xref: /linux/Documentation/ABI/testing/sysfs-class-pktcdvd (revision 48c871c1f6a7c7044dd76774fb469e65c7e2e4e8) 
1What:           /sys/class/pktcdvd/
2Date:           Oct. 2006
3KernelVersion:  2.6.20
4Contact:        Thomas Maier <balagi@justmail.de>
5Description:
6
7sysfs interface
8---------------
9
10The pktcdvd module (packet writing driver) creates
11these files in the sysfs:
12(<devid> is in format  major:minor )
13
14/sys/class/pktcdvd/
15    add            (0200)  Write a block device id (major:minor)
16                           to create a new pktcdvd device and map
17                           it to the block device.
18
19    remove         (0200)  Write the pktcdvd device id (major:minor)
20                           to it to remove the pktcdvd device.
21
22    device_map     (0444)  Shows the device mapping in format:
23                             pktcdvd[0-7] <pktdevid> <blkdevid>
24
25/sys/class/pktcdvd/pktcdvd[0-7]/
26    dev                   (0444) Device id
27    uevent                (0200) To send an uevent.
28
29/sys/class/pktcdvd/pktcdvd[0-7]/stat/
30    packets_started       (0444) Number of started packets.
31    packets_finished      (0444) Number of finished packets.
32
33    kb_written            (0444) kBytes written.
34    kb_read               (0444) kBytes read.
35    kb_read_gather        (0444) kBytes read to fill write packets.
36
37    reset                 (0200) Write any value to it to reset
38                                 pktcdvd device statistic values, like
39                                 bytes read/written.
40
41/sys/class/pktcdvd/pktcdvd[0-7]/write_queue/
42    size                  (0444) Contains the size of the bio write
43                                 queue.
44
45    congestion_off        (0644) If bio write queue size is below
46                                 this mark, accept new bio requests
47                                 from the block layer.
48
49    congestion_on         (0644) If bio write queue size is higher
50                                 as this mark, do no longer accept
51                                 bio write requests from the block
52                                 layer and wait till the pktcdvd
53                                 device has processed enough bio's
54                                 so that bio write queue size is
55                                 below congestion off mark.
56                                 A value of <= 0 disables congestion
57                                 control.
58
59
60Example:
61--------
62To use the pktcdvd sysfs interface directly, you can do:
63
64# create a new pktcdvd device mapped to /dev/hdc
65echo "22:0" >/sys/class/pktcdvd/add
66cat /sys/class/pktcdvd/device_map
67# assuming device pktcdvd0 was created, look at stat's
68cat /sys/class/pktcdvd/pktcdvd0/stat/kb_written
69# print the device id of the mapped block device
70fgrep pktcdvd0 /sys/class/pktcdvd/device_map
71# remove device, using pktcdvd0 device id   253:0
72echo "253:0" >/sys/class/pktcdvd/remove
73