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Commit 88f414f4 authored by Hans Verkuil's avatar Hans Verkuil Committed by Mauro Carvalho Chehab
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[media] v4l2-framework.txt: document debug attribute 



The debug attribute in /sys/class/video4linux/<devX>/debug was never
documented. Add this.

Signed-off-by: default avatarHans Verkuil <hans.verkuil@cisco.com>
Acked-by: default avatarSakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: default avatarMauro Carvalho Chehab <mchehab@osg.samsung.com>
parent 17028cdb

Documentation/video4linux/v4l2-framework.txt

+23 −2
Original line number Diff line number Diff line
@@ -793,8 +793,10 @@ video_register_device_no_warn() instead. 


Whenever a device node is created some attributes are also created for you.

If you look in /sys/class/video4linux you see the devices. Go into e.g.

video0 and you will see 'name' and 'index' attributes. The 'name' attribute

is the 'name' field of the video_device struct.

video0 and you will see 'name', 'debug' and 'index' attributes. The 'name'

attribute is the 'name' field of the video_device struct. The 'debug' attribute

can be used to enable core debugging. See the next section for more detailed

information on this.



The 'index' attribute is the index of the device node: for each call to

video_register_device() the index is just increased by 1. The first video
@@ -816,6 +818,25 @@ video_device was embedded in it. The vdev->release() callback will never 
be called if the registration failed, nor should you ever attempt to

unregister the device if the registration failed.



video device debugging

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



The 'debug' attribute that is created for each video, vbi, radio or swradio

device in /sys/class/video4linux/<devX>/ allows you to enable logging of

file operations.



It is a bitmask and the following bits can be set:



0x01: Log the ioctl name and error code. VIDIOC_(D)QBUF ioctls are only logged

      if bit 0x08 is also set.

0x02: Log the ioctl name arguments and error code. VIDIOC_(D)QBUF ioctls are

      only logged if bit 0x08 is also set.

0x04: Log the file operations open, release, read, write, mmap and

      get_unmapped_area. The read and write operations are only logged if

      bit 0x08 is also set.

0x08: Log the read and write file operations and the VIDIOC_QBUF and

      VIDIOC_DQBUF ioctls.

0x10: Log the poll file operation.



video_device cleanup

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