* can select speed, in units of * sim*150 ,kB/s */
+	CDC_SELECT_DISC		/* drive is juke-box */
+	CDC_MULTI_SESSION	/* can read sessions *> rm1* */
+	CDC_MCN			/* can read Media Catalog Number */
+	CDC_MEDIA_CHANGED	/* can report if disc has changed */
+	CDC_PLAY_AUDIO		/* can perform audio-functions (play, pause, etc) */
+	CDC_RESET		/* hard reset device */
+	CDC_IOCTLS		/* driver has non-standard ioctls */
+	CDC_DRIVE_STATUS	/* driver implements drive status */
+
+The capability flag is declared *const*, to prevent drivers from
+accidentally tampering with the contents. The capability flags actually
+inform `cdrom.c` of what the driver can do. If the drive found
+by the driver does not have the capability, is can be masked out by
+the *cdrom_device_info* variable *mask*. For instance, the SCSI CD-ROM
+driver has implemented the code for loading and ejecting CD-ROM's, and
+hence its corresponding flags in *capability* will be set. But a SCSI
+CD-ROM drive might be a caddy system, which can't load the tray, and
+hence for this drive the *cdrom_device_info* struct will have set
+the *CDC_CLOSE_TRAY* bit in *mask*.
+
+In the file `cdrom.c` you will encounter many constructions of the type::
+
+	if (cdo->capability & ∼cdi->mask & CDC _⟨capability⟩) ...
+
+There is no *ioctl* to set the mask... The reason is that
+I think it is better to control the **behavior** rather than the
+**capabilities**.
+
+Options
+-------
+
+A final flag register controls the **behavior** of the CD-ROM
+drives, in order to satisfy different users' wishes, hopefully
+independently of the ideas of the respective author who happened to
+have made the drive's support available to the Linux community. The
+current behavior options are::
+
+	CDO_AUTO_CLOSE	/* try to close tray upon device open() */
+	CDO_AUTO_EJECT	/* try to open tray on last device close() */
+	CDO_USE_FFLAGS	/* use file_pointer->f_flags to indicate purpose for open() */
+	CDO_LOCK	/* try to lock door if device is opened */
+	CDO_CHECK_TYPE	/* ensure disc type is data if opened for data */
+
+The initial value of this register is
+`CDO_AUTO_CLOSE | CDO_USE_FFLAGS | CDO_LOCK`, reflecting my own view on user
+interface and software standards. Before you protest, there are two
+new *ioctl()'s* implemented in `cdrom.c`, that allow you to control the
+behavior by software. These are::
+
+	CDROM_SET_OPTIONS	/* set options specified in (int)arg */
+	CDROM_CLEAR_OPTIONS	/* clear options specified in (int)arg */
+
+One option needs some more explanation: *CDO_USE_FFLAGS*. In the next
+newsection we explain what the need for this option is.
+
+A software package `setcd`, available from the Debian distribution
+and `sunsite.unc.edu`, allows user level control of these flags.
+
+
+The need to know the purpose of opening the CD-ROM device
+=========================================================
+
+Traditionally, Unix devices can be used in two different `modes`,
+either by reading/writing to the device file, or by issuing
+controlling commands to the device, by the device's *ioctl()*
+call. The problem with CD-ROM drives, is that they can be used for
+two entirely different purposes. One is to mount removable
+file systems, CD-ROM's, the other is to play audio CD's. Audio commands
+are implemented entirely through *ioctl()\'s*, presumably because the
+first implementation (SUN?) has been such. In principle there is
+nothing wrong with this, but a good control of the `CD player` demands
+that the device can **always** be opened in order to give the
+*ioctl* commands, regardless of the state the drive is in.
+
+On the other hand, when used as a removable-media disc drive (what the
+original purpose of CD-ROM s is) we would like to make sure that the
+disc drive is ready for operation upon opening the device. In the old
+scheme, some CD-ROM drivers don't do any integrity checking, resulting
+in a number of i/o errors reported by the VFS to the kernel when an
+attempt for mounting a CD-ROM on an empty drive occurs. This is not a
+particularly elegant way to find out that there is no CD-ROM inserted;
+it more-or-less looks like the old IBM-PC trying to read an empty floppy
+drive for a couple of seconds, after which the system complains it
+can't read from it. Nowadays we can **sense** the existence of a
+removable medium in a drive, and we believe we should exploit that
+fact. An integrity check on opening of the device, that verifies the
+availability of a CD-ROM and its correct type (data), would be
+desirable.
+
+These two ways of using a CD-ROM drive, principally for data and
+secondarily for playing audio discs, have different demands for the
+behavior of the *open()* call. Audio use simply wants to open the
+device in order to get a file handle which is needed for issuing
+*ioctl* commands, while data use wants to open for correct and
+reliable data transfer. The only way user programs can indicate what
+their *purpose* of opening the device is, is through the *flags*
+parameter (see `open(2)`). For CD-ROM devices, these flags aren't
+implemented (some drivers implement checking for write-related flags,
+but this is not strictly necessary if the device file has correct
+permission flags). Most option flags simply don't make sense to
+CD-ROM devices: *O_CREAT*, *O_NOCTTY*, *O_TRUNC*, *O_APPEND*, and
+*O_SYNC* have no meaning to a CD-ROM.
+
+We therefore propose to use the flag *O_NONBLOCK* to indicate
+that the device is opened just for issuing *ioctl*
+commands. Strictly, the meaning of *O_NONBLOCK* is that opening and
+subsequent calls to the device don't cause the calling process to
+wait. We could interpret this as don't wait until someone has
+inserted some valid data-CD-ROM. Thus, our proposal of the
+implementation for the *open()* call for CD-ROM s is:
+
+- If no other flags are set than *O_RDONLY*, the device is opened
+  for data transfer, and the return value will be 0 only upon successful
+  initialization of the transfer. The call may even induce some actions
+  on the CD-ROM, such as closing the tray.
+- If the option flag *O_NONBLOCK* is set, opening will always be
+  successful, unless the whole device doesn't exist. The drive will take
+  no actions whatsoever.
+
+And what about standards?
