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Diffstat (limited to 'Documentation/cdrom')
| -rw-r--r-- | Documentation/cdrom/cdrom-standard.rst | 1047 | ||||
| -rw-r--r-- | Documentation/cdrom/ide-cd.rst | 538 | ||||
| -rw-r--r-- | Documentation/cdrom/index.rst | 19 | ||||
| -rw-r--r-- | Documentation/cdrom/packet-writing.rst | 139 |
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diff --git a/Documentation/cdrom/cdrom-standard.rst b/Documentation/cdrom/cdrom-standard.rst new file mode 100644 index 000000000..70500b189 --- /dev/null +++ b/Documentation/cdrom/cdrom-standard.rst @@ -0,0 +1,1047 @@ +======================= +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. |