src/audio/dma/SDL_dmaaudio.c

/*
  Simple DirectMedia Layer
  Copyright (C) 1997-2011 Sam Lantinga <slouken@libsdl.org>

  This software is provided 'as-is', without any express or implied
  warranty.  In no event will the authors be held liable for any damages
  arising from the use of this software.

  Permission is granted to anyone to use this software for any purpose,
  including commercial applications, and to alter it and redistribute it
  freely, subject to the following restrictions:

  1. The origin of this software must not be misrepresented; you must not
     claim that you wrote the original software. If you use this software
     in a product, an acknowledgment in the product documentation would be
     appreciated but is not required.
  2. Altered source versions must be plainly marked as such, and must not be
     misrepresented as being the original software.
  3. This notice may not be removed or altered from any source distribution.
*/
#include "SDL_config.h"

/* !!! FIXME: merge this driver with "dsp". */

/* 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_INPUT    (O_RDWR|O_NONBLOCK)
#define OPEN_FLAGS_OUTPUT   (O_RDWR|O_NONBLOCK)

static char **outputDevices = NULL;
static int outputDeviceCount = 0;
static char **inputDevices = NULL;
static int inputDeviceCount = 0;

static int
test_for_mmap(int fd)
{
    int caps = 0;
    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)) {
        size_t len = info.fragstotal * info.fragsize;
        Uint8 *buf = (Uint8 *) mmap(NULL, len, PROT_WRITE, MAP_SHARED, fd, 0);
        if (buf != MAP_FAILED) {
            munmap(buf, len);
            return 1;
        }
    }
    return 0;
}


static inline void
free_device_list(char ***devs, int *count)
{
    SDL_FreeUnixAudioDevices(devs, count);
}

static inline void
build_device_list(int iscapture, char ***devs, int *count)
{
    const int flags = ((iscapture) ? OPEN_FLAGS_INPUT : OPEN_FLAGS_OUTPUT);
    free_device_list(devs, count);
    SDL_EnumUnixAudioDevices(flags, 0, test_for_mmap, devs, count);
}

static inline void
build_device_lists(void)
{
    build_device_list(0, &outputDevices, &outputDeviceCount);
    build_device_list(1, &inputDevices, &inputDeviceCount);
}


static inline void
free_device_lists(void)
{
    free_device_list(&outputDevices, &outputDeviceCount);
    free_device_list(&inputDevices, &inputDeviceCount);
}


static void
DMA_Deinitialize(void)
{
    free_device_lists();
}

static int
DMA_DetectDevices(int iscapture)
{
    if (iscapture) {
        build_device_list(1, &inputDevices, &inputDeviceCount);
        return inputDeviceCount;
    } else {
        build_device_list(0, &outputDevices, &outputDeviceCount);
        return outputDeviceCount;
    }

    return 0;                   /* shouldn't ever hit this. */
}


static const char *
DMA_GetDeviceName(int index, int iscapture)
{
    if ((iscapture) && (index < inputDeviceCount)) {
        return inputDevices[index];
    } else if ((!iscapture) && (index < outputDeviceCount)) {
        return outputDevices[index];
    }

    SDL_SetError("No such device");
    return NULL;
}


static int
DMA_ReopenAudio(_THIS, const char *audiodev, int format, int stereo)
{
    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(&this->spec);

    /* Determine the power of two of the fragment size */
    for (frag_spec = 0; (0x01 << frag_spec) < this->spec.size; ++frag_spec);
    if ((0x01 << frag_spec) != this->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 = (this->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 = this->spec.freq;
    if (ioctl(audio_fd, SNDCTL_DSP_SPEED, &value) < 0) {
        SDL_SetError("Couldn't set audio frequency");
        return (-1);
    }
    this->spec.freq = value;

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


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


static int
DMA_OpenDevice(_THIS, const char *devname, int iscapture)
{
    const int flags = ((iscapture) ? OPEN_FLAGS_INPUT : OPEN_FLAGS_OUTPUT);
    int format;
    int stereo;
    int value;
    SDL_AudioFormat test_format;
    struct audio_buf_info info;