+-------------------------
+
+You might hesitate to accept this proposal as it comes from the
+Linux community, and not from some standardizing institute. What
+about SUN, SGI, HP and all those other Unix and hardware vendors?
+Well, these companies are in the lucky position that they generally
+control both the hardware and software of their supported products,
+and are large enough to set their own standard. They do not have to
+deal with a dozen or more different, competing hardware
+configurations\ [#f3]_.
+
+.. [#f3]
+
+   Incidentally, I think that SUN's approach to mounting CD-ROM s is very
+   good in origin: under Solaris a volume-daemon automatically mounts a
+   newly inserted CD-ROM under `/cdrom/*<volume-name>*`.
+
+   In my opinion they should have pushed this
+   further and have **every** CD-ROM on the local area network be
+   mounted at the similar location, i. e., no matter in which particular
+   machine you insert a CD-ROM, it will always appear at the same
+   position in the directory tree, on every system. When I wanted to
+   implement such a user-program for Linux, I came across the
+   differences in behavior of the various drivers, and the need for an
+   *ioctl* informing about media changes.
+
+We believe that using *O_NONBLOCK* to indicate that a device is being opened
+for *ioctl* commands only can be easily introduced in the Linux
+community. All the CD-player authors will have to be informed, we can
+even send in our own patches to the programs. The use of *O_NONBLOCK*
+has most likely no influence on the behavior of the CD-players on
+other operating systems than Linux. Finally, a user can always revert
+to old behavior by a call to
+*ioctl(file_descriptor, CDROM_CLEAR_OPTIONS, CDO_USE_FFLAGS)*.
+
+The preferred strategy of *open()*
+----------------------------------
+
+The routines in `cdrom.c` are designed in such a way that run-time
+configuration of the behavior of CD-ROM devices (of **any** type)
+can be carried out, by the *CDROM_SET/CLEAR_OPTIONS* *ioctls*. Thus, various
+modes of operation can be set:
+
+`CDO_AUTO_CLOSE | CDO_USE_FFLAGS | CDO_LOCK`
+   This is the default setting. (With *CDO_CHECK_TYPE* it will be better, in
+   the future.) If the device is not yet opened by any other process, and if
+   the device is being opened for data (*O_NONBLOCK* is not set) and the
+   tray is found to be open, an attempt to close the tray is made. Then,
+   it is verified that a disc is in the drive and, if *CDO_CHECK_TYPE* is
+   set, that it contains tracks of type `data mode 1`. Only if all tests
+   are passed is the return value zero. The door is locked to prevent file
+   system corruption. If the drive is opened for audio (*O_NONBLOCK* is
+   set), no actions are taken and a value of 0 will be returned.
+
+`CDO_AUTO_CLOSE | CDO_AUTO_EJECT | CDO_LOCK`
+   This mimics the behavior of the current sbpcd-driver. The option flags are
+   ignored, the tray is closed on the first open, if necessary. Similarly,
+   the tray is opened on the last release, i. e., if a CD-ROM is unmounted,
+   it is automatically ejected, such that the user can replace it.
+
+We hope that these option can convince everybody (both driver
+maintainers and user program developers) to adopt the new CD-ROM
+driver scheme and option flag interpretation.
+
+Description of routines in `cdrom.c`
+====================================
+
+Only a few routines in `cdrom.c` are exported to the drivers. In this
+new section we will discuss these, as well as the functions that `take
+over` the CD-ROM interface to the kernel. The header file belonging
+to `cdrom.c` is called `cdrom.h`. Formerly, some of the contents of this
+file were placed in the file `ucdrom.h`, but this file has now been
+merged back into `cdrom.h`.
+
+::
+
+	struct file_operations cdrom_fops
+
+The contents of this structure were described in cdrom_api_.
+A pointer to this structure is assigned to the *fops* field
+of the *struct gendisk*.
+
+::
+
+	int register_cdrom(struct cdrom_device_info *cdi)
+
+This function is used in about the same way one registers *cdrom_fops*
+with the kernel, the device operations and information structures,
+as described in cdrom_api_, should be registered with the
+Uniform CD-ROM Driver::
+
+	register_cdrom(&<device>_info);
+
+
+This function returns zero upon success, and non-zero upon
+failure. The structure *<device>_info* should have a pointer to the
+driver's *<device>_dops*, as in::
+
+	struct cdrom_device_info <device>_info = {
+		<device>_dops;
+		...
+	}
+
+Note that a driver must have one static structure, *<device>_dops*, while
+it may have as many structures *<device>_info* as there are minor devices
+active. *Register_cdrom()* builds a linked list from these.
+
+
+::
+
+	void unregister_cdrom(struct cdrom_device_info *cdi)
+
+Unregistering device *cdi* with minor number *MINOR(cdi->dev)* removes
+the minor device from the list. If it was the last registered minor for
+the low-level driver, this disconnects the registered device-operation
+routines from the CD-ROM interface. This function returns zero upon
+success, and non-zero upon failure.
+
+::
+
+	int cdrom_open(struct inode * ip, struct file * fp)
+
+This function is not called directly by the low-level drivers, it is
+listed in the standard *cdrom_fops*. If the VFS opens a file, this
+function becomes active. A strategy is implemented in this routine,
+taking care of all capabilities and options that are set in the
+*cdrom_device_ops* connected to the device. Then, the program flow is
+transferred to the device_dependent *open()* call.
+
+::
+
+	void cdrom_release(struct inode *ip, struct file *fp)
+
+This function implements the reverse-logic of *cdrom_open()*, and then
+calls the device-dependent *release()* routine. When the use-count has
+reached 0, the allocated buffers are flushed by calls to *sync_dev(dev)*
+and *invalidate_buffers(dev)*.
+
+
+.. _cdrom_ioctl:
+
+::
+
+	int cdrom_ioctl(struct inode *ip, struct file *fp,
+			unsigned int cmd, unsigned long arg)
+
+This function handles all the standard *ioctl* requests for CD-ROM
+devices in a uniform way. The different calls fall into three
+categories: *ioctl()'s* that can be directly implemented by device
+operations, ones that are routed through the call *audio_ioctl()*, and
+the remaining ones, that are presumable device-dependent. Generally, a
+negative return value indicates an error.
