4b83e99ee7
This reverts commit f40eb99897.
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>
3.2 KiB
sysfs interface
The pktcdvd module (packet writing driver) creates the following files in the sysfs: ( 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