    /* We don't care what the devname is...we'll try to open anything. */
    /*  ...but default to first name in the list... */
    if (devname == NULL) {
        if (((iscapture) && (inputDeviceCount == 0)) ||
            ((!iscapture) && (outputDeviceCount == 0))) {
            SDL_SetError("No such audio device");
            return 0;
        }
        devname = ((iscapture) ? inputDevices[0] : outputDevices[0]);
    }

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

    /* Open the audio device */
    audio_fd = open(devname, flags, 0);
    if (audio_fd < 0) {
        DMA_CloseDevice(this);
        SDL_SetError("Couldn't open %s: %s", devname, strerror(errno));
        return 0;
    }
    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) {
        DMA_CloseDevice(this);
        SDL_SetError("Couldn't get audio format list");
        return 0;
    }

    /* Try for a closest match on audio format */
    format = 0;
    for (test_format = SDL_FirstAudioFormat(this->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) {
        DMA_CloseDevice(this);
        SDL_SetError("Couldn't find any hardware audio formats");
        return 0;
    }
    this->spec.format = test_format;

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

    /* Set mono or stereo audio (currently only two channels supported) */
    stereo = (this->spec.channels > 1);
    ioctl(audio_fd, SNDCTL_DSP_STEREO, &stereo);
    if (stereo) {
        this->spec.channels = 2;
    } else {
        this->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, devname, format, stereo) < 0) {
        DMA_CloseDevice(this);
        /* Error is set by DMA_ReopenAudio() */
        return 0;
    }

    /* Memory map the audio buffer */
    if (ioctl(audio_fd, SNDCTL_DSP_GETOSPACE, &info) < 0) {
        DMA_CloseDevice(this);
        SDL_SetError("Couldn't get OSPACE parameters");
        return 0;
    }
    this->spec.size = info.fragsize;
    this->spec.samples = this->spec.size / ((this->spec.format & 0xFF) / 8);
    this->spec.samples /= this->spec.channels;
    num_buffers = info.fragstotal;
    dma_len = num_buffers * this->spec.size;
    dma_buf = (Uint8 *) mmap(NULL, dma_len, PROT_WRITE, MAP_SHARED,
                             audio_fd, 0);
    if (dma_buf == MAP_FAILED) {
        DMA_CloseDevice(this);
        SDL_SetError("DMA memory map failed");
        dma_buf = NULL;
        return 0;
    }
    SDL_memset(dma_buf, this->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) (this->spec.samples * 1000) / this->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) {
        DMA_CloseDevice(this);
        SDL_SetError("Couldn't trigger audio output");
        return 0;
    }

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

    /* We're ready to rock and roll. :-) */
    return 1;
}


/* This function waits until it is possible to write a full sound buffer */
static void
DMA_WaitDevice(_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 && errno == ESRCH) {
                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_PlayDevice(_THIS)
{
    /* If timer synchronization is enabled, set the next write frame */
    if (frame_ticks) {
        next_frame += frame_ticks;
    }
    return;
}

static Uint8 *
DMA_GetDeviceBuf(_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 int
DMA_Init(SDL_AudioDriverImpl * impl)
{
    /* Set the function pointers */
    impl->DetectDevices = DMA_DetectDevices;
    impl->GetDeviceName = DMA_GetDeviceName;
    impl->OpenDevice = DMA_OpenDevice;
    impl->WaitDevice = DMA_WaitDevice;
    impl->PlayDevice = DMA_PlayDevice;
    impl->GetDeviceBuf = DMA_GetDeviceBuf;
    impl->CloseDevice = DMA_CloseDevice;
    impl->Deinitialize = DMA_Deinitialize;

    build_device_lists();

    return 1;   /* this audio target is available. */
}

AudioBootStrap DMA_bootstrap = {
    DMA_DRIVER_NAME, "OSS /dev/dsp DMA audio", DMA_Init, 0
};

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