+
+Directly implemented *ioctl()'s*
+--------------------------------
+
+The following `old` CD-ROM *ioctl()*\ 's are implemented by directly
+calling device-operations in *cdrom_device_ops*, if implemented and
+not masked:
+
+`CDROMMULTISESSION`
+	Requests the last session on a CD-ROM.
+`CDROMEJECT`
+	Open tray.
+`CDROMCLOSETRAY`
+	Close tray.
+`CDROMEJECT_SW`
+	If *arg\not=0*, set behavior to auto-close (close
+	tray on first open) and auto-eject (eject on last release), otherwise
+	set behavior to non-moving on *open()* and *release()* calls.
+`CDROM_GET_MCN`
+	Get the Media Catalog Number from a CD.
+
+*Ioctl*s routed through *audio_ioctl()*
+---------------------------------------
+
+The following set of *ioctl()'s* are all implemented through a call to
+the *cdrom_fops* function *audio_ioctl()*. Memory checks and
+allocation are performed in *cdrom_ioctl()*, and also sanitization of
+address format (*CDROM_LBA*/*CDROM_MSF*) is done.
+
+`CDROMSUBCHNL`
+	Get sub-channel data in argument *arg* of type
+	`struct cdrom_subchnl *`.
+`CDROMREADTOCHDR`
+	Read Table of Contents header, in *arg* of type
+	`struct cdrom_tochdr *`.
+`CDROMREADTOCENTRY`
+	Read a Table of Contents entry in *arg* and specified by *arg*
+	of type `struct cdrom_tocentry *`.
+`CDROMPLAYMSF`
+	Play audio fragment specified in Minute, Second, Frame format,
+	delimited by *arg* of type `struct cdrom_msf *`.
+`CDROMPLAYTRKIND`
+	Play audio fragment in track-index format delimited by *arg*
+	of type `struct cdrom_ti *`.
+`CDROMVOLCTRL`
+	Set volume specified by *arg* of type `struct cdrom_volctrl *`.
+`CDROMVOLREAD`
+	Read volume into by *arg* of type `struct cdrom_volctrl *`.
+`CDROMSTART`
+	Spin up disc.
+`CDROMSTOP`
+	Stop playback of audio fragment.
+`CDROMPAUSE`
+	Pause playback of audio fragment.
+`CDROMRESUME`
+	Resume playing.
+
+New *ioctl()'s* in `cdrom.c`
+----------------------------
+
+The following *ioctl()'s* have been introduced to allow user programs to
+control the behavior of individual CD-ROM devices. New *ioctl*
+commands can be identified by the underscores in their names.
+
+`CDROM_SET_OPTIONS`
+	Set options specified by *arg*. Returns the option flag register
+	after modification. Use *arg = \rm0* for reading the current flags.
+`CDROM_CLEAR_OPTIONS`
+	Clear options specified by *arg*. Returns the option flag register
+	after modification.
+`CDROM_SELECT_SPEED`
+	Select head-rate speed of disc specified as by *arg* in units
+	of standard cdrom speed (176\,kB/sec raw data or
+	150kB/sec file system data). The value 0 means `auto-select`,
+	i. e., play audio discs at real time and data discs at maximum speed.
+	The value *arg* is checked against the maximum head rate of the
+	drive found in the *cdrom_dops*.
+`CDROM_SELECT_DISC`
+	Select disc numbered *arg* from a juke-box.
+
+	First disc is numbered 0. The number *arg* is checked against the
+	maximum number of discs in the juke-box found in the *cdrom_dops*.
+`CDROM_MEDIA_CHANGED`
+	Returns 1 if a disc has been changed since the last call.
+	For juke-boxes, an extra argument *arg*
+	specifies the slot for which the information is given. The special
+	value *CDSL_CURRENT* requests that information about the currently
+	selected slot be returned.
+`CDROM_DRIVE_STATUS`
+	Returns the status of the drive by a call to
+	*drive_status()*. Return values are defined in cdrom_drive_status_.
+	Note that this call doesn't return information on the
+	current playing activity of the drive; this can be polled through
+	an *ioctl* call to *CDROMSUBCHNL*. For juke-boxes, an extra argument
+	*arg* specifies the slot for which (possibly limited) information is
+	given. The special value *CDSL_CURRENT* requests that information
+	about the currently selected slot be returned.
+`CDROM_DISC_STATUS`
+	Returns the type of the disc currently in the drive.
+	It should be viewed as a complement to *CDROM_DRIVE_STATUS*.
+	This *ioctl* can provide *some* information about the current
+	disc that is inserted in the drive. This functionality used to be
+	implemented in the low level drivers, but is now carried out
+	entirely in Uniform CD-ROM Driver.
+
+	The history of development of the CD's use as a carrier medium for
+	various digital information has lead to many different disc types.
+	This *ioctl* is useful only in the case that CDs have \emph {only
+	one} type of data on them. While this is often the case, it is
+	also very common for CDs to have some tracks with data, and some
+	tracks with audio. Because this is an existing interface, rather
+	than fixing this interface by changing the assumptions it was made
+	under, thereby breaking all user applications that use this
+	function, the Uniform CD-ROM Driver implements this *ioctl* as
+	follows: If the CD in question has audio tracks on it, and it has
+	absolutely no CD-I, XA, or data tracks on it, it will be reported
+	as *CDS_AUDIO*. If it has both audio and data tracks, it will
+	return *CDS_MIXED*. If there are no audio tracks on the disc, and
+	if the CD in question has any CD-I tracks on it, it will be
+	reported as *CDS_XA_2_2*. Failing that, if the CD in question
+	has any XA tracks on it, it will be reported as *CDS_XA_2_1*.
+	Finally, if the CD in question has any data tracks on it,
+	it will be reported as a data CD (*CDS_DATA_1*).
