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authorJens Axboe <axboe@kernel.dk>2023-01-05 00:44:13 +0300
committerJens Axboe <axboe@kernel.dk>2023-01-05 00:44:13 +0300
commit4b83e99ee7092df37a5cf292fde976ebc475ea63 (patch)
treeb7f05be90b358604d23525fc3c00b7b91f7064d3 /Documentation/ABI/testing/sysfs-class-pktcdvd
parent050a4f341f35bf51db321c7f68700f9e0b1a7552 (diff)
downloadlinux-4b83e99ee7092df37a5cf292fde976ebc475ea63.tar.xz
Revert "pktcdvd: remove driver."
This reverts commit f40eb99897af665f11858dd7b56edcb62c3f3c67. There are apparently still users out there of this driver. While we'd love to remove it to ease the maintenance burden, let's reinstate it for now until better (userspace) solutions can be developed. Link: https://lore.kernel.org/lkml/20230104190115.ceglfefco475ev6c@pali/ Reported-by: Pali Rohár <pali@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
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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