pcm.c

/* pcm.c
**
** Copyright 2011, The Android Open Source Project
**
** Redistribution and use in source and binary forms, with or without
** modification, are permitted provided that the following conditions are met:
**     * Redistributions of source code must retain the above copyright
**       notice, this list of conditions and the following disclaimer.
**     * Redistributions in binary form must reproduce the above copyright
**       notice, this list of conditions and the following disclaimer in the
**       documentation and/or other materials provided with the distribution.
**     * Neither the name of The Android Open Source Project nor the names of
**       its contributors may be used to endorse or promote products derived
**       from this software without specific prior written permission.
**
** THIS SOFTWARE IS PROVIDED BY The Android Open Source Project ``AS IS'' AND
** ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
** IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
** ARE DISCLAIMED. IN NO EVENT SHALL The Android Open Source Project BE LIABLE
** FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
** DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
** SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
** CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
** LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
** OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
** DAMAGE.
*/

#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <stdarg.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>

#include <sys/ioctl.h>
#include <sys/mman.h>
#include <sys/time.h>

#include <linux/ioctl.h>
#define __force
#define __bitwise
#define __user
#include <sound/asound.h>

#include <tinyalsa/asoundlib.h>

#define PARAM_MAX SNDRV_PCM_HW_PARAM_LAST_INTERVAL

static inline int param_is_mask(int p)
{
    return (p >= SNDRV_PCM_HW_PARAM_FIRST_MASK) &&
        (p <= SNDRV_PCM_HW_PARAM_LAST_MASK);
}

static inline int param_is_interval(int p)
{
    return (p >= SNDRV_PCM_HW_PARAM_FIRST_INTERVAL) &&
        (p <= SNDRV_PCM_HW_PARAM_LAST_INTERVAL);
}

static inline struct snd_interval *param_to_interval(struct snd_pcm_hw_params *p, int n)
{
    return &(p->intervals[n - SNDRV_PCM_HW_PARAM_FIRST_INTERVAL]);
}

static inline struct snd_mask *param_to_mask(struct snd_pcm_hw_params *p, int n)
{
    return &(p->masks[n - SNDRV_PCM_HW_PARAM_FIRST_MASK]);
}

static void param_set_mask(struct snd_pcm_hw_params *p, int n, unsigned int bit)
{
    if (bit >= SNDRV_MASK_MAX)
        return;
    if (param_is_mask(n)) {
        struct snd_mask *m = param_to_mask(p, n);
        m->bits[0] = 0;
        m->bits[1] = 0;
        m->bits[bit >> 5] |= (1 << (bit & 31));
    }
}

static void param_set_min(struct snd_pcm_hw_params *p, int n, unsigned int val)
{
    if (param_is_interval(n)) {
        struct snd_interval *i = param_to_interval(p, n);
        i->min = val;
    }
}

static void param_set_max(struct snd_pcm_hw_params *p, int n, unsigned int val)
{
    if (param_is_interval(n)) {
        struct snd_interval *i = param_to_interval(p, n);
        i->max = val;
    }
}

static void param_set_int(struct snd_pcm_hw_params *p, int n, unsigned int val)
{
    if (param_is_interval(n)) {
        struct snd_interval *i = param_to_interval(p, n);
        i->min = val;
        i->max = val;
        i->integer = 1;
    }
}

static void param_init(struct snd_pcm_hw_params *p)
{
    int n;

    memset(p, 0, sizeof(*p));
    for (n = SNDRV_PCM_HW_PARAM_FIRST_MASK;
         n <= SNDRV_PCM_HW_PARAM_LAST_MASK; n++) {
            struct snd_mask *m = param_to_mask(p, n);
            m->bits[0] = ~0;
            m->bits[1] = ~0;
    }
    for (n = SNDRV_PCM_HW_PARAM_FIRST_INTERVAL;
         n <= SNDRV_PCM_HW_PARAM_LAST_INTERVAL; n++) {
            struct snd_interval *i = param_to_interval(p, n);
            i->min = 0;
            i->max = ~0;
    }
}

