Commit 1cea5180 authored by Jens Axboe's avatar Jens Axboe
Browse files

block: remove pktcdvd driver 

This driver has long outlived it's utility, and it's broken and unloved.
The main use case for this was direct mount with UDF of cd-rw drives
that required 32kb packets. It would collect writes into that size and
write them out in multiples of that. That's not a common use case
anymore, the world has moved on from those kinds of media. To make
matters worse, it's actively breaking setups where it's not even
required or useful.

Link: https://lore.kernel.org/linux-block/fxg6dksau4jsk3u5xldlyo2m7qgiux6vtdrz5rywseotsouqdv@urcrwz6qtd3r/
Link: https://lore.kernel.org/linux-block/dcc4836e-6da9-4208-ad27-bbd44b3a2063@kernel.dk/


Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarHannes Reinecke <hare@kernel.org>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 10d77a8c

Documentation/ABI/testing/debugfs-pktcdvd

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What:           /sys/kernel/debug/pktcdvd/pktcdvd[0-7]

Date:           Oct. 2006

KernelVersion:  2.6.20

Contact:        Thomas Maier <balagi@justmail.de>

Description:



The pktcdvd module (packet writing driver) creates

these files in debugfs:



/sys/kernel/debug/pktcdvd/pktcdvd[0-7]/



    ====            ====== ====================================

    info            0444   Lots of driver statistics and infos.

    ====            ====== ====================================



Example::



    cat /sys/kernel/debug/pktcdvd/pktcdvd0/info

Documentation/ABI/testing/sysfs-class-pktcdvd

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sysfs interface

---------------

The pktcdvd module (packet writing driver) creates the following files in the

sysfs: (<devid> is in the format major:minor)



What:		/sys/class/pktcdvd/add

What:		/sys/class/pktcdvd/remove

What:		/sys/class/pktcdvd/device_map

Date:		Oct. 2006

KernelVersion:	2.6.20

Contact:	Thomas Maier <balagi@justmail.de>

Description:



		==========	==============================================

		add		(WO) Write a block device id (major:minor) to

				create a new pktcdvd device and map it to the

				block device.



		remove		(WO) Write the pktcdvd device id (major:minor)

				to remove the pktcdvd device.



		device_map	(RO) Shows the device mapping in format:

				pktcdvd[0-7] <pktdevid> <blkdevid>

		==========	==============================================





What:		/sys/class/pktcdvd/pktcdvd[0-7]/dev

What:		/sys/class/pktcdvd/pktcdvd[0-7]/uevent

Date:		Oct. 2006

KernelVersion:	2.6.20

Contact:	Thomas Maier <balagi@justmail.de>

Description:

		dev:	(RO) Device id



		uevent:	(WO) To send a uevent





What:		/sys/class/pktcdvd/pktcdvd[0-7]/stat/packets_started

What:		/sys/class/pktcdvd/pktcdvd[0-7]/stat/packets_finished

What:		/sys/class/pktcdvd/pktcdvd[0-7]/stat/kb_written

What:		/sys/class/pktcdvd/pktcdvd[0-7]/stat/kb_read

What:		/sys/class/pktcdvd/pktcdvd[0-7]/stat/kb_read_gather

What:		/sys/class/pktcdvd/pktcdvd[0-7]/stat/reset

Date:		Oct. 2006

KernelVersion:	2.6.20

Contact:	Thomas Maier <balagi@justmail.de>

Description:

		packets_started:	(RO) Number of started packets.



		packets_finished:	(RO) Number of finished packets.



		kb_written:		(RO) kBytes written.



		kb_read:		(RO) kBytes read.



		kb_read_gather:		(RO) kBytes read to fill write packets.



		reset:			(WO) Write any value to it to reset

					pktcdvd device statistic values, like

					bytes read/written.





What:		/sys/class/pktcdvd/pktcdvd[0-7]/write_queue/size

What:		/sys/class/pktcdvd/pktcdvd[0-7]/write_queue/congestion_off

What:		/sys/class/pktcdvd/pktcdvd[0-7]/write_queue/congestion_on

Date:		Oct. 2006

KernelVersion:	2.6.20

Contact:	Thomas Maier <balagi@justmail.de>

Description:

		==============	================================================

		size		(RO) Contains the size of the bio write queue.



		congestion_off	(RW) If bio write queue size is below this mark,

				accept new bio requests from the block layer.



		congestion_on	(RW) If bio write queue size is higher as this

				mark, do no longer accept bio write requests

				from the block layer and wait till the pktcdvd

				device has processed enough bio's so that bio

				write queue size is below congestion off mark.

				A value of <= 0 disables congestion control.

		==============	================================================





Example:

--------

To use the pktcdvd sysfs interface directly, you can do::



    # create a new pktcdvd device mapped to /dev/hdc

    echo "22:0" >/sys/class/pktcdvd/add

    cat /sys/class/pktcdvd/device_map

    # assuming device pktcdvd0 was created, look at stat's

    cat /sys/class/pktcdvd/pktcdvd0/stat/kb_written

    # print the device id of the mapped block device

    fgrep pktcdvd0 /sys/class/pktcdvd/device_map

    # remove device, using pktcdvd0 device id   253:0

    echo "253:0" >/sys/class/pktcdvd/remove

Documentation/cdrom/packet-writing.rst

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==============

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.

Documentation/userspace-api/ioctl/ioctl-number.rst

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@@ -220,7 +220,6 @@ Code Seq# Include File Comments 
             include/linux/falloc.h,

             linux/fs.h,

'X'   all    fs/ocfs2/ocfs_fs.h                                      conflict!

'X'   01     linux/pktcdvd.h                                         conflict!

'Z'   14-15  drivers/message/fusion/mptctl.h

'['   00-3F  linux/usb/tmc.h                                         USB Test and Measurement Devices

                                                                     <mailto:gregkh@linuxfoundation.org>

MAINTAINERS

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@@ -19697,13 +19697,6 @@ S: Supported 
F:	Documentation/devicetree/bindings/input/pine64,pinephone-keyboard.yaml

F:	drivers/input/keyboard/pinephone-keyboard.c









PKTCDVD DRIVER









M:	linux-block@vger.kernel.org









S:	Orphan









F:	drivers/block/pktcdvd.c









F:	include/linux/pktcdvd.h









F:	include/uapi/linux/pktcdvd.h

















PLANTOWER PMS7003 AIR POLLUTION SENSOR DRIVER









M:	Tomasz Duszynski <tduszyns@gmail.com>









S:	Maintained