| .. 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 |