#define PCM_ERROR_MAX 128

struct pcm {
    int fd;
    unsigned int flags;
    int running:1;
    int underruns;
    unsigned int buffer_size;
    char error[PCM_ERROR_MAX];
    struct pcm_config config;
};

unsigned int pcm_get_buffer_size(struct pcm *pcm)
{
    return pcm->buffer_size;
}

const char* pcm_get_error(struct pcm *pcm)
{
    return pcm->error;
}

static int oops(struct pcm *pcm, int e, const char *fmt, ...)
{
    va_list ap;
    int sz;

    va_start(ap, fmt);
    vsnprintf(pcm->error, PCM_ERROR_MAX, fmt, ap);
    va_end(ap);
    sz = strlen(pcm->error);

    if (errno)
        snprintf(pcm->error + sz, PCM_ERROR_MAX - sz,
                 ": %s", strerror(e));
    return -1;
}

static unsigned int pcm_format_to_alsa(enum pcm_format format)
{
    switch (format) {
    case PCM_FORMAT_S32_LE:
        return SNDRV_PCM_FORMAT_S32_LE;
    default:
    case PCM_FORMAT_S16_LE:
        return SNDRV_PCM_FORMAT_S16_LE;
    };
}

static unsigned int pcm_format_to_bits(enum pcm_format format)
{
    switch (format) {
    case PCM_FORMAT_S32_LE:
        return 32;
    default:
    case PCM_FORMAT_S16_LE:
        return 16;
    };
}

int pcm_write(struct pcm *pcm, void *data, unsigned int count)
{
    struct snd_xferi x;

    if (pcm->flags & PCM_IN)
        return -EINVAL;

    x.buf = data;
    x.frames = count / (pcm->config.channels *
                        pcm_format_to_bits(pcm->config.format) / 8);

    for (;;) {
        if (!pcm->running) {
            if (ioctl(pcm->fd, SNDRV_PCM_IOCTL_PREPARE))
                return oops(pcm, errno, "cannot prepare channel");
            if (ioctl(pcm->fd, SNDRV_PCM_IOCTL_WRITEI_FRAMES, &x))
                return oops(pcm, errno, "cannot write initial data");
            pcm->running = 1;
            return 0;
        }
        if (ioctl(pcm->fd, SNDRV_PCM_IOCTL_WRITEI_FRAMES, &x)) {
            pcm->running = 0;
            if (errno == EPIPE) {
                    /* we failed to make our window -- try to restart */
                pcm->underruns++;
                continue;
            }
            return oops(pcm, errno, "cannot write stream data");
        }
        return 0;
    }
}

int pcm_read(struct pcm *pcm, void *data, unsigned int count)
{
    struct snd_xferi x;

    if (!(pcm->flags & PCM_IN))
        return -EINVAL;

    x.buf = data;
    x.frames = count / (pcm->config.channels *
                        pcm_format_to_bits(pcm->config.format) / 8);

    for (;;) {
        if (!pcm->running) {
            if (ioctl(pcm->fd, SNDRV_PCM_IOCTL_PREPARE))
                return oops(pcm, errno, "cannot prepare channel");
            if (ioctl(pcm->fd, SNDRV_PCM_IOCTL_START))
                return oops(pcm, errno, "cannot start channel");
            pcm->running = 1;
        }
        if (ioctl(pcm->fd, SNDRV_PCM_IOCTL_READI_FRAMES, &x)) {
            pcm->running = 0;
            if (errno == EPIPE) {
                    /* we failed to make our window -- try to restart */
                pcm->underruns++;
                continue;
            }
            return oops(pcm, errno, "cannot read stream data");
        }
        return 0;
    }
}

static struct pcm bad_pcm = {
    .fd = -1,
};

int pcm_close(struct pcm *pcm)
{
    if (pcm == &bad_pcm)
        return 0;

    if (pcm->fd >= 0)
        close(pcm->fd);
    pcm->running = 0;
    pcm->buffer_size = 0;
    pcm->fd = -1;
    return 0;
}