+
+	This *ioctl* can return::
+
+		CDS_NO_INFO	/* no information available */
+		CDS_NO_DISC	/* no disc is inserted, or tray is opened */
+		CDS_AUDIO	/* Audio disc (2352 audio bytes/frame) */
+		CDS_DATA_1	/* data disc, mode 1 (2048 user bytes/frame) */
+		CDS_XA_2_1	/* mixed data (XA), mode 2, form 1 (2048 user bytes) */
+		CDS_XA_2_2	/* mixed data (XA), mode 2, form 1 (2324 user bytes) */
+		CDS_MIXED	/* mixed audio/data disc */
+
+	For some information concerning frame layout of the various disc
+	types, see a recent version of `cdrom.h`.
+
+`CDROM_CHANGER_NSLOTS`
+	Returns the number of slots in a juke-box.
+`CDROMRESET`
+	Reset the drive.
+`CDROM_GET_CAPABILITY`
+	Returns the *capability* flags for the drive. Refer to section
+	cdrom_capabilities_ for more information on these flags.
+`CDROM_LOCKDOOR`
+	 Locks the door of the drive. `arg == 0` unlocks the door,
+	 any other value locks it.
+`CDROM_DEBUG`
+	 Turns on debugging info. Only root is allowed to do this.
+	 Same semantics as CDROM_LOCKDOOR.
+
+
+Device dependent *ioctl()'s*
+----------------------------
+
+Finally, all other *ioctl()'s* are passed to the function *dev_ioctl()*,
+if implemented. No memory allocation or verification is carried out.
+
+How to update your driver
+=========================
+
+- Make a backup of your current driver.
+- Get hold of the files `cdrom.c` and `cdrom.h`, they should be in
+  the directory tree that came with this documentation.
+- Make sure you include `cdrom.h`.
+- Change the 3rd argument of *register_blkdev* from `&<your-drive>_fops`
+  to `&cdrom_fops`.
+- Just after that line, add the following to register with the Uniform
+  CD-ROM Driver::
+
+	register_cdrom(&<your-drive>_info);*
+
+  Similarly, add a call to *unregister_cdrom()* at the appropriate place.
+- Copy an example of the device-operations *struct* to your
+  source, e. g., from `cm206.c` *cm206_dops*, and change all
+  entries to names corresponding to your driver, or names you just
+  happen to like. If your driver doesn't support a certain function,
+  make the entry *NULL*. At the entry *capability* you should list all
+  capabilities your driver currently supports. If your driver
+  has a capability that is not listed, please send me a message.
+- Copy the *cdrom_device_info* declaration from the same example
+  driver, and modify the entries according to your needs. If your
+  driver dynamically determines the capabilities of the hardware, this
+  structure should also be declared dynamically.
+- Implement all functions in your `<device>_dops` structure,
+  according to prototypes listed in  `cdrom.h`, and specifications given
+  in cdrom_api_. Most likely you have already implemented
+  the code in a large part, and you will almost certainly need to adapt the
+  prototype and return values.
+- Rename your `<device>_ioctl()` function to *audio_ioctl* and
+  change the prototype a little. Remove entries listed in the first
+  part in cdrom_ioctl_, if your code was OK, these are
+  just calls to the routines you adapted in the previous step.
+- You may remove all remaining memory checking code in the
+  *audio_ioctl()* function that deals with audio commands (these are
+  listed in the second part of cdrom_ioctl_. There is no
+  need for memory allocation either, so most *case*s in the *switch*
+  statement look similar to::
+
+	case CDROMREADTOCENTRY:
+		get_toc_entry\bigl((struct cdrom_tocentry *) arg);
+
+- All remaining *ioctl* cases must be moved to a separate
+  function, *<device>_ioctl*, the device-dependent *ioctl()'s*. Note that
+  memory checking and allocation must be kept in this code!
+- Change the prototypes of *<device>_open()* and
+  *<device>_release()*, and remove any strategic code (i. e., tray
+  movement, door locking, etc.).
+- Try to recompile the drivers. We advise you to use modules, both
+  for `cdrom.o` and your driver, as debugging is much easier this
+  way.
+
+Thanks
+======
+
+Thanks to all the people involved. First, Erik Andersen, who has
+taken over the torch in maintaining `cdrom.c` and integrating much
+CD-ROM-related code in the 2.1-kernel. Thanks to Scott Snyder and
+Gerd Knorr, who were the first to implement this interface for SCSI
+and IDE-CD drivers and added many ideas for extension of the data
+structures relative to kernel~2.0. Further thanks to Heiko Eißfeldt,
+Thomas Quinot, Jon Tombs, Ken Pizzini, Eberhard Mönkeberg and Andrew Kroll,
+the Linux CD-ROM device driver developers who were kind
+enough to give suggestions and criticisms during the writing. Finally
+of course, I want to thank Linus Torvalds for making this possible in
+the first place.
diff --git a/Documentation/cdrom/ide-cd.rst b/Documentation/cdrom/ide-cd.rst
new file mode 100644
index 000000000..bdccb74fc
--- /dev/null
+++ b/Documentation/cdrom/ide-cd.rst
@@ -0,0 +1,538 @@
+IDE-CD driver documentation
+===========================
+
+:Originally by: scott snyder  <snyder@fnald0.fnal.gov> (19 May 1996)
+:Carrying on the torch is: Erik Andersen <andersee@debian.org>
+:New maintainers (19 Oct 1998): Jens Axboe <axboe@image.dk>
+
+1. Introduction
+---------------
+
+The ide-cd driver should work with all ATAPI ver 1.2 to ATAPI 2.6 compliant
+CDROM drives which attach to an IDE interface.  Note that some CDROM vendors
+(including Mitsumi, Sony, Creative, Aztech, and Goldstar) have made
+both ATAPI-compliant drives and drives which use a proprietary
+interface.  If your drive uses one of those proprietary interfaces,
+this driver will not work with it (but one of the other CDROM drivers
+probably will).  This driver will not work with `ATAPI` drives which
+attach to the parallel port.  In addition, there is at least one drive
+(CyCDROM CR520ie) which attaches to the IDE port but is not ATAPI;
+this driver will not work with drives like that either (but see the
+aztcd driver).
+
+This driver provides the following features:
+
+ - Reading from data tracks, and mounting ISO 9660 filesystems.
