diff options
Diffstat (limited to 'Documentation/video4linux/v4l2-framework.txt')
| -rw-r--r-- | Documentation/video4linux/v4l2-framework.txt | 25 |
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 -------------------- |