From 5d1646d90e1f2cceb9f0828f4b28318cd0ec7744 Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Sat, 27 Apr 2024 12:05:51 +0200 Subject: Adding upstream version 5.10.209. Signed-off-by: Daniel Baumann --- Documentation/driver-api/media/dtv-common.rst | 62 +++++++++++++++++++++++++++ 1 file changed, 62 insertions(+) create mode 100644 Documentation/driver-api/media/dtv-common.rst (limited to 'Documentation/driver-api/media/dtv-common.rst') diff --git a/Documentation/driver-api/media/dtv-common.rst b/Documentation/driver-api/media/dtv-common.rst new file mode 100644 index 000000000..f8b2c4dc8 --- /dev/null +++ b/Documentation/driver-api/media/dtv-common.rst @@ -0,0 +1,62 @@ +.. 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 -- cgit v1.2.3