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