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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-11 08:27:49 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-11 08:27:49 +0000
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Adding upstream version 6.6.15.upstream/6.6.15
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
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+.. SPDX-License-Identifier: GPL-2.0
+
+Digital TV Common functions
+---------------------------
+
+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