From 849369d6c66d3054688672f97d31fceb8e8230fb Mon Sep 17 00:00:00 2001 From: root Date: Fri, 25 Dec 2015 04:40:36 +0000 Subject: initial_commit --- Documentation/DocBook/v4l/vidioc-g-priority.xml | 144 ++++++++++++++++++++++++ 1 file changed, 144 insertions(+) create mode 100644 Documentation/DocBook/v4l/vidioc-g-priority.xml (limited to 'Documentation/DocBook/v4l/vidioc-g-priority.xml') diff --git a/Documentation/DocBook/v4l/vidioc-g-priority.xml b/Documentation/DocBook/v4l/vidioc-g-priority.xml new file mode 100644 index 00000000..5fb00197 --- /dev/null +++ b/Documentation/DocBook/v4l/vidioc-g-priority.xml @@ -0,0 +1,144 @@ + + + ioctl VIDIOC_G_PRIORITY, VIDIOC_S_PRIORITY + &manvol; + + + + VIDIOC_G_PRIORITY + VIDIOC_S_PRIORITY + Query or request the access priority associated with a +file descriptor + + + + + + int ioctl + int fd + int request + enum v4l2_priority *argp + + + + + int ioctl + int fd + int request + const enum v4l2_priority *argp + + + + + + Arguments + + + + fd + + &fd; + + + + request + + VIDIOC_G_PRIORITY, VIDIOC_S_PRIORITY + + + + argp + + Pointer to an enum v4l2_priority type. + + + + + + + Description + + To query the current access priority +applications call the VIDIOC_G_PRIORITY ioctl +with a pointer to an enum v4l2_priority variable where the driver stores +the current priority. + + To request an access priority applications store the +desired priority in an enum v4l2_priority variable and call +VIDIOC_S_PRIORITY ioctl with a pointer to this +variable. + + + enum v4l2_priority + + &cs-def; + + + V4L2_PRIORITY_UNSET + 0 + + + + V4L2_PRIORITY_BACKGROUND + 1 + Lowest priority, usually applications running in +background, for example monitoring VBI transmissions. A proxy +application running in user space will be necessary if multiple +applications want to read from a device at this priority. + + + V4L2_PRIORITY_INTERACTIVE + 2 + + + + V4L2_PRIORITY_DEFAULT + 2 + Medium priority, usually applications started and +interactively controlled by the user. For example TV viewers, Teletext +browsers, or just "panel" applications to change the channel or video +controls. This is the default priority unless an application requests +another. + + + V4L2_PRIORITY_RECORD + 3 + Highest priority. Only one file descriptor can have +this priority, it blocks any other fd from changing device properties. +Usually applications which must not be interrupted, like video +recording. + + + +
+ + + + &return-value; + + + + EINVAL + + The requested priority value is invalid, or the +driver does not support access priorities. + + + + EBUSY + + Another application already requested higher +priority. + + + + + + + -- cgit v1.2.3