src/audio/dma/SDL_dmaaudio.c

/*
    SDL - Simple DirectMedia Layer
    Copyright (C) 1997-2006 Sam Lantinga

    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Lesser General Public
    License as published by the Free Software Foundation; either
    version 2.1 of the License, or (at your option) any later version.

    This library is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
    Lesser General Public License for more details.

    You should have received a copy of the GNU Lesser General Public
    License along with this library; if not, write to the Free Software
    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA

    Sam Lantinga
    slouken@libsdl.org
*/
#include "SDL_config.h"

/* Allow access to a raw mixing buffer */

#include <stdio.h>
#include <string.h>             /* For strerror() */
#include <errno.h>
#include <unistd.h>
#include <fcntl.h>
#include <signal.h>
#include <sys/types.h>
#include <sys/time.h>
#include <sys/ioctl.h>
#include <sys/stat.h>
#include <sys/mman.h>

#if SDL_AUDIO_DRIVER_OSS_SOUNDCARD_H
/* This is installed on some systems */
#include <soundcard.h>
#else
/* This is recommended by OSS */
#include <sys/soundcard.h>
#endif

#ifndef MAP_FAILED
#define MAP_FAILED	((Uint8 *)-1)
#endif

#include "SDL_timer.h"
#include "SDL_audio.h"
#include "../SDL_audio_c.h"
#include "../SDL_audiodev_c.h"
#include "SDL_dmaaudio.h"

/* The tag name used by DMA audio */
#define DMA_DRIVER_NAME         "dma"

/* Open the audio device for playback, and don't block if busy */
#define OPEN_FLAGS	(O_RDWR|O_NONBLOCK)

/* Audio driver functions */
static int DMA_OpenAudio(_THIS, SDL_AudioSpec * spec);
static void DMA_WaitAudio(_THIS);
static void DMA_PlayAudio(_THIS);
static Uint8 *DMA_GetAudioBuf(_THIS);
static void DMA_CloseAudio(_THIS);

/* Audio driver bootstrap functions */

static int
Audio_Available(void)
{
    int available;
    int fd;

    available = 0;

    fd = SDL_OpenAudioPath(NULL, 0, OPEN_FLAGS, 0);
    if (fd >= 0) {
        int caps;
        struct audio_buf_info info;

        if ((ioctl(fd, SNDCTL_DSP_GETCAPS, &caps) == 0) &&
            (caps & DSP_CAP_TRIGGER) && (caps & DSP_CAP_MMAP) &&
            (ioctl(fd, SNDCTL_DSP_GETOSPACE, &info) == 0)) {
            available = 1;
        }
        close(fd);
    }
    return (available);
}

static void
Audio_DeleteDevice(SDL_AudioDevice * device)
{
    SDL_free(device->hidden);
    SDL_free(device);
}

static SDL_AudioDevice *
Audio_CreateDevice(int devindex)
{
    SDL_AudioDevice *this;

    /* Initialize all variables that we clean on shutdown */
    this = (SDL_AudioDevice *) SDL_malloc(sizeof(SDL_AudioDevice));
    if (this) {
        SDL_memset(this, 0, (sizeof *this));
        this->hidden = (struct SDL_PrivateAudioData *)
            SDL_malloc((sizeof *this->hidden));
    }
    if ((this == NULL) || (this->hidden == NULL)) {
        SDL_OutOfMemory();
        if (this) {
            SDL_free(this);
        }
        return (0);
    }
    SDL_memset(this->hidden, 0, (sizeof *this->hidden));
    audio_fd = -1;

    /* Set the function pointers */
    this->OpenAudio = DMA_OpenAudio;
    this->WaitAudio = DMA_WaitAudio;
    this->PlayAudio = DMA_PlayAudio;
    this->GetAudioBuf = DMA_GetAudioBuf;
    this->CloseAudio = DMA_CloseAudio;

    this->free = Audio_DeleteDevice;

    return this;
}

AudioBootStrap DMA_bootstrap = {
    DMA_DRIVER_NAME, "OSS /dev/dsp DMA audio",
    Audio_Available, Audio_CreateDevice
};

/* This function waits until it is possible to write a full sound buffer */
static void
DMA_WaitAudio(_THIS)
{
    fd_set fdset;

    /* Check to see if the thread-parent process is still alive */
    {
        static int cnt = 0;
        /* Note that this only works with thread implementations 
           that use a different process id for each thread.
         */
        if (parent && (((++cnt) % 10) == 0)) {  /* Check every 10 loops */
            if (kill(parent, 0) < 0) {
                this->enabled = 0;
            }
        }
    }

