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authorHans Verkuil <hans.verkuil@cisco.com>2014-12-01 10:10:45 -0300
committerMauro Carvalho Chehab <mchehab@osg.samsung.com>2014-12-23 10:32:52 -0200
commit88f414f476bdf9def8123fec49890a3c94b5fb53 (patch)
treeef5f4ff015c2c169850a38ac22f515bd4e60fcdc /Documentation/video4linux
parent17028cdb74bf8bb593aebe5550bc90325fa9af88 (diff)
downloadkernel-88f414f476bdf9def8123fec49890a3c94b5fb53.tar.gz
[media] v4l2-framework.txt: document debug attribute
The debug attribute in /sys/class/video4linux/<devX>/debug was never documented. Add this. Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com> Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com> Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
Diffstat (limited to 'Documentation/video4linux')
-rw-r--r--Documentation/video4linux/v4l2-framework.txt25
1 files changed, 23 insertions, 2 deletions
diff --git a/Documentation/video4linux/v4l2-framework.txt b/Documentation/video4linux/v4l2-framework.txt
index a11dff07ef71..f586e29ce221 100644
--- a/Documentation/video4linux/v4l2-framework.txt
+++ b/Documentation/video4linux/v4l2-framework.txt
@@ -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
--------------------