linux-imx

// SPDX-License-Identifier: GPL-2.0-only

/*

 * AM824 format in Audio and Music Data Transmission Protocol (IEC 61883-6)

 *

 * Copyright (c) Clemens Ladisch <clemens@ladisch.de>

 * Copyright (c) 2015 Takashi Sakamoto <o-takashi@sakamocchi.jp>

 */

​

#include <linux/slab.h>

​

#include "amdtp-am824.h"

​

#define CIP_FMT_AM      0x10

​

/* "Clock-based rate control mode" is just supported. */

#define AMDTP_FDF_AM824     0x00

​

/*

 * Nominally 3125 bytes/second, but the MIDI port's clock might be

 * 1% too slow, and the bus clock 100 ppm too fast.

 */

#define MIDI_BYTES_PER_SECOND   3093

​

/*

 * Several devices look only at the first eight data blocks.

 * In any case, this is more than enough for the MIDI data rate.

 */

#define MAX_MIDI_RX_BLOCKS  8

​

struct amdtp_am824 {

    struct snd_rawmidi_substream *midi[AM824_MAX_CHANNELS_FOR_MIDI * 8];

    int midi_fifo_limit;

    int midi_fifo_used[AM824_MAX_CHANNELS_FOR_MIDI * 8];

    unsigned int pcm_channels;

    unsigned int midi_ports;

​

    u8 pcm_positions[AM824_MAX_CHANNELS_FOR_PCM];

    u8 midi_position;

​

    unsigned int frame_multiplier;

};

​

/**

 * amdtp_am824_set_parameters - set stream parameters

 * @s: the AMDTP stream to configure

 * @rate: the sample rate

 * @pcm_channels: the number of PCM samples in each data block, to be encoded

 *                as AM824 multi-bit linear audio

 * @midi_ports: the number of MIDI ports (i.e., MPX-MIDI Data Channels)

 * @double_pcm_frames: one data block transfers two PCM frames

 *

 * The parameters must be set before the stream is started, and must not be

 * changed while the stream is running.

 */

int amdtp_am824_set_parameters(struct amdtp_stream *s, unsigned int rate,

                   unsigned int pcm_channels,

                   unsigned int midi_ports,

                   bool double_pcm_frames)

{

    struct amdtp_am824 *p = s->protocol;

    unsigned int midi_channels;

    unsigned int i;

    int err;