+
+ - Playing audio tracks.  Most of the CDROM player programs floating
+   around should work; I usually use Workman.
+
+ - Multisession support.
+
+ - On drives which support it, reading digital audio data directly
+   from audio tracks.  The program cdda2wav can be used for this.
+   Note, however, that only some drives actually support this.
+
+ - There is now support for CDROM changers which comply with the
+   ATAPI 2.6 draft standard (such as the NEC CDR-251).  This additional
+   functionality includes a function call to query which slot is the
+   currently selected slot, a function call to query which slots contain
+   CDs, etc. A sample program which demonstrates this functionality is
+   appended to the end of this file.  The Sanyo 3-disc changer
+   (which does not conform to the standard) is also now supported.
+   Please note the driver refers to the first CD as slot # 0.
+
+
+2. Installation
+---------------
+
+0. The ide-cd relies on the ide disk driver.  See
+   Documentation/ide/ide.rst for up-to-date information on the ide
+   driver.
+
+1. Make sure that the ide and ide-cd drivers are compiled into the
+   kernel you're using.  When configuring the kernel, in the section
+   entitled "Floppy, IDE, and other block devices", say either `Y`
+   (which will compile the support directly into the kernel) or `M`
+   (to compile support as a module which can be loaded and unloaded)
+   to the options::
+
+      ATA/ATAPI/MFM/RLL support
+      Include IDE/ATAPI CDROM support
+
+   Depending on what type of IDE interface you have, you may need to
+   specify additional configuration options.  See
+   Documentation/ide/ide.rst.
+
+2. You should also ensure that the iso9660 filesystem is either
+   compiled into the kernel or available as a loadable module.  You
+   can see if a filesystem is known to the kernel by catting
+   /proc/filesystems.
+
+3. The CDROM drive should be connected to the host on an IDE
+   interface.  Each interface on a system is defined by an I/O port
+   address and an IRQ number, the standard assignments being
+   0x1f0 and 14 for the primary interface and 0x170 and 15 for the
+   secondary interface.  Each interface can control up to two devices,
+   where each device can be a hard drive, a CDROM drive, a floppy drive,
+   or a tape drive.  The two devices on an interface are called `master`
+   and `slave`; this is usually selectable via a jumper on the drive.
+
+   Linux names these devices as follows.  The master and slave devices
+   on the primary IDE interface are called `hda` and `hdb`,
+   respectively.  The drives on the secondary interface are called
+   `hdc` and `hdd`.  (Interfaces at other locations get other letters
+   in the third position; see Documentation/ide/ide.rst.)
+
+   If you want your CDROM drive to be found automatically by the
+   driver, you should make sure your IDE interface uses either the
+   primary or secondary addresses mentioned above.  In addition, if
+   the CDROM drive is the only device on the IDE interface, it should
+   be jumpered as `master`.  (If for some reason you cannot configure
+   your system in this manner, you can probably still use the driver.
+   You may have to pass extra configuration information to the kernel
+   when you boot, however.  See Documentation/ide/ide.rst for more
+   information.)
+
+4. Boot the system.  If the drive is recognized, you should see a
+   message which looks like::
+
+     hdb: NEC CD-ROM DRIVE:260, ATAPI CDROM drive
+
+   If you do not see this, see section 5 below.
+
+5. You may want to create a symbolic link /dev/cdrom pointing to the
+   actual device.  You can do this with the command::
+
+     ln -s  /dev/hdX  /dev/cdrom
+
+   where X should be replaced by the letter indicating where your
+   drive is installed.
+
+6. You should be able to see any error messages from the driver with
+   the `dmesg` command.
+
+
+3. Basic usage
+--------------
+
+An ISO 9660 CDROM can be mounted by putting the disc in the drive and
+typing (as root)::
+
+  mount -t iso9660 /dev/cdrom /mnt/cdrom
+
+where it is assumed that /dev/cdrom is a link pointing to the actual
+device (as described in step 5 of the last section) and /mnt/cdrom is
+an empty directory.  You should now be able to see the contents of the
+CDROM under the /mnt/cdrom directory.  If you want to eject the CDROM,
+you must first dismount it with a command like::
+
+  umount /mnt/cdrom
+
+Note that audio CDs cannot be mounted.
+
+Some distributions set up /etc/fstab to always try to mount a CDROM
+filesystem on bootup.  It is not required to mount the CDROM in this
+manner, though, and it may be a nuisance if you change CDROMs often.
+You should feel free to remove the cdrom line from /etc/fstab and
+mount CDROMs manually if that suits you better.
+
+Multisession and photocd discs should work with no special handling.
+The hpcdtoppm package (ftp.gwdg.de:/pub/linux/hpcdtoppm/) may be
+useful for reading photocds.
+
+To play an audio CD, you should first unmount and remove any data
+CDROM.  Any of the CDROM player programs should then work (workman,
+workbone, cdplayer, etc.).
+
+On a few drives, you can read digital audio directly using a program
+such as cdda2wav.  The only types of drive which I've heard support
+this are Sony and Toshiba drives.  You will get errors if you try to
+use this function on a drive which does not support it.
+
+For supported changers, you can use the `cdchange` program (appended to
+the end of this file) to switch between changer slots.  Note that the
+drive should be unmounted before attempting this.  The program takes
+two arguments:  the CDROM device, and the slot number to which you wish
+to change.  If the slot number is -1, the drive is unloaded.
+
+
+4. Common problems
+------------------
+
+This section discusses some common problems encountered when trying to
+use the driver, and some possible solutions.  Note that if you are
+experiencing problems, you should probably also review
+Documentation/ide/ide.rst for current information about the underlying
+IDE support code.  Some of these items apply only to earlier versions
+of the driver, but are mentioned here for completeness.
+
+In most cases, you should probably check with `dmesg` for any errors
+from the driver.
+
+a. Drive is not detected during booting.
+
+   - Review the configuration instructions above and in
+     Documentation/ide/ide.rst, and check how your hardware is
+     configured.
+
+   - If your drive is the only device on an IDE interface, it should
+     be jumpered as master, if at all possible.
