oss.c - qemu - Git at Google

 /*
  * QEMU OSS Audio output driver
  *
  * Copyright (c) 2003 Vassili Karpov (malc)
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
  * in the Software without restriction, including without limitation the rights
  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  * copies of the Software, and to permit persons to whom the Software is
  * furnished to do so, subject to the following conditions:
  *
  * The above copyright notice and this permission notice shall be included in
  * all copies or substantial portions of the Software.
  *
  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  * THE SOFTWARE.
  */
 #include "vl.h"

 #if !defined(_WIN32) && !defined(__APPLE__)
 #include <ctype.h>
 #include <fcntl.h>
 #include <errno.h>
 #include <stdio.h>
 #include <unistd.h>
 #include <string.h>
 #include <stdlib.h>
 #include <limits.h>
 #include <inttypes.h>
 #include <sys/mman.h>
 #include <sys/types.h>
 #include <sys/ioctl.h>
 #include <sys/soundcard.h>


 /* http://www.df.lth.se/~john_e/gems/gem002d.html */
 /* http://www.multi-platforms.com/Tips/PopCount.htm */
 static inline uint32_t popcount (uint32_t u)
 {
   u = ((u&0x55555555) + ((u>>1)&0x55555555));
   u = ((u&0x33333333) + ((u>>2)&0x33333333));
   u = ((u&0x0f0f0f0f) + ((u>>4)&0x0f0f0f0f));
   u = ((u&0x00ff00ff) + ((u>>8)&0x00ff00ff));
   u = ( u&0x0000ffff) + (u>>16);
   return u;
 }

 static inline uint32_t lsbindex (uint32_t u)
 {
   return popcount ((u&-u)-1);
 }

 #define MIN(a, b) ((a)>(b)?(b):(a))
 #define MAX(a, b) ((a)<(b)?(b):(a))

 #define DEREF(x) (void)x
 #define log(...) fprintf (stderr, "oss: " __VA_ARGS__)
 #define ERRFail(...) do {                                       \
     int _errno = errno;                                         \
     fprintf (stderr, "oss: " __VA_ARGS__);                      \
     fprintf (stderr, "system error: %s\n", strerror (_errno));  \
     abort ();                                                   \
 } while (0)
 #define Fail(...) do {                          \
     fprintf (stderr, "oss: " __VA_ARGS__);      \
     fprintf (stderr, "\n");                     \
     abort ();                                   \
 } while (0)

 #ifdef DEBUG_OSS
 #define lwarn(...) fprintf (stderr, "oss: " __VA_ARGS__)
 #define linfo(...) fprintf (stderr, "oss: " __VA_ARGS__)
 #define ldebug(...) fprintf (stderr, "oss: " __VA_ARGS__)
 #else
 #define lwarn(...)
 #define linfo(...)
 #define ldebug(...)
 #endif


 #define IOCTL(args) do {                        \
   int ret = ioctl args;                         \
   if (-1 == ret) {                              \
     ERRFail (#args);                            \
   }                                             \
   ldebug ("ioctl " #args " = %d\n", ret);       \
 } while (0)

 static struct {
     int fd;
     int freq;
     int bits16;
     int nchannels;
     int rpos;
     int wpos;
     int live;
     int oss_fmt;
     int bytes_per_second;
     int is_mapped;
     void *buf;
     int bufsize;
     int nfrags;
     int fragsize;
     int old_optr;
     int leftover;
     uint64_t old_ticks;
     void (*copy_fn)(void *, void *, int);
 } oss = { .fd = -1 };

 static struct {
     int try_mmap;
     int nfrags;
     int fragsize;
 } conf = {
     .try_mmap = 0,
     .nfrags = 4,
     .fragsize = 4096
 };

 static enum {DONT, DSP, TID} est = DONT;

 static void copy_no_conversion (void *dst, void *src, int size)
 {
     memcpy (dst, src, size);
 }

 static void copy_u16_to_s16 (void *dst, void *src, int size)
 {
     int i;
     uint16_t *out, *in;

     out = dst;
     in = src;

