85 lines
3.1 KiB
C
85 lines
3.1 KiB
C
/* -*- c-basic-offset: 8 -*- */
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#ifndef __AMDTP_H
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#define __AMDTP_H
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#include <asm/types.h>
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#include "ieee1394-ioctl.h"
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/* The userspace interface for the Audio & Music Data Transmission
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* Protocol driver is really simple. First, open /dev/amdtp, use the
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* ioctl to configure format, rate, dimension and either plug or
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* channel, then start writing samples.
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*
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* The formats supported by the driver are listed below.
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* AMDTP_FORMAT_RAW corresponds to the AM824 raw format, which can
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* carry any number of channels, so use this if you're streaming
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* multichannel audio. The AMDTP_FORMAT_IEC958_PCM corresponds to the
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* AM824 IEC958 encapsulation without the IEC958 data bit set, using
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* AMDTP_FORMAT_IEC958_AC3 will transmit the samples with the data bit
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* set, suitable for transmitting compressed AC-3 audio.
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*
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* The rate field specifies the transmission rate; supported values
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* are 32000, 44100, 48000, 88200, 96000, 176400 and 192000.
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*
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* The dimension field specifies the dimension of the signal, that is,
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* the number of audio channels. Only AMDTP_FORMAT_RAW supports
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* settings greater than 2.
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*
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* The mode field specifies which transmission mode to use. The AMDTP
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* specifies two different transmission modes: blocking and
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* non-blocking. The blocking transmission mode always send a fixed
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* number of samples, typically 8, 16 or 32. To exactly match the
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* transmission rate, the driver alternates between sending empty and
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* non-empty packets. In non-blocking mode, the driver transmits as
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* small packets as possible. For example, for a transmission rate of
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* 44100Hz, the driver should send 5 41/80 samples in every cycle, but
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* this is not possible so instead the driver alternates between
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* sending 5 and 6 samples.
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*
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* The last thing to specify is either the isochronous channel to use
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* or the output plug to connect to. If you know what channel the
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* destination device will listen on, you can specify the channel
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* directly and use the AMDTP_IOC_CHANNEL ioctl. However, if the
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* destination device chooses the channel and uses the IEC61883-1 plug
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* mechanism, you can specify an output plug to connect to. The
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* driver will pick up the channel number from the plug once the
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* destination device locks the output plug control register. In this
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* case set the plug field and use the AMDTP_IOC_PLUG ioctl.
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*
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* Having configured the interface, the driver now accepts writes of
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* regular 16 bit signed little endian samples, with the channels
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* interleaved. For example, 4 channels would look like:
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*
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* | sample 0 | sample 1 ...
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* | ch. 0 | ch. 1 | ch. 2 | ch. 3 | ch. 0 | ...
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* | lsb | msb | lsb | msb | lsb | msb | lsb | msb | lsb | msb | ...
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*
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*/
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enum {
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AMDTP_FORMAT_RAW,
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AMDTP_FORMAT_IEC958_PCM,
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AMDTP_FORMAT_IEC958_AC3
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};
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enum {
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AMDTP_MODE_BLOCKING,
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AMDTP_MODE_NON_BLOCKING,
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};
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enum {
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AMDTP_INPUT_LE16,
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AMDTP_INPUT_BE16,
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};
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struct amdtp_ioctl {
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__u32 format;
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__u32 rate;
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__u32 dimension;
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__u32 mode;
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union { __u32 channel; __u32 plug; } u;
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};
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#endif /* __AMDTP_H */
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