+
+   - If your IDE interface is not at the standard addresses of 0x170
+     or 0x1f0, you'll need to explicitly inform the driver using a
+     lilo option.  See Documentation/ide/ide.rst.  (This feature was
+     added around kernel version 1.3.30.)
+
+   - If the autoprobing is not finding your drive, you can tell the
+     driver to assume that one exists by using a lilo option of the
+     form `hdX=cdrom`, where X is the drive letter corresponding to
+     where your drive is installed.  Note that if you do this and you
+     see a boot message like::
+
+       hdX: ATAPI cdrom (?)
+
+     this does _not_ mean that the driver has successfully detected
+     the drive; rather, it means that the driver has not detected a
+     drive, but is assuming there's one there anyway because you told
+     it so.  If you actually try to do I/O to a drive defined at a
+     nonexistent or nonresponding I/O address, you'll probably get
+     errors with a status value of 0xff.
+
+   - Some IDE adapters require a nonstandard initialization sequence
+     before they'll function properly.  (If this is the case, there
+     will often be a separate MS-DOS driver just for the controller.)
+     IDE interfaces on sound cards often fall into this category.
+
+     Support for some interfaces needing extra initialization is
+     provided in later 1.3.x kernels.  You may need to turn on
+     additional kernel configuration options to get them to work;
+     see Documentation/ide/ide.rst.
+
+     Even if support is not available for your interface, you may be
+     able to get it to work with the following procedure.  First boot
+     MS-DOS and load the appropriate drivers.  Then warm-boot linux
+     (i.e., without powering off).  If this works, it can be automated
+     by running loadlin from the MS-DOS autoexec.
+
+
+b. Timeout/IRQ errors.
+
+  - If you always get timeout errors, interrupts from the drive are
+    probably not making it to the host.
+
+  - IRQ problems may also be indicated by the message
+    `IRQ probe failed (<n>)` while booting.  If <n> is zero, that
+    means that the system did not see an interrupt from the drive when
+    it was expecting one (on any feasible IRQ).  If <n> is negative,
+    that means the system saw interrupts on multiple IRQ lines, when
+    it was expecting to receive just one from the CDROM drive.
+
+  - Double-check your hardware configuration to make sure that the IRQ
+    number of your IDE interface matches what the driver expects.
+    (The usual assignments are 14 for the primary (0x1f0) interface
+    and 15 for the secondary (0x170) interface.)  Also be sure that
+    you don't have some other hardware which might be conflicting with
+    the IRQ you're using.  Also check the BIOS setup for your system;
+    some have the ability to disable individual IRQ levels, and I've
+    had one report of a system which was shipped with IRQ 15 disabled
+    by default.
+
+  - Note that many MS-DOS CDROM drivers will still function even if
+    there are hardware problems with the interrupt setup; they
+    apparently don't use interrupts.
+
+  - If you own a Pioneer DR-A24X, you _will_ get nasty error messages
+    on boot such as "irq timeout: status=0x50 { DriveReady SeekComplete }"
+    The Pioneer DR-A24X CDROM drives are fairly popular these days.
+    Unfortunately, these drives seem to become very confused when we perform
+    the standard Linux ATA disk drive probe. If you own one of these drives,
+    you can bypass the ATA probing which confuses these CDROM drives, by
+    adding `append="hdX=noprobe hdX=cdrom"` to your lilo.conf file and running
+    lilo (again where X is the drive letter corresponding to where your drive
+    is installed.)
+
+c. System hangups.
+
+  - If the system locks up when you try to access the CDROM, the most
+    likely cause is that you have a buggy IDE adapter which doesn't
+    properly handle simultaneous transactions on multiple interfaces.
+    The most notorious of these is the CMD640B chip.  This problem can
+    be worked around by specifying the `serialize` option when
+    booting.  Recent kernels should be able to detect the need for
+    this automatically in most cases, but the detection is not
+    foolproof.  See Documentation/ide/ide.rst for more information
+    about the `serialize` option and the CMD640B.
+
+  - Note that many MS-DOS CDROM drivers will work with such buggy
+    hardware, apparently because they never attempt to overlap CDROM
+    operations with other disk activity.
+
+
+d. Can't mount a CDROM.
+
+  - If you get errors from mount, it may help to check `dmesg` to see
+    if there are any more specific errors from the driver or from the
+    filesystem.
+
+  - Make sure there's a CDROM loaded in the drive, and that's it's an
+    ISO 9660 disc.  You can't mount an audio CD.
+
+  - With the CDROM in the drive and unmounted, try something like::
+
+      cat /dev/cdrom | od | more
+
+    If you see a dump, then the drive and driver are probably working
+    OK, and the problem is at the filesystem level (i.e., the CDROM is
+    not ISO 9660 or has errors in the filesystem structure).
+
+  - If you see `not a block device` errors, check that the definitions
+    of the device special files are correct.  They should be as
+    follows::
+
+      brw-rw----   1 root     disk       3,   0 Nov 11 18:48 /dev/hda
+      brw-rw----   1 root     disk       3,  64 Nov 11 18:48 /dev/hdb
+      brw-rw----   1 root     disk      22,   0 Nov 11 18:48 /dev/hdc
+      brw-rw----   1 root     disk      22,  64 Nov 11 18:48 /dev/hdd
+
+    Some early Slackware releases had these defined incorrectly.  If
+    these are wrong, you can remake them by running the script
+    scripts/MAKEDEV.ide.  (You may have to make it executable
+    with chmod first.)
+
+    If you have a /dev/cdrom symbolic link, check that it is pointing
+    to the correct device file.
+
+    If you hear people talking of the devices `hd1a` and `hd1b`, these
+    were old names for what are now called hdc and hdd.  Those names
+    should be considered obsolete.
+
+  - If mount is complaining that the iso9660 filesystem is not
+    available, but you know it is (check /proc/filesystems), you
+    probably need a newer version of mount.  Early versions would not
+    always give meaningful error messages.
+
+
+e. Directory listings are unpredictably truncated, and `dmesg` shows
+   `buffer botch` error messages from the driver.