     for (i = 0; i < size / 2; i++) {
         out[i] = in[i] + 0x8000;
     }
 }

 static void pab (struct audio_buf_info *abinfo)
 {
     DEREF (abinfo);

     ldebug ("fragments %d, fragstotal %d, fragsize %d, bytes %d\n"
             "rpos %d, wpos %d, live %d\n",
             abinfo->fragments,
             abinfo->fragstotal,
             abinfo->fragsize,
             abinfo->bytes,
             rpos, wpos, live);
 }

 static void do_open ()
 {
     int mmmmssss;
     audio_buf_info abinfo;
     int fmt, freq, nchannels;

     if (oss.buf) {
         if (-1 == munmap (oss.buf, oss.bufsize)) {
             ERRFail ("failed to unmap audio buffer %p %d",
                      oss.buf, oss.bufsize);
         }
         oss.buf = NULL;
     }

     if (-1 != oss.fd)
         close (oss.fd);

     oss.fd = open ("/dev/dsp", O_RDWR | O_NONBLOCK);
     if (-1 == oss.fd) {
         ERRFail ("can not open /dev/dsp");
     }

     fmt = oss.oss_fmt;
     freq = oss.freq;
     nchannels = oss.nchannels;

     IOCTL ((oss.fd, SNDCTL_DSP_RESET, 1));
     IOCTL ((oss.fd, SNDCTL_DSP_SAMPLESIZE, &fmt));
     IOCTL ((oss.fd, SNDCTL_DSP_CHANNELS, &nchannels));
     IOCTL ((oss.fd, SNDCTL_DSP_SPEED, &freq));
     IOCTL ((oss.fd, SNDCTL_DSP_NONBLOCK));

     mmmmssss = (conf.nfrags << 16) | conf.fragsize;
     IOCTL ((oss.fd, SNDCTL_DSP_SETFRAGMENT, &mmmmssss));

     if ((oss.oss_fmt != fmt)
         || (oss.nchannels != nchannels)
         || (oss.freq != freq)) {
         Fail ("failed to set audio parameters\n"
               "parameter | requested value | obtained value\n"
               "format    |      %10d |     %10d\n"
               "channels  |      %10d |     %10d\n"
               "frequency |      %10d |     %10d\n",
               oss.oss_fmt, fmt,
               oss.nchannels, nchannels,
               oss.freq, freq);
     }

     IOCTL ((oss.fd, SNDCTL_DSP_GETOSPACE, &abinfo));

     oss.nfrags = abinfo.fragstotal;
     oss.fragsize = abinfo.fragsize;
     oss.bufsize = oss.nfrags * oss.fragsize;
     oss.old_optr = 0;

     oss.bytes_per_second = (freq << (nchannels >> 1)) << oss.bits16;

     linfo ("bytes per second %d\n", oss.bytes_per_second);

     linfo ("fragments %d, fragstotal %d, fragsize %d, bytes %d, bufsize %d\n",
            abinfo.fragments,
            abinfo.fragstotal,
            abinfo.fragsize,
            abinfo.bytes,
            oss.bufsize);

     oss.buf = MAP_FAILED;
     oss.is_mapped = 0;

     if (conf.try_mmap) {
         oss.buf = mmap (NULL, oss.bufsize, PROT_WRITE, MAP_SHARED, oss.fd, 0);
         if (MAP_FAILED == oss.buf) {
             int err;

             err = errno;
             log ("failed to mmap audio, size %d, fd %d\n"
                  "syserr: %s\n",
                  oss.bufsize, oss.fd, strerror (err));
         }
     else {
             est = TID;
             oss.is_mapped = 1;
         }
     }

     if (MAP_FAILED == oss.buf) {
         est = TID;
         oss.buf = mmap (NULL, oss.bufsize, PROT_READ | PROT_WRITE,
                         MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
         if (MAP_FAILED == oss.buf) {
             ERRFail ("mmap audio buf, size %d", oss.bufsize);
         }
     }

     oss.rpos = 0;
     oss.wpos = 0;
     oss.live = 0;

     if (oss.is_mapped) {
         int trig;

