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1.. SPDX-License-Identifier: GPL-2.02 3Digital TV Common functions4---------------------------5 6DVB devices7~~~~~~~~~~~8 9Those functions are responsible for handling the DVB device nodes.10 11.. kernel-doc:: include/media/dvbdev.h12 13Digital TV Ring buffer14~~~~~~~~~~~~~~~~~~~~~~15 16Those routines implement ring buffers used to handle digital TV data and17copy it from/to userspace.18 19.. note::20 21 1) For performance reasons read and write routines don't check buffer sizes22 and/or number of bytes free/available. This has to be done before these23 routines are called. For example:24 25 .. code-block:: c26 27 /* write @buflen: bytes */28 free = dvb_ringbuffer_free(rbuf);29 if (free >= buflen)30 count = dvb_ringbuffer_write(rbuf, buffer, buflen);31 else32 /* 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 else39 /* do something */40 41 2) If there is exactly one reader and one writer, there is no need42 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.h49 50Digital TV VB2 handler51~~~~~~~~~~~~~~~~~~~~~~52 53.. kernel-doc:: include/media/dvb_vb2.h54