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ALSA: firewire-lib: add helper functions to set positions of data channels

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In IEC 61883-6, several types of data are available in AM824 format. The
data is transferred in each data channel. The position of data channel in
data block differs depending on model.

Current implementation has an array to map the index of data channel in an
data block to the position of actual data channel. The implementation
allows each driver to access the mapping directly.

In later commit, the mapping is in specific structure pushed into an
opaque pointer. Helper functions are required.

This commit adds the helper functions for this purpose. In IEC 61883-6,
AM824 format supports many data types, while this specification easily
causes over-engineering. Current AM824 implementation is allowed to handle
two types of data, Multi Bit Linear Audio data (=PCM samples) and MIDI
conformant data (=MIDI messages).

Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
This commit is contained in:
Takashi Sakamoto
2015-09-19 11:21:58 +09:00
committed by Takashi Iwai
parent bc8500da3e
commit f65be911c0
4 changed files with 40 additions and 4 deletions
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5
sound/firewire/dice/dice-stream.c
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@@ -141,8 +141,9 @@ static int start_stream(struct snd_dice *dice, struct amdtp_stream *stream,
pcm_chs /= 2;
for (i = 0; i < pcm_chs; i++) {
stream->pcm_positions[i] = i * 2;
stream->pcm_positions[i + pcm_chs] = i * 2 + 1;
amdtp_am824_set_pcm_position(stream, i, i * 2);
amdtp_am824_set_pcm_position(stream, i + pcm_chs,
i * 2 + 1);
}
}