         trig = 0;
         IOCTL ((oss.fd, SNDCTL_DSP_SETTRIGGER, &trig));
         trig = PCM_ENABLE_OUTPUT;
         IOCTL ((oss.fd, SNDCTL_DSP_SETTRIGGER, &trig));
     }
 }

 static void maybe_open (int req_freq, int req_nchannels,
                         audfmt_e req_fmt, int force_open)
 {
     int oss_fmt, bits16;

     switch (req_fmt) {
     case AUD_FMT_U8:
         bits16 = 0;
         oss_fmt = AFMT_U8;
         oss.copy_fn = copy_no_conversion;
         break;

     case AUD_FMT_S8:
         Fail ("can not play 8bit signed");

     case AUD_FMT_S16:
         bits16 = 1;
         oss_fmt = AFMT_S16_LE;
         oss.copy_fn = copy_no_conversion;
         break;

     case AUD_FMT_U16:
         bits16 = 1;
         oss_fmt = AFMT_S16_LE;
         oss.copy_fn = copy_u16_to_s16;
         break;

     default:
         abort ();
     }

     if (force_open
         || (-1 == oss.fd)
         || (oss_fmt != oss.oss_fmt)
         || (req_nchannels != oss.nchannels)
         || (req_freq != oss.freq)
         || (bits16 != oss.bits16)) {
         oss.oss_fmt = oss_fmt;
         oss.nchannels = req_nchannels;
         oss.freq = req_freq;
         oss.bits16 = bits16;
         do_open ();
     }
 }

 void AUD_reset (int req_freq, int req_nchannels, audfmt_e req_fmt)
 {
     maybe_open (req_freq, req_nchannels, req_fmt, 0);
 }

 void AUD_open (int req_freq, int req_nchannels, audfmt_e req_fmt)
 {
     maybe_open (req_freq, req_nchannels, req_fmt, 1);
 }

 int AUD_write (void *in_buf, int size)
 {
     int to_copy, temp;
     uint8_t *in, *out;

     to_copy = MIN (oss.bufsize - oss.live, size);

     temp = to_copy;

     in = in_buf;
     out = oss.buf;

     while (temp) {
         int copy;

         copy = MIN (temp, oss.bufsize - oss.wpos);
         oss.copy_fn (out + oss.wpos, in, copy);

         oss.wpos += copy;
         if (oss.wpos == oss.bufsize) {
             oss.wpos = 0;
         }

         temp -= copy;
         in += copy;
         oss.live += copy;
     }

     return to_copy;
 }

 void AUD_run (void)
 {
     int res;
     int bytes;
     struct audio_buf_info abinfo;

     if (0 == oss.live)
         return;

     if (oss.is_mapped) {
         count_info info;

         res = ioctl (oss.fd, SNDCTL_DSP_GETOPTR, &info);
         if (-1 == res) {
             int err;

             err = errno;
             lwarn ("SNDCTL_DSP_GETOPTR failed with %s\n", strerror (err));
             return;
         }

         if (info.ptr > oss.old_optr) {
             bytes = info.ptr - oss.old_optr;
         }
         else {
             bytes = oss.bufsize + info.ptr - oss.old_optr;
         }

         oss.old_optr = info.ptr;
         oss.live -= bytes;
         return;
     }

     res = ioctl (oss.fd, SNDCTL_DSP_GETOSPACE, &abinfo);

     if (-1 == res) {
         int err;

         err = errno;
         lwarn ("SNDCTL_DSP_GETOSPACE failed with %s\n", strerror (err));
     }

     bytes = abinfo.bytes;
     bytes = MIN (oss.live, bytes);
 #if 0
     bytes = (bytes / fragsize) * fragsize;
 #endif

     while (bytes) {
         int left, play, written;

         left = oss.bufsize - oss.rpos;
         play = MIN (left, bytes);
         written = write (oss.fd, (void *) ((uint32_t) oss.buf + oss.rpos), play);

         if (-1 == written) {
             if (EAGAIN == errno || EINTR == errno) {
                 return;
             }
             else {
                 ERRFail ("write audio");
             }
         }

