diff options
Diffstat (limited to 'Documentation/userspace-api/media/v4l/dev-raw-vbi.rst')
| -rw-r--r-- | Documentation/userspace-api/media/v4l/dev-raw-vbi.rst | 19 |
1 files changed, 6 insertions, 13 deletions
diff --git a/Documentation/userspace-api/media/v4l/dev-raw-vbi.rst b/Documentation/userspace-api/media/v4l/dev-raw-vbi.rst index bb52f85a619c..3f43a01ba938 100644 --- a/Documentation/userspace-api/media/v4l/dev-raw-vbi.rst +++ b/Documentation/userspace-api/media/v4l/dev-raw-vbi.rst @@ -1,4 +1,5 @@ .. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later +.. c:namespace:: V4L .. _raw-vbi: @@ -32,7 +33,6 @@ applications must call the :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctl. Accessed as ``/dev/vbi``, raw VBI capturing or output is the default device function. - Querying Capabilities ===================== @@ -44,7 +44,6 @@ in the ``capabilities`` field of struct read/write, streaming or asynchronous I/O methods must be supported. VBI devices may or may not have a tuner or modulator. - Supplemental Functions ====================== @@ -53,7 +52,6 @@ VBI devices shall support :ref:`video input or output <video>`, ioctls as needed. The :ref:`video standard <standard>` ioctls provide information vital to program a VBI device, therefore must be supported. - Raw VBI Format Negotiation ========================== @@ -62,7 +60,7 @@ frequency. To properly interpret the data V4L2 specifies an ioctl to query the sampling parameters. Moreover, to allow for some flexibility applications can also suggest different parameters. -As usual these parameters are *not* reset at :ref:`open() <func-open>` +As usual these parameters are *not* reset at :c:func:`open()` time to permit Unix tool chains, programming a device and then reading from it as if it was a plain file. Well written V4L2 applications should always ensure they really get what they want, requesting reasonable @@ -91,8 +89,8 @@ happen for instance when the video and VBI areas to capture would overlap, or when the driver supports multiple opens and another process already requested VBI capturing or output. Anyway, applications must expect other resource allocation points which may return ``EBUSY``, at the -:ref:`VIDIOC_STREAMON` ioctl and the first :ref:`read() <func-read>` -, :ref:`write() <func-write>` and :ref:`select() <func-select>` calls. +:ref:`VIDIOC_STREAMON` ioctl and the first :c:func:`read()` +, :c:func:`write()` and :c:func:`select()` calls. VBI devices must implement both the :ref:`VIDIOC_G_FMT <VIDIOC_G_FMT>` and :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctl, even if :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ignores all requests @@ -182,7 +180,6 @@ and always returns default parameters as :ref:`VIDIOC_G_FMT <VIDIOC_G_FMT>` does - This array is reserved for future extensions. Drivers and applications must set it to zero. - .. tabularcolumns:: |p{4.4cm}|p{1.5cm}|p{11.6cm}| .. _vbifmt-flags: @@ -218,7 +215,6 @@ and always returns default parameters as :ref:`VIDIOC_G_FMT <VIDIOC_G_FMT>` does non-zero. - .. _vbi-hsync: .. kernel-figure:: vbi_hsync.svg @@ -227,7 +223,6 @@ and always returns default parameters as :ref:`VIDIOC_G_FMT <VIDIOC_G_FMT>` does **Figure 4.1. Line synchronization** - .. _vbi-525: .. kernel-figure:: vbi_525.svg @@ -251,7 +246,6 @@ negotiation, or after switching the video standard which may invalidate the negotiated VBI parameters, should be refused by the driver. A format change during active I/O is not permitted. - Reading and writing VBI images ============================== @@ -261,7 +255,6 @@ consisting of two fields of VBI images immediately following in memory. The total size of a frame computes as follows: - .. code-block:: c (count[0] + count[1]) * samples_per_line * sample size in bytes @@ -276,8 +269,8 @@ The latter bears the possibility of synchronizing video and VBI data by using buffer timestamps. Remember the :ref:`VIDIOC_STREAMON <VIDIOC_STREAMON>` ioctl and the -first :ref:`read() <func-read>`, :ref:`write() <func-write>` and -:ref:`select() <func-select>` call can be resource allocation +first :c:func:`read()`, :c:func:`write()` and +:c:func:`select()` call can be resource allocation points returning an ``EBUSY`` error code if the required hardware resources are temporarily unavailable, for example the device is already in use by another process. |