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Open Menu /Documentation/ABI/testing/sysfs-class-pktcdvd 
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What:           /sys/class/pktcdvd/
Date:           Oct. 2006
KernelVersion:  2.6.20
Contact:        Thomas Maier <balagi@justmail.de>
Description:

sysfs interface
---------------

The pktcdvd module (packet writing driver) creates
these files in the sysfs:
(<devid> is in format  major:minor )

/sys/class/pktcdvd/
    add            (0200)  Write a block device id (major:minor)
                           to create a new pktcdvd device and map
                           it to the block device.

    remove         (0200)  Write the pktcdvd device id (major:minor)
                           to it to remove the pktcdvd device.

    device_map     (0444)  Shows the device mapping in format:
                             pktcdvd[0-7] <pktdevid> <blkdevid>

/sys/class/pktcdvd/pktcdvd[0-7]/
    dev                   (0444) Device id
    uevent                (0200) To send an uevent.

/sys/class/pktcdvd/pktcdvd[0-7]/stat/
    packets_started       (0444) Number of started packets.
    packets_finished      (0444) Number of finished packets.

    kb_written            (0444) kBytes written.
    kb_read               (0444) kBytes read.
    kb_read_gather        (0444) kBytes read to fill write packets.

    reset                 (0200) Write any value to it to reset
                                 pktcdvd device statistic values, like
                                 bytes read/written.

/sys/class/pktcdvd/pktcdvd[0-7]/write_queue/
    size                  (0444) Contains the size of the bio write
                                 queue.

    congestion_off        (0644) If bio write queue size is below
                                 this mark, accept new bio requests
                                 from the block layer.

    congestion_on         (0644) 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