         play = written;
         oss.live -= play;
         oss.rpos += play;
         bytes -= play;

         if (oss.rpos == oss.bufsize) {
             oss.rpos = 0;
         }
     }
 }

 static int get_dsp_bytes (void)
 {
     int res;
     struct count_info info;

     res = ioctl (oss.fd, SNDCTL_DSP_GETOPTR, &info);
     if (-1 == res) {
         int err;

         err = errno;
         lwarn ("SNDCTL_DSP_GETOPTR failed with %s\n", strerror (err));
         return -1;
     }
     else {
         ldebug ("bytes %d\n", info.bytes);
         return info.bytes;
     }
 }

 void AUD_adjust_estimate (int leftover)
 {
     oss.leftover = leftover;
 }

 int AUD_get_free (void)
 {
     int free, elapsed;

     free = oss.bufsize - oss.live;

     if (0 == free)
         return 0;

     elapsed = free;
     switch (est) {
     case DONT:
         break;

     case DSP:
         {
             static int old_bytes;
             int bytes;

             bytes = get_dsp_bytes ();
             if (bytes <= 0)
                 return free;

             elapsed = bytes - old_bytes;
             old_bytes = bytes;
             ldebug ("dsp elapsed %d bytes\n", elapsed);
             break;
         }

     case TID:
         {
             uint64_t ticks, delta;
             uint64_t ua_elapsed;
             uint64_t al_elapsed;

             ticks = qemu_get_clock(rt_clock);
             delta = ticks - oss.old_ticks;
             oss.old_ticks = ticks;

             ua_elapsed = (delta * oss.bytes_per_second) / 1000;
             al_elapsed = ua_elapsed & ~3ULL;

             ldebug ("tid elapsed %llu bytes\n", ua_elapsed);

             if (al_elapsed > (uint64_t) INT_MAX)
                 elapsed = INT_MAX;
             else
                 elapsed = al_elapsed;

             elapsed += oss.leftover;
         }
     }

     if (elapsed > free) {
         lwarn ("audio can not keep up elapsed %d free %d\n", elapsed, free);
         return free;
     }
     else {
         return elapsed;
     }
 }

 int AUD_get_live (void)
 {
     return oss.live;
 }

 int AUD_get_buffer_size (void)
 {
     return oss.bufsize;
 }

 #define QC_OSS_FRAGSIZE "QEMU_OSS_FRAGSIZE"
 #define QC_OSS_NFRAGS "QEMU_OSS_NFRAGS"
 #define QC_OSS_MMAP "QEMU_OSS_MMAP"

 static int get_conf_val (const char *key, int defval)
 {
     int val = defval;
     char *strval;

     strval = getenv (key);
     if (strval) {
         val = atoi (strval);
     }

     return val;
 }

 void AUD_init (void)
 {
     int fsp;

     DEREF (pab);

     conf.fragsize = get_conf_val (QC_OSS_FRAGSIZE, conf.fragsize);
     conf.nfrags = get_conf_val (QC_OSS_NFRAGS, conf.nfrags);
     conf.try_mmap = get_conf_val (QC_OSS_MMAP, conf.try_mmap);

     fsp = conf.fragsize;
     if (0 != (fsp & (fsp - 1))) {
         Fail ("fragment size %d is not power of 2", fsp);
     }

     conf.fragsize = lsbindex (fsp);
 }

 #else

 void AUD_run (void)
 {
 }

 int AUD_write (void *in_buf, int size)
 {
     return 0;
 }

 void AUD_reset (int rfreq, int rnchannels, audfmt_e rfmt)
 {
 }

 void AUD_adjust_estimate (int _leftover)
 {
 }

 int AUD_get_free (void)
 {
     return 0;
 }

 int AUD_get_live (void)
 {
     return 0;
 }

 int AUD_get_buffer_size (void)
 {
     return 0;
 }

 void AUD_init (void)
 {
 }

 #endif
	/*
	* QEMU OSS Audio output driver
	*
	* Copyright (c) 2003 Vassili Karpov (malc)
	*
	* Permission is hereby granted, free of charge, to any person obtaining a copy
	* of this software and associated documentation files (the "Software"), to deal
	* in the Software without restriction, including without limitation the rights
	* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
	* copies of the Software, and to permit persons to whom the Software is
	* furnished to do so, subject to the following conditions:
	*
	* The above copyright notice and this permission notice shall be included in
	* all copies or substantial portions of the Software.
	*
	* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
	* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
	* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
	* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
	* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
	* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
	* THE SOFTWARE.
	*/
	#include "vl.h"

