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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>
117 lines
3.4 KiB
C
117 lines
3.4 KiB
C
/*
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* AM824 format in Audio and Music Data Transmission Protocol (IEC 61883-6)
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*
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* Copyright (c) 2015 Takashi Sakamoto <o-takashi@sakamocchi.jp>
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*
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* Licensed under the terms of the GNU General Public License, version 2.
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*/
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#include "amdtp-am824.h"
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#define CIP_FMT_AM 0x10
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/* "Clock-based rate control mode" is just supported. */
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#define AMDTP_FDF_AM824 0x00
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/**
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* amdtp_am824_set_parameters - set stream parameters
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* @s: the AMDTP stream to configure
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* @rate: the sample rate
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* @pcm_channels: the number of PCM samples in each data block, to be encoded
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* as AM824 multi-bit linear audio
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* @midi_ports: the number of MIDI ports (i.e., MPX-MIDI Data Channels)
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* @double_pcm_frames: one data block transfers two PCM frames
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*
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* The parameters must be set before the stream is started, and must not be
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* changed while the stream is running.
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*/
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int amdtp_am824_set_parameters(struct amdtp_stream *s, unsigned int rate,
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unsigned int pcm_channels,
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unsigned int midi_ports,
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bool double_pcm_frames)
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{
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int err;
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err = amdtp_stream_set_parameters(s, rate, pcm_channels, midi_ports);
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if (err < 0)
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return err;
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s->fdf = AMDTP_FDF_AM824 | s->sfc;
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/*
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* In IEC 61883-6, one data block represents one event. In ALSA, one
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* event equals to one PCM frame. But Dice has a quirk at higher
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* sampling rate to transfer two PCM frames in one data block.
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*/
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if (double_pcm_frames)
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s->frame_multiplier = 2;
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else
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s->frame_multiplier = 1;
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return 0;
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}
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EXPORT_SYMBOL_GPL(amdtp_am824_set_parameters);
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/**
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* amdtp_am824_set_pcm_position - set an index of data channel for a channel
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* of PCM frame
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* @s: the AMDTP stream
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* @index: the index of data channel in an data block
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* @position: the channel of PCM frame
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*/
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void amdtp_am824_set_pcm_position(struct amdtp_stream *s, unsigned int index,
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unsigned int position)
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{
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if (index < s->pcm_channels)
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s->pcm_positions[index] = position;
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}
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EXPORT_SYMBOL_GPL(amdtp_am824_set_pcm_position);
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/**
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* amdtp_am824_set_midi_position - set a index of data channel for MIDI
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* conformant data channel
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* @s: the AMDTP stream
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* @position: the index of data channel in an data block
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*/
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void amdtp_am824_set_midi_position(struct amdtp_stream *s,
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unsigned int position)
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{
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s->midi_position = position;
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}
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EXPORT_SYMBOL_GPL(amdtp_am824_set_midi_position);
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/**
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* amdtp_am824_add_pcm_hw_constraints - add hw constraints for PCM substream
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* @s: the AMDTP stream for AM824 data block, must be initialized.
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* @runtime: the PCM substream runtime
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*
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*/
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int amdtp_am824_add_pcm_hw_constraints(struct amdtp_stream *s,
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struct snd_pcm_runtime *runtime)
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{
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int err;
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err = amdtp_stream_add_pcm_hw_constraints(s, runtime);
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if (err < 0)
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return err;
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/* AM824 in IEC 61883-6 can deliver 24bit data. */
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return snd_pcm_hw_constraint_msbits(runtime, 0, 32, 24);
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}
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EXPORT_SYMBOL_GPL(amdtp_am824_add_pcm_hw_constraints);
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/**
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* amdtp_am824_init - initialize an AMDTP stream structure to handle AM824
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* data block
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* @s: the AMDTP stream to initialize
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* @unit: the target of the stream
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* @dir: the direction of stream
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* @flags: the packet transmission method to use
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*/
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int amdtp_am824_init(struct amdtp_stream *s, struct fw_unit *unit,
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enum amdtp_stream_direction dir, enum cip_flags flags)
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{
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return amdtp_stream_init(s, unit, dir, flags, CIP_FMT_AM);
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}
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EXPORT_SYMBOL_GPL(amdtp_am824_init);
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