struct pcm *pcm_open(unsigned int card, unsigned int device,
                     unsigned int flags, struct pcm_config *config)
{
    struct pcm *pcm;
    struct snd_pcm_info info;
    struct snd_pcm_hw_params params;
    struct snd_pcm_sw_params sparams;
    char fn[256];

    pcm = calloc(1, sizeof(struct pcm));
    if (!pcm || !config)
        return &bad_pcm; /* TODO: could support default config here */

    pcm->config = *config;

    snprintf(fn, sizeof(fn), "/dev/snd/pcmC%uD%u%c", card, device,
             flags & PCM_IN ? 'c' : 'p');

    pcm->flags = flags;
    pcm->fd = open(fn, O_RDWR);
    if (pcm->fd < 0) {
        oops(pcm, errno, "cannot open device '%s'", fn);
        return pcm;
    }

    if (ioctl(pcm->fd, SNDRV_PCM_IOCTL_INFO, &info)) {
        oops(pcm, errno, "cannot get info");
        goto fail;
    }

    param_init(&params);
    param_set_mask(&params, SNDRV_PCM_HW_PARAM_ACCESS,
                   SNDRV_PCM_ACCESS_RW_INTERLEAVED);
    param_set_mask(&params, SNDRV_PCM_HW_PARAM_FORMAT,
                   pcm_format_to_alsa(config->format));
    param_set_mask(&params, SNDRV_PCM_HW_PARAM_SUBFORMAT,
                   SNDRV_PCM_SUBFORMAT_STD);
    param_set_min(&params, SNDRV_PCM_HW_PARAM_PERIOD_SIZE, config->period_size);
    param_set_int(&params, SNDRV_PCM_HW_PARAM_SAMPLE_BITS,
                  pcm_format_to_bits(config->format));
    param_set_int(&params, SNDRV_PCM_HW_PARAM_FRAME_BITS,
                  pcm_format_to_bits(config->format) * config->channels);
    param_set_int(&params, SNDRV_PCM_HW_PARAM_CHANNELS,
                  config->channels);
    param_set_int(&params, SNDRV_PCM_HW_PARAM_PERIODS, config->period_count);
    param_set_int(&params, SNDRV_PCM_HW_PARAM_RATE, config->rate);

    if (ioctl(pcm->fd, SNDRV_PCM_IOCTL_HW_PARAMS, &params)) {
        oops(pcm, errno, "cannot set hw params");
        goto fail;
    }

    memset(&sparams, 0, sizeof(sparams));
    sparams.tstamp_mode = SNDRV_PCM_TSTAMP_NONE;
    sparams.period_step = 1;
    sparams.avail_min = 1;
    sparams.start_threshold = config->period_count * config->period_size;
    sparams.stop_threshold = config->period_count * config->period_size;
    sparams.xfer_align = config->period_size / 2; /* needed for old kernels */
    sparams.silence_size = 0;
    sparams.silence_threshold = 0;

    if (ioctl(pcm->fd, SNDRV_PCM_IOCTL_SW_PARAMS, &sparams)) {
        oops(pcm, errno, "cannot set sw params");
        goto fail;
    }

    pcm->buffer_size = config->period_count * config->period_size;
    pcm->underruns = 0;
    return pcm;

fail:
    close(pcm->fd);
    pcm->fd = -1;
    return pcm;
}

int pcm_is_ready(struct pcm *pcm)
{
    return pcm->fd >= 0;
}

int pcm_start(struct pcm *pcm)
{
    if (ioctl(pcm->fd, SNDRV_PCM_IOCTL_PREPARE) < 0)
        return oops(pcm, errno, "cannot prepare channel");
    if (ioctl(pcm->fd, SNDRV_PCM_IOCTL_START) < 0)
        return oops(pcm, errno, "cannot start channel");

    return 0;
}

int pcm_stop(struct pcm *pcm)
{
    if (ioctl(pcm->fd, SNDRV_PCM_IOCTL_DROP) < 0)
        return oops(pcm, errno, "cannot stop channel");

    return 0;
}