diff options
Diffstat (limited to 'Documentation/DocBook/media/v4l/common.xml')
| -rw-r--r-- | Documentation/DocBook/media/v4l/common.xml | 89 |
1 files changed, 35 insertions, 54 deletions
diff --git a/Documentation/DocBook/media/v4l/common.xml b/Documentation/DocBook/media/v4l/common.xml index 1ddf354aa997..5a97935e75a1 100644 --- a/Documentation/DocBook/media/v4l/common.xml +++ b/Documentation/DocBook/media/v4l/common.xml @@ -240,15 +240,15 @@ methods</link> supported by the device.</para> <para>Starting with kernel version 3.1, VIDIOC-QUERYCAP will return the V4L2 API version used by the driver, with generally matches the Kernel version. -There's no need of using &VIDIOC-QUERYCAP; to check if an specific ioctl is -supported, the V4L2 core now returns ENOIOCTLCMD if a driver doesn't provide +There's no need of using &VIDIOC-QUERYCAP; to check if a specific ioctl is +supported, the V4L2 core now returns ENOTTY if a driver doesn't provide support for an ioctl.</para> <para>Other features can be queried by calling the respective ioctl, for example &VIDIOC-ENUMINPUT; to learn about the number, types and names of video connectors on the device. Although abstraction is a major objective of this API, the -ioctl also allows driver specific applications to reliable identify +&VIDIOC-QUERYCAP; ioctl also allows driver specific applications to reliably identify the driver.</para> <para>All V4L2 drivers must support @@ -278,9 +278,7 @@ Applications requiring a different priority will usually call the &VIDIOC-QUERYCAP; ioctl.</para> <para>Ioctls changing driver properties, such as &VIDIOC-S-INPUT;, -return an &EBUSY; after another application obtained higher priority. -An event mechanism to notify applications about asynchronous property -changes has been proposed but not added yet.</para> +return an &EBUSY; after another application obtained higher priority.</para> </section> <section id="video"> @@ -288,9 +286,9 @@ changes has been proposed but not added yet.</para> <para>Video inputs and outputs are physical connectors of a device. These can be for example RF connectors (antenna/cable), CVBS -a.k.a. Composite Video, S-Video or RGB connectors. Only video and VBI -capture devices have inputs, output devices have outputs, at least one -each. Radio devices have no video inputs or outputs.</para> +a.k.a. Composite Video, S-Video or RGB connectors. Video and VBI +capture devices have inputs. Video and VBI output devices have outputs, +at least one each. Radio devices have no video inputs or outputs.</para> <para>To learn about the number and attributes of the available inputs and outputs applications can enumerate them with the @@ -299,30 +297,13 @@ available inputs and outputs applications can enumerate them with the ioctl also contains signal status information applicable when the current video input is queried.</para> - <para>The &VIDIOC-G-INPUT; and &VIDIOC-G-OUTPUT; ioctl return the + <para>The &VIDIOC-G-INPUT; and &VIDIOC-G-OUTPUT; ioctls return the index of the current video input or output. To select a different input or output applications call the &VIDIOC-S-INPUT; and -&VIDIOC-S-OUTPUT; ioctl. Drivers must implement all the input ioctls +&VIDIOC-S-OUTPUT; ioctls. Drivers must implement all the input ioctls when the device has one or more inputs, all the output ioctls when the device has one or more outputs.</para> - <!-- - <figure id=io-tree> - <title>Input and output enumeration is the root of most device properties.</title> - <mediaobject> - <imageobject> - <imagedata fileref="links.pdf" format="ps" /> - </imageobject> - <imageobject> - <imagedata fileref="links.gif" format="gif" /> - </imageobject> - <textobject> - <phrase>Links between various device property structures.