	#if !defined(_WIN32) && !defined(__APPLE__)
	#include <ctype.h>
	#include <fcntl.h>
	#include <errno.h>
	#include <stdio.h>
	#include <unistd.h>
	#include <string.h>
	#include <stdlib.h>
	#include <limits.h>
	#include <inttypes.h>
	#include <sys/mman.h>
	#include <sys/types.h>
	#include <sys/ioctl.h>
	#include <sys/soundcard.h>


	/* http://www.df.lth.se/~john_e/gems/gem002d.html */
	/* http://www.multi-platforms.com/Tips/PopCount.htm */
	static inline uint32_t popcount (uint32_t u)
	{
	u = ((u&0x55555555) + ((u>>1)&0x55555555));
	u = ((u&0x33333333) + ((u>>2)&0x33333333));
	u = ((u&0x0f0f0f0f) + ((u>>4)&0x0f0f0f0f));
	u = ((u&0x00ff00ff) + ((u>>8)&0x00ff00ff));
	u = ( u&0x0000ffff) + (u>>16);
	return u;
	}

	static inline uint32_t lsbindex (uint32_t u)
	{
	return popcount ((u&-u)-1);
	}

	#define MIN(a, b) ((a)>(b)?(b):(a))
	#define MAX(a, b) ((a)<(b)?(b):(a))

	#define DEREF(x) (void)x
	#define log(...) fprintf (stderr, "oss: " __VA_ARGS__)
	#define ERRFail(...) do { \
	int _errno = errno; \
	fprintf (stderr, "oss: " __VA_ARGS__); \
	fprintf (stderr, "system error: %s\n", strerror (_errno)); \
	abort (); \
	} while (0)
	#define Fail(...) do { \
	fprintf (stderr, "oss: " __VA_ARGS__); \
	fprintf (stderr, "\n"); \
	abort (); \
	} while (0)

	#ifdef DEBUG_OSS
	#define lwarn(...) fprintf (stderr, "oss: " __VA_ARGS__)
	#define linfo(...) fprintf (stderr, "oss: " __VA_ARGS__)
	#define ldebug(...) fprintf (stderr, "oss: " __VA_ARGS__)
	#else
	#define lwarn(...)
	#define linfo(...)
	#define ldebug(...)
	#endif


	#define IOCTL(args) do { \
	int ret = ioctl args; \
	if (-1 == ret) { \
	ERRFail (#args); \
	} \
	ldebug ("ioctl " #args " = %d\n", ret); \
	} while (0)

	static struct {
	int fd;
	int freq;
	int bits16;
	int nchannels;
	int rpos;
	int wpos;
	int live;
	int oss_fmt;
	int bytes_per_second;
	int is_mapped;
	void *buf;
	int bufsize;
	int nfrags;
	int fragsize;
	int old_optr;
	int leftover;
	uint64_t old_ticks;
	void (copy_fn)(void , void *, int);
	} oss = { .fd = -1 };

	static struct {
	int try_mmap;
	int nfrags;
	int fragsize;
	} conf = {
	.try_mmap = 0,
	.nfrags = 4,
	.fragsize = 4096
	};

	static enum {DONT, DSP, TID} est = DONT;

	static void copy_no_conversion (void dst, void src, int size)
	{
	memcpy (dst, src, size);
	}

	static void copy_u16_to_s16 (void dst, void src, int size)
	{
	int i;
	uint16_t out, in;

	out = dst;
	in = src;

