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diff --git a/Documentation/cdrom/packet-writing.rst b/Documentation/cdrom/packet-writing.rst new file mode 100644 index 000000000..43db58c50 --- /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 https://github.com/pali/udftools + +- 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/linux/software/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. |