    /* See if we need to use timed audio synchronization */
    if (frame_ticks) {
        /* Use timer for general audio synchronization */
        Sint32 ticks;

        ticks = ((Sint32) (next_frame - SDL_GetTicks())) - FUDGE_TICKS;
        if (ticks > 0) {
            SDL_Delay(ticks);
        }
    } else {
        /* Use select() for audio synchronization */
        struct timeval timeout;
        FD_ZERO(&fdset);
        FD_SET(audio_fd, &fdset);
        timeout.tv_sec = 10;
        timeout.tv_usec = 0;
#ifdef DEBUG_AUDIO
        fprintf(stderr, "Waiting for audio to get ready\n");
#endif
        if (select(audio_fd + 1, NULL, &fdset, NULL, &timeout) <= 0) {
            const char *message =
#ifdef AUDIO_OSPACE_HACK
                "Audio timeout - buggy audio driver? (trying ospace)";
#else
                "Audio timeout - buggy audio driver? (disabled)";
#endif
            /* In general we should never print to the screen,
               but in this case we have no other way of letting
               the user know what happened.
             */
            fprintf(stderr, "SDL: %s\n", message);
#ifdef AUDIO_OSPACE_HACK
            /* We may be able to use GET_OSPACE trick */
            frame_ticks = (float) (this->spec->samples * 1000) /
                this->spec->freq;
            next_frame = SDL_GetTicks() + frame_ticks;
#else
            this->enabled = 0;
            /* Don't try to close - may hang */
            audio_fd = -1;
#ifdef DEBUG_AUDIO
            fprintf(stderr, "Done disabling audio\n");
#endif
#endif /* AUDIO_OSPACE_HACK */
        }
#ifdef DEBUG_AUDIO
        fprintf(stderr, "Ready!\n");
#endif
    }
}

static void
DMA_PlayAudio(_THIS)
{
    /* If timer synchronization is enabled, set the next write frame */
    if (frame_ticks) {
        next_frame += frame_ticks;
    }
    return;
}

static Uint8 *
DMA_GetAudioBuf(_THIS)
{
    count_info info;
    int playing;
    int filling;

    /* Get number of blocks, looping if we're not using select() */
    do {
        if (ioctl(audio_fd, SNDCTL_DSP_GETOPTR, &info) < 0) {
            /* Uh oh... */
            this->enabled = 0;
            return (NULL);
        }
    }
    while (frame_ticks && (info.blocks < 1));
#ifdef DEBUG_AUDIO
    if (info.blocks > 1) {
        printf("Warning: audio underflow (%d frags)\n", info.blocks - 1);
    }
#endif
    playing = info.ptr / this->spec.size;
    filling = (playing + 1) % num_buffers;
    return (dma_buf + (filling * this->spec.size));
}

static void
DMA_CloseAudio(_THIS)
{
    if (dma_buf != NULL) {
        munmap(dma_buf, dma_len);
        dma_buf = NULL;
    }
    if (audio_fd >= 0) {
        close(audio_fd);
        audio_fd = -1;
    }
}

static int
DMA_ReopenAudio(_THIS, const char *audiodev, int format, int stereo,
                SDL_AudioSpec * spec)
{
    int frag_spec;
    int value;

    /* Close and then reopen the audio device */
    close(audio_fd);
    audio_fd = open(audiodev, O_RDWR, 0);
    if (audio_fd < 0) {
        SDL_SetError("Couldn't open %s: %s", audiodev, strerror(errno));
        return (-1);
    }

    /* Calculate the final parameters for this audio specification */
    SDL_CalculateAudioSpec(spec);

    /* Determine the power of two of the fragment size */
    for (frag_spec = 0; (0x01 << frag_spec) < spec->size; ++frag_spec);
    if ((0x01 << frag_spec) != spec->size) {
        SDL_SetError("Fragment size must be a power of two");
        return (-1);
    }

    /* Set the audio buffering parameters */
    if (ioctl(audio_fd, SNDCTL_DSP_SETFRAGMENT, &frag_spec) < 0) {
        SDL_SetError("Couldn't set audio fragment spec");
        return (-1);
    }

    /* Set the audio format */
    value = format;
    if ((ioctl(audio_fd, SNDCTL_DSP_SETFMT, &value) < 0) || (value != format)) {
        SDL_SetError("Couldn't set audio format");
        return (-1);
    }

    /* Set mono or stereo audio */
    value = (spec->channels > 1);
    if ((ioctl(audio_fd, SNDCTL_DSP_STEREO, &stereo) < 0) ||
        (value != stereo)) {
        SDL_SetError("Couldn't set audio channels");
        return (-1);
    }

    /* Set the DSP frequency */
    value = spec->freq;
    if (ioctl(audio_fd, SNDCTL_DSP_SPEED, &value) < 0) {
        SDL_SetError("Couldn't set audio frequency");
        return (-1);
    }
    spec->freq = value;