+
+  - There was a bug in the version of the driver in 1.2.x kernels
+    which could cause this.  It was fixed in 1.3.0.  If you can't
+    upgrade, you can probably work around the problem by specifying a
+    blocksize of 2048 when mounting.  (Note that you won't be able to
+    directly execute binaries off the CDROM in that case.)
+
+    If you see this in kernels later than 1.3.0, please report it as a
+    bug.
+
+
+f. Data corruption.
+
+  - Random data corruption was occasionally observed with the Hitachi
+    CDR-7730 CDROM. If you experience data corruption, using "hdx=slow"
+    as a command line parameter may work around the problem, at the
+    expense of low system performance.
+
+
+5. cdchange.c
+-------------
+
+::
+
+  /*
+   * cdchange.c  [-v]  <device>  [<slot>]
+   *
+   * This loads a CDROM from a specified slot in a changer, and displays
+   * information about the changer status.  The drive should be unmounted before
+   * using this program.
+   *
+   * Changer information is displayed if either the -v flag is specified
+   * or no slot was specified.
+   *
+   * Based on code originally from Gerhard Zuber <zuber@berlin.snafu.de>.
+   * Changer status information, and rewrite for the new Uniform CDROM driver
+   * interface by Erik Andersen <andersee@debian.org>.
+   */
+
+  #include <stdio.h>
+  #include <stdlib.h>
+  #include <errno.h>
+  #include <string.h>
+  #include <unistd.h>
+  #include <fcntl.h>
+  #include <sys/ioctl.h>
+  #include <linux/cdrom.h>
+
+
+  int
+  main (int argc, char **argv)
+  {
+	char *program;
+	char *device;
+	int fd;           /* file descriptor for CD-ROM device */
+	int status;       /* return status for system calls */
+	int verbose = 0;
+	int slot=-1, x_slot;
+	int total_slots_available;
+
+	program = argv[0];
+
+	++argv;
+	--argc;
+
+	if (argc < 1 || argc > 3) {
+		fprintf (stderr, "usage: %s [-v] <device> [<slot>]\n",
+			 program);
+		fprintf (stderr, "       Slots are numbered 1 -- n.\n");
+		exit (1);
+	}
+
+       if (strcmp (argv[0], "-v") == 0) {
+                verbose = 1;
+                ++argv;
+                --argc;
+        }
+
+	device = argv[0];
+
+	if (argc == 2)
+		slot = atoi (argv[1]) - 1;
+
+	/* open device */
+	fd = open(device, O_RDONLY | O_NONBLOCK);
+	if (fd < 0) {
+		fprintf (stderr, "%s: open failed for `%s`: %s\n",
+			 program, device, strerror (errno));
+		exit (1);
+	}
+
+	/* Check CD player status */
+	total_slots_available = ioctl (fd, CDROM_CHANGER_NSLOTS);
+	if (total_slots_available <= 1 ) {
+		fprintf (stderr, "%s: Device `%s` is not an ATAPI "
+			"compliant CD changer.\n", program, device);
+		exit (1);
+	}
+
+	if (slot >= 0) {
+		if (slot >= total_slots_available) {
+			fprintf (stderr, "Bad slot number.  "
+				 "Should be 1 -- %d.\n",
+				 total_slots_available);
+			exit (1);
+		}
+
+		/* load */
+		slot=ioctl (fd, CDROM_SELECT_DISC, slot);
+		if (slot<0) {
+			fflush(stdout);
+				perror ("CDROM_SELECT_DISC ");
+			exit(1);
+		}
+	}
+
+	if (slot < 0 || verbose) {
+
+		status=ioctl (fd, CDROM_SELECT_DISC, CDSL_CURRENT);
+		if (status<0) {
+			fflush(stdout);
+			perror (" CDROM_SELECT_DISC");
+			exit(1);
+		}
+		slot=status;
+
+		printf ("Current slot: %d\n", slot+1);
+		printf ("Total slots available: %d\n",
+			total_slots_available);
+
+		printf ("Drive status: ");
+                status = ioctl (fd, CDROM_DRIVE_STATUS, CDSL_CURRENT);
+                if (status<0) {
+                  perror(" CDROM_DRIVE_STATUS");
+                } else switch(status) {
+		case CDS_DISC_OK:
+			printf ("Ready.\n");
+			break;
+		case CDS_TRAY_OPEN:
+			printf ("Tray Open.\n");
+			break;
+		case CDS_DRIVE_NOT_READY:
+			printf ("Drive Not Ready.\n");
+			break;
+		default:
+			printf ("This Should not happen!\n");
+			break;
+		}
+
+		for (x_slot=0; x_slot<total_slots_available; x_slot++) {
+			printf ("Slot %2d: ", x_slot+1);
+			status = ioctl (fd, CDROM_DRIVE_STATUS, x_slot);
+			if (status<0) {
+			     perror(" CDROM_DRIVE_STATUS");
+			} else switch(status) {
+			case CDS_DISC_OK:
+				printf ("Disc present.");
+				break;
+			case CDS_NO_DISC:
+				printf ("Empty slot.");
+				break;
+			case CDS_TRAY_OPEN:
+				printf ("CD-ROM tray open.\n");
+				break;
+			case CDS_DRIVE_NOT_READY:
+				printf ("CD-ROM drive not ready.\n");
+				break;
+			case CDS_NO_INFO:
+				printf ("No Information available.");
+				break;
+			default:
+				printf ("This Should not happen!\n");
+				break;
+			}
+		  if (slot == x_slot) {
+                  status = ioctl (fd, CDROM_DISC_STATUS);
+                  if (status<0) {
+			perror(" CDROM_DISC_STATUS");
+                  }
+		  switch (status) {
+			case CDS_AUDIO:
+				printf ("\tAudio disc.\t");
+				break;
+			case CDS_DATA_1:
+			case CDS_DATA_2:
+				printf ("\tData disc type %d.\t", status-CDS_DATA_1+1);
+				break;
+			case CDS_XA_2_1:
+			case CDS_XA_2_2:
+				printf ("\tXA data disc type %d.\t", status-CDS_XA_2_1+1);
+				break;
+			default:
+				printf ("\tUnknown disc type 0x%x!\t", status);
+				break;
+			}
+			}
+			status = ioctl (fd, CDROM_MEDIA_CHANGED, x_slot);
+			if (status<0) {
+				perror(" CDROM_MEDIA_CHANGED");
+			}
+			switch (status) {
+			case 1:
+				printf ("Changed.\n");
+				break;
+			default:
+				printf ("\n");
+				break;
+			}
+		}
+	}
+
+	/* close device */
+	status = close (fd);
+	if (status != 0) {
+		fprintf (stderr, "%s: close failed for `%s`: %s\n",
+			 program, device, strerror (errno));
+		exit (1);
+	}
+
+	exit (0);
+  }
diff --git a/Documentation/cdrom/index.rst b/Documentation/cdrom/index.rst
new file mode 100644
index 000000000..338ad5f94
--- /dev/null
+++ b/Documentation/cdrom/index.rst
@@ -0,0 +1,19 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+=====
+cdrom
+=====
+
+.. toctree::
+    :maxdepth: 1
+
+    cdrom-standard
+    ide-cd
+    packet-writing
+
+.. only::  subproject and html
+
+   Indices
+   =======
+
+   * :ref:`genindex`
diff --git a/Documentation/cdrom/packet-writing.rst b/Documentation/cdrom/packet-writing.rst
new file mode 100644
index 000000000..c5c957195
--- /dev/null
+++ b/Documentation/cdrom/packet-writing.rst
@@ -0,0 +1,139 @@
+==============
+Packet writing
+==============
+
+Getting started quick
+---------------------
+
+- Select packet support in the block device section and UDF support in
+  the file system section.