</phrase> - </textobject> - </mediaobject> - </figure> - --> - <example> <title>Information about the current video input</title> @@ -330,20 +311,20 @@ device has one or more outputs.</para> &v4l2-input; input; int index; -if (-1 == ioctl (fd, &VIDIOC-G-INPUT;, &index)) { - perror ("VIDIOC_G_INPUT"); - exit (EXIT_FAILURE); +if (-1 == ioctl(fd, &VIDIOC-G-INPUT;, &index)) { + perror("VIDIOC_G_INPUT"); + exit(EXIT_FAILURE); } -memset (&input, 0, sizeof (input)); +memset(&input, 0, sizeof(input)); input.index = index; -if (-1 == ioctl (fd, &VIDIOC-ENUMINPUT;, &input)) { - perror ("VIDIOC_ENUMINPUT"); - exit (EXIT_FAILURE); +if (-1 == ioctl(fd, &VIDIOC-ENUMINPUT;, &input)) { + perror("VIDIOC_ENUMINPUT"); + exit(EXIT_FAILURE); } -printf ("Current input: %s\n", input.name); +printf("Current input: %s\n", input.name); </programlisting> </example> @@ -355,9 +336,9 @@ int index; index = 0; -if (-1 == ioctl (fd, &VIDIOC-S-INPUT;, &index)) { - perror ("VIDIOC_S_INPUT"); - exit (EXIT_FAILURE); +if (-1 == ioctl(fd, &VIDIOC-S-INPUT;, &index)) { + perror("VIDIOC_S_INPUT"); + exit(EXIT_FAILURE); } </programlisting> </example> @@ -397,7 +378,7 @@ available inputs and outputs applications can enumerate them with the also contains signal status information applicable when the current audio input is queried.</para> - <para>The &VIDIOC-G-AUDIO; and &VIDIOC-G-AUDOUT; ioctl report + <para>The &VIDIOC-G-AUDIO; and &VIDIOC-G-AUDOUT; ioctls report the current audio input and output, respectively. Note that, unlike &VIDIOC-G-INPUT; and &VIDIOC-G-OUTPUT; these ioctls return a structure as <constant>VIDIOC_ENUMAUDIO</constant> and @@ -408,11 +389,11 @@ applications call the &VIDIOC-S-AUDIO; ioctl. To select an audio output (which presently has no changeable properties) applications call the &VIDIOC-S-AUDOUT; ioctl.</para> - <para>Drivers must implement all input ioctls when the device -has one or more inputs, all output ioctls when the device has one -or more outputs. When the device has any audio inputs or outputs the -driver must set the <constant>V4L2_CAP_AUDIO</constant> flag in the -&v4l2-capability; returned by the &VIDIOC-QUERYCAP; ioctl.</para> + <para>Drivers must implement all audio input ioctls when the device +has multiple selectable audio inputs, all audio output ioctls when the +device has multiple selectable audio outputs. When the device has any +audio inputs or outputs the driver must set the <constant>V4L2_CAP_AUDIO</constant> +flag in the &v4l2-capability; returned by the &VIDIOC-QUERYCAP; ioctl.</para> <example> <title>Information about the current audio input</title> @@ -420,14 +401,14 @@ driver must set the <constant>V4L2_CAP_AUDIO</constant> flag in the <programlisting> &v4l2-audio; audio; -memset (&audio, 0, sizeof (audio)); +memset(&audio, 0, sizeof(audio)); -if (-1 == ioctl (fd, &VIDIOC-G-AUDIO;, &audio)) { - perror ("VIDIOC_G_AUDIO"); - exit (EXIT_FAILURE); +if (-1 == ioctl(fd, &VIDIOC-G-AUDIO;, &audio)) { + perror("VIDIOC_G_AUDIO"); + exit(EXIT_FAILURE); } -printf ("Current input: %s\n", audio.name); +printf("Current input: %s\n", audio.name); </programlisting> </example> @@ -437,13 +418,13 @@ printf ("Current input: %s\n", audio.name); <programlisting> &v4l2-audio; audio; -memset (&audio, 0, sizeof (audio)); /* clear audio.mode, audio.reserved */ +memset(&audio, 0, sizeof(audio)); /* clear audio.mode, audio.reserved */ audio.index = 0; -if (-1 == ioctl (fd, &VIDIOC-S-AUDIO;, &audio)) { - perror ("VIDIOC_S_AUDIO"); - exit (EXIT_FAILURE); +if (-1 == ioctl(fd, &VIDIOC-S-AUDIO;, &audio)) { + perror("VIDIOC_S_AUDIO"); + exit(EXIT_FAILURE); } </programlisting> </example> |