	for (i = 0; i < size / 2; i++) {
	out[i] = in[i] + 0x8000;
	}
	}

	static void pab (struct audio_buf_info *abinfo)
	{
	DEREF (abinfo);

	ldebug ("fragments %d, fragstotal %d, fragsize %d, bytes %d\n"
	"rpos %d, wpos %d, live %d\n",
	abinfo->fragments,
	abinfo->fragstotal,
	abinfo->fragsize,
	abinfo->bytes,
	rpos, wpos, live);
	}

	static void do_open ()
	{
	int mmmmssss;
	audio_buf_info abinfo;
	int fmt, freq, nchannels;

	if (oss.buf) {
	if (-1 == munmap (oss.buf, oss.bufsize)) {
	ERRFail ("failed to unmap audio buffer %p %d",
	oss.buf, oss.bufsize);
	}
	oss.buf = NULL;
	}

	if (-1 != oss.fd)
	close (oss.fd);

	oss.fd = open ("/dev/dsp", O_RDWR \| O_NONBLOCK);
	if (-1 == oss.fd) {
	ERRFail ("can not open /dev/dsp");
	}

	fmt = oss.oss_fmt;
	freq = oss.freq;
	nchannels = oss.nchannels;

	IOCTL ((oss.fd, SNDCTL_DSP_RESET, 1));
	IOCTL ((oss.fd, SNDCTL_DSP_SAMPLESIZE, &fmt));
	IOCTL ((oss.fd, SNDCTL_DSP_CHANNELS, &nchannels));
	IOCTL ((oss.fd, SNDCTL_DSP_SPEED, &freq));
	IOCTL ((oss.fd, SNDCTL_DSP_NONBLOCK));

	mmmmssss = (conf.nfrags << 16) \| conf.fragsize;
	IOCTL ((oss.fd, SNDCTL_DSP_SETFRAGMENT, &mmmmssss));

	if ((oss.oss_fmt != fmt)
	\|\| (oss.nchannels != nchannels)
	\|\| (oss.freq != freq)) {
	Fail ("failed to set audio parameters\n"
	"parameter \| requested value \| obtained value\n"
	"format \| %10d \| %10d\n"
	"channels \| %10d \| %10d\n"
	"frequency \| %10d \| %10d\n",
	oss.oss_fmt, fmt,
	oss.nchannels, nchannels,
	oss.freq, freq);
	}

	IOCTL ((oss.fd, SNDCTL_DSP_GETOSPACE, &abinfo));

	oss.nfrags = abinfo.fragstotal;
	oss.fragsize = abinfo.fragsize;
	oss.bufsize = oss.nfrags * oss.fragsize;
	oss.old_optr = 0;

	oss.bytes_per_second = (freq << (nchannels >> 1)) << oss.bits16;

	linfo ("bytes per second %d\n", oss.bytes_per_second);

	linfo ("fragments %d, fragstotal %d, fragsize %d, bytes %d, bufsize %d\n",
	abinfo.fragments,
	abinfo.fragstotal,
	abinfo.fragsize,
	abinfo.bytes,
	oss.bufsize);

	oss.buf = MAP_FAILED;
	oss.is_mapped = 0;

	if (conf.try_mmap) {
	oss.buf = mmap (NULL, oss.bufsize, PROT_WRITE, MAP_SHARED, oss.fd, 0);
	if (MAP_FAILED == oss.buf) {
	int err;

	err = errno;
	log ("failed to mmap audio, size %d, fd %d\n"
	"syserr: %s\n",
	oss.bufsize, oss.fd, strerror (err));
	}
	else {
	est = TID;
	oss.is_mapped = 1;
	}
	}

	if (MAP_FAILED == oss.buf) {
	est = TID;
	oss.buf = mmap (NULL, oss.bufsize, PROT_READ \| PROT_WRITE,
	MAP_ANONYMOUS \| MAP_PRIVATE, -1, 0);
	if (MAP_FAILED == oss.buf) {
	ERRFail ("mmap audio buf, size %d", oss.bufsize);
	}
	}

	oss.rpos = 0;
	oss.wpos = 0;
	oss.live = 0;

