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56 lines
1.6 KiB
ReStructuredText
56 lines
1.6 KiB
ReStructuredText
Digital TV Common functions
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---------------------------
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Math functions
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~~~~~~~~~~~~~~
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Provide some commonly-used math functions, usually required in order to
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estimate signal strength and signal to noise measurements in dB.
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.. kernel-doc:: drivers/media/dvb-core/dvb_math.h
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DVB devices
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~~~~~~~~~~~
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Those functions are responsible for handling the DVB device nodes.
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.. kernel-doc:: drivers/media/dvb-core/dvbdev.h
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Digital TV Ring buffer
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~~~~~~~~~~~~~~~~~~~~~~
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Those routines implement ring buffers used to handle digital TV data and
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copy it from/to userspace.
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.. note::
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1) For performance reasons read and write routines don't check buffer sizes
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and/or number of bytes free/available. This has to be done before these
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routines are called. For example:
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.. code-block:: c
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/* write @buflen: bytes */
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free = dvb_ringbuffer_free(rbuf);
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if (free >= buflen)
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count = dvb_ringbuffer_write(rbuf, buffer, buflen);
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else
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/* do something */
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/* read min. 1000, max. @bufsize: bytes */
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avail = dvb_ringbuffer_avail(rbuf);
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if (avail >= 1000)
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count = dvb_ringbuffer_read(rbuf, buffer, min(avail, bufsize));
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else
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/* do something */
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2) If there is exactly one reader and one writer, there is no need
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to lock read or write operations.
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Two or more readers must be locked against each other.
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Flushing the buffer counts as a read operation.
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Resetting the buffer counts as a read and write operation.
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Two or more writers must be locked against each other.
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.. kernel-doc:: drivers/media/dvb-core/dvb_ringbuffer.h
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