1.. SPDX-License-Identifier: GPL-2.0
2
3Digital TV Common functions
4---------------------------
5
6Math functions
7~~~~~~~~~~~~~~
8
9Provide some commonly-used math functions, usually required in order to
10estimate signal strength and signal to noise measurements in dB.
11
12.. kernel-doc:: include/media/dvb_math.h
13
14
15DVB devices
16~~~~~~~~~~~
17
18Those functions are responsible for handling the DVB device nodes.
19
20.. kernel-doc:: include/media/dvbdev.h
21
22Digital TV Ring buffer
23~~~~~~~~~~~~~~~~~~~~~~
24
25Those routines implement ring buffers used to handle digital TV data and
26copy it from/to userspace.
27
28.. note::
29
30  1) For performance reasons read and write routines don't check buffer sizes
31     and/or number of bytes free/available. This has to be done before these
32     routines are called. For example:
33
34   .. code-block:: c
35
36        /* write @buflen: bytes */
37        free = dvb_ringbuffer_free(rbuf);
38        if (free >= buflen)
39                count = dvb_ringbuffer_write(rbuf, buffer, buflen);
40        else
41                /* do something */
42
43        /* read min. 1000, max. @bufsize: bytes */
44        avail = dvb_ringbuffer_avail(rbuf);
45        if (avail >= 1000)
46                count = dvb_ringbuffer_read(rbuf, buffer, min(avail, bufsize));
47        else
48                /* do something */
49
50  2) If there is exactly one reader and one writer, there is no need
51     to lock read or write operations.
52     Two or more readers must be locked against each other.
53     Flushing the buffer counts as a read operation.
54     Resetting the buffer counts as a read and write operation.
55     Two or more writers must be locked against each other.
56
57.. kernel-doc:: include/media/dvb_ringbuffer.h
58
59Digital TV VB2 handler
60~~~~~~~~~~~~~~~~~~~~~~
61
62.. kernel-doc:: include/media/dvb_vb2.h
63