![Mauro Carvalho Chehab](/assets/img/avatar_default.png)
All Documentation files outside the uAPI are all licensed with, at least, GPL 2.0. So, mark them as such. The ondes at media/uapi are at least GFDL 1.1+. Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
63 lines
1.7 KiB
ReStructuredText
63 lines
1.7 KiB
ReStructuredText
.. SPDX-License-Identifier: GPL-2.0
|
|
|
|
Digital TV Common functions
|
|
---------------------------
|
|
|
|
Math functions
|
|
~~~~~~~~~~~~~~
|
|
|
|
Provide some commonly-used math functions, usually required in order to
|
|
estimate signal strength and signal to noise measurements in dB.
|
|
|
|
.. kernel-doc:: include/media/dvb_math.h
|
|
|
|
|
|
DVB devices
|
|
~~~~~~~~~~~
|
|
|
|
Those functions are responsible for handling the DVB device nodes.
|
|
|
|
.. kernel-doc:: include/media/dvbdev.h
|
|
|
|
Digital TV Ring buffer
|
|
~~~~~~~~~~~~~~~~~~~~~~
|
|
|
|
Those routines implement ring buffers used to handle digital TV data and
|
|
copy it from/to userspace.
|
|
|
|
.. note::
|
|
|
|
1) For performance reasons read and write routines don't check buffer sizes
|
|
and/or number of bytes free/available. This has to be done before these
|
|
routines are called. For example:
|
|
|
|
.. code-block:: c
|
|
|
|
/* write @buflen: bytes */
|
|
free = dvb_ringbuffer_free(rbuf);
|
|
if (free >= buflen)
|
|
count = dvb_ringbuffer_write(rbuf, buffer, buflen);
|
|
else
|
|
/* do something */
|
|
|
|
/* read min. 1000, max. @bufsize: bytes */
|
|
avail = dvb_ringbuffer_avail(rbuf);
|
|
if (avail >= 1000)
|
|
count = dvb_ringbuffer_read(rbuf, buffer, min(avail, bufsize));
|
|
else
|
|
/* do something */
|
|
|
|
2) If there is exactly one reader and one writer, there is no need
|
|
to lock read or write operations.
|
|
Two or more readers must be locked against each other.
|
|
Flushing the buffer counts as a read operation.
|
|
Resetting the buffer counts as a read and write operation.
|
|
Two or more writers must be locked against each other.
|
|
|
|
.. kernel-doc:: include/media/dvb_ringbuffer.h
|
|
|
|
Digital TV VB2 handler
|
|
~~~~~~~~~~~~~~~~~~~~~~
|
|
|
|
.. kernel-doc:: include/media/dvb_vb2.h
|