    /* We successfully re-opened the audio */
    return (0);
}

static int
DMA_OpenAudio(_THIS, SDL_AudioSpec * spec)
{
    char audiodev[1024];
    int format;
    int stereo;
    int value;
    SDL_AudioFormat test_format;
    struct audio_buf_info info;

    /* Reset the timer synchronization flag */
    frame_ticks = 0.0;

    /* Open the audio device */
    audio_fd = SDL_OpenAudioPath(audiodev, sizeof(audiodev), OPEN_FLAGS, 0);
    if (audio_fd < 0) {
        SDL_SetError("Couldn't open %s: %s", audiodev, strerror(errno));
        return (-1);
    }
    dma_buf = NULL;
    ioctl(audio_fd, SNDCTL_DSP_RESET, 0);

    /* Get a list of supported hardware formats */
    if (ioctl(audio_fd, SNDCTL_DSP_GETFMTS, &value) < 0) {
        SDL_SetError("Couldn't get audio format list");
        return (-1);
    }

    /* Try for a closest match on audio format */
    format = 0;
    for (test_format = SDL_FirstAudioFormat(spec->format);
         !format && test_format;) {
#ifdef DEBUG_AUDIO
        fprintf(stderr, "Trying format 0x%4.4x\n", test_format);
#endif
        switch (test_format) {
        case AUDIO_U8:
            if (value & AFMT_U8) {
                format = AFMT_U8;
            }
            break;
        case AUDIO_S8:
            if (value & AFMT_S8) {
                format = AFMT_S8;
            }
            break;
        case AUDIO_S16LSB:
            if (value & AFMT_S16_LE) {
                format = AFMT_S16_LE;
            }
            break;
        case AUDIO_S16MSB:
            if (value & AFMT_S16_BE) {
                format = AFMT_S16_BE;
            }
            break;
        case AUDIO_U16LSB:
            if (value & AFMT_U16_LE) {
                format = AFMT_U16_LE;
            }
            break;
        case AUDIO_U16MSB:
            if (value & AFMT_U16_BE) {
                format = AFMT_U16_BE;
            }
            break;
        default:
            format = 0;
            break;
        }
        if (!format) {
            test_format = SDL_NextAudioFormat();
        }
    }
    if (format == 0) {
        SDL_SetError("Couldn't find any hardware audio formats");
        return (-1);
    }
    spec->format = test_format;

    /* Set the audio format */
    value = format;
    if ((ioctl(audio_fd, SNDCTL_DSP_SETFMT, &value) < 0) || (value != format)) {
        SDL_SetError("Couldn't set audio format");
        return (-1);
    }

    /* Set mono or stereo audio (currently only two channels supported) */
    stereo = (spec->channels > 1);
    ioctl(audio_fd, SNDCTL_DSP_STEREO, &stereo);
    if (stereo) {
        spec->channels = 2;
    } else {
        spec->channels = 1;
    }

    /* Because some drivers don't allow setting the buffer size
       after setting the format, we must re-open the audio device
       once we know what format and channels are supported
     */
    if (DMA_ReopenAudio(this, audiodev, format, stereo, spec) < 0) {
        /* Error is set by DMA_ReopenAudio() */
        return (-1);
    }

    /* Memory map the audio buffer */
    if (ioctl(audio_fd, SNDCTL_DSP_GETOSPACE, &info) < 0) {
        SDL_SetError("Couldn't get OSPACE parameters");
        return (-1);
    }
    spec->size = info.fragsize;
    spec->samples = spec->size / ((spec->format & 0xFF) / 8);
    spec->samples /= spec->channels;
    num_buffers = info.fragstotal;
    dma_len = num_buffers * spec->size;
    dma_buf = (Uint8 *) mmap(NULL, dma_len, PROT_WRITE, MAP_SHARED,
                             audio_fd, 0);
    if (dma_buf == MAP_FAILED) {
        SDL_SetError("DMA memory map failed");
        dma_buf = NULL;
        return (-1);
    }
    SDL_memset(dma_buf, spec->silence, dma_len);

    /* Check to see if we need to use select() workaround */
    {
        char *workaround;
        workaround = SDL_getenv("SDL_DSP_NOSELECT");
        if (workaround) {
            frame_ticks = (float) (spec->samples * 1000) / spec->freq;
            next_frame = SDL_GetTicks() + frame_ticks;
        }
    }

    /* Trigger audio playback */
    value = 0;
    ioctl(audio_fd, SNDCTL_DSP_SETTRIGGER, &value);
    value = PCM_ENABLE_OUTPUT;
    if (ioctl(audio_fd, SNDCTL_DSP_SETTRIGGER, &value) < 0) {
        SDL_SetError("Couldn't trigger audio output");
        return (-1);
    }

    /* Get the parent process id (we're the parent of the audio thread) */
    parent = getpid();

    /* We're ready to rock and roll. :-) */
    return (0);
}

/* vi: set ts=4 sw=4 expandtab: */