+
+- Compile and install kernel and modules, reboot.
+
+- You need the udftools package (pktsetup, mkudffs, cdrwtool).
+  Download from http://sourceforge.net/projects/linux-udf/
+
+- Grab a new CD-RW disc and format it (assuming CD-RW is hdc, substitute
+  as appropriate)::
+
+	# cdrwtool -d /dev/hdc -q
+
+- Setup your writer::
+
+	# pktsetup dev_name /dev/hdc
+
+- Now you can mount /dev/pktcdvd/dev_name and copy files to it. Enjoy::
+
+	# mount /dev/pktcdvd/dev_name /cdrom -t udf -o rw,noatime
+
+
+Packet writing for DVD-RW media
+-------------------------------
+
+DVD-RW discs can be written to much like CD-RW discs if they are in
+the so called "restricted overwrite" mode. To put a disc in restricted
+overwrite mode, run::
+
+	# dvd+rw-format /dev/hdc
+
+You can then use the disc the same way you would use a CD-RW disc::
+
+	# pktsetup dev_name /dev/hdc
+	# mount /dev/pktcdvd/dev_name /cdrom -t udf -o rw,noatime
+
+
+Packet writing for DVD+RW media
+-------------------------------
+
+According to the DVD+RW specification, a drive supporting DVD+RW discs
+shall implement "true random writes with 2KB granularity", which means
+that it should be possible to put any filesystem with a block size >=
+2KB on such a disc. For example, it should be possible to do::
+
+	# dvd+rw-format /dev/hdc   (only needed if the disc has never
+	                            been formatted)
+	# mkudffs /dev/hdc
+	# mount /dev/hdc /cdrom -t udf -o rw,noatime
+
+However, some drives don't follow the specification and expect the
+host to perform aligned writes at 32KB boundaries. Other drives do
+follow the specification, but suffer bad performance problems if the
+writes are not 32KB aligned.
+
+Both problems can be solved by using the pktcdvd driver, which always
+generates aligned writes::
+
+	# dvd+rw-format /dev/hdc
+	# pktsetup dev_name /dev/hdc
+	# mkudffs /dev/pktcdvd/dev_name
+	# mount /dev/pktcdvd/dev_name /cdrom -t udf -o rw,noatime
+
+
+Packet writing for DVD-RAM media
+--------------------------------
+
+DVD-RAM discs are random writable, so using the pktcdvd driver is not
+necessary. However, using the pktcdvd driver can improve performance
+in the same way it does for DVD+RW media.
+
+
+Notes
+-----
+
+- CD-RW media can usually not be overwritten more than about 1000
+  times, so to avoid unnecessary wear on the media, you should always
+  use the noatime mount option.
+
+- Defect management (ie automatic remapping of bad sectors) has not
+  been implemented yet, so you are likely to get at least some
+  filesystem corruption if the disc wears out.
+
+- Since the pktcdvd driver makes the disc appear as a regular block
+  device with a 2KB block size, you can put any filesystem you like on
+  the disc. For example, run::
+
+	# /sbin/mke2fs /dev/pktcdvd/dev_name
+
+  to create an ext2 filesystem on the disc.
+
+
+Using the pktcdvd sysfs interface
+---------------------------------
+
+Since Linux 2.6.20, the pktcdvd module has a sysfs interface
+and can be controlled by it. For example the "pktcdvd" tool uses
+this interface. (see http://tom.ist-im-web.de/download/pktcdvd )
+
+"pktcdvd" works similar to "pktsetup", e.g.::
+
+	# pktcdvd -a dev_name /dev/hdc
+	# mkudffs /dev/pktcdvd/dev_name
+	# mount -t udf -o rw,noatime /dev/pktcdvd/dev_name /dvdram
+	# cp files /dvdram
+	# umount /dvdram
+	# pktcdvd -r dev_name
+
+
+For a description of the sysfs interface look into the file:
+
+  Documentation/ABI/testing/sysfs-class-pktcdvd
+
+
+Using the pktcdvd debugfs interface
+-----------------------------------
+
+To read pktcdvd device infos in human readable form, do::
+
+	# cat /sys/kernel/debug/pktcdvd/pktcdvd[0-7]/info
+
+For a description of the debugfs interface look into the file:
+
+  Documentation/ABI/testing/debugfs-pktcdvd
+
+
+
+Links
+-----
+
+See http://fy.chalmers.se/~appro/linux/DVD+RW/ for more information
+about DVD writing.