	if (oss.is_mapped) {
	int trig;

	trig = 0;
	IOCTL ((oss.fd, SNDCTL_DSP_SETTRIGGER, &trig));
	trig = PCM_ENABLE_OUTPUT;
	IOCTL ((oss.fd, SNDCTL_DSP_SETTRIGGER, &trig));
	}
	}

	static void maybe_open (int req_freq, int req_nchannels,
	audfmt_e req_fmt, int force_open)
	{
	int oss_fmt, bits16;

	switch (req_fmt) {
	case AUD_FMT_U8:
	bits16 = 0;
	oss_fmt = AFMT_U8;
	oss.copy_fn = copy_no_conversion;
	break;

	case AUD_FMT_S8:
	Fail ("can not play 8bit signed");

	case AUD_FMT_S16:
	bits16 = 1;
	oss_fmt = AFMT_S16_LE;
	oss.copy_fn = copy_no_conversion;
	break;

	case AUD_FMT_U16:
	bits16 = 1;
	oss_fmt = AFMT_S16_LE;
	oss.copy_fn = copy_u16_to_s16;
	break;

	default:
	abort ();
	}

	if (force_open
	\|\| (-1 == oss.fd)
	\|\| (oss_fmt != oss.oss_fmt)
	\|\| (req_nchannels != oss.nchannels)
	\|\| (req_freq != oss.freq)
	\|\| (bits16 != oss.bits16)) {
	oss.oss_fmt = oss_fmt;
	oss.nchannels = req_nchannels;
	oss.freq = req_freq;
	oss.bits16 = bits16;
	do_open ();
	}
	}

	void AUD_reset (int req_freq, int req_nchannels, audfmt_e req_fmt)
	{
	maybe_open (req_freq, req_nchannels, req_fmt, 0);
	}

	void AUD_open (int req_freq, int req_nchannels, audfmt_e req_fmt)
	{
	maybe_open (req_freq, req_nchannels, req_fmt, 1);
	}

	int AUD_write (void *in_buf, int size)
	{
	int to_copy, temp;
	uint8_t in, out;

	to_copy = MIN (oss.bufsize - oss.live, size);

	temp = to_copy;

	in = in_buf;
	out = oss.buf;

	while (temp) {
	int copy;

	copy = MIN (temp, oss.bufsize - oss.wpos);
	oss.copy_fn (out + oss.wpos, in, copy);

	oss.wpos += copy;
	if (oss.wpos == oss.bufsize) {
	oss.wpos = 0;
	}

	temp -= copy;
	in += copy;
	oss.live += copy;
	}

	return to_copy;
	}

	void AUD_run (void)
	{
	int res;
	int bytes;
	struct audio_buf_info abinfo;

	if (0 == oss.live)
	return;

	if (oss.is_mapped) {
	count_info info;

	res = ioctl (oss.fd, SNDCTL_DSP_GETOPTR, &info);
	if (-1 == res) {
	int err;

	err = errno;
	lwarn ("SNDCTL_DSP_GETOPTR failed with %s\n", strerror (err));
	return;
	}

	if (info.ptr > oss.old_optr) {
	bytes = info.ptr - oss.old_optr;
	}
	else {
	bytes = oss.bufsize + info.ptr - oss.old_optr;
	}

	oss.old_optr = info.ptr;
	oss.live -= bytes;
	return;
	}

	res = ioctl (oss.fd, SNDCTL_DSP_GETOSPACE, &abinfo);

	if (-1 == res) {
	int err;

	err = errno;
	lwarn ("SNDCTL_DSP_GETOSPACE failed with %s\n", strerror (err));
	}

	bytes = abinfo.bytes;
	bytes = MIN (oss.live, bytes);
	#if 0
	bytes = (bytes / fragsize) * fragsize;
	#endif

	while (bytes) {
	int left, play, written;

	left = oss.bufsize - oss.rpos;
	play = MIN (left, bytes);
	written = write (oss.fd, (void *) ((uint32_t) oss.buf + oss.rpos), play);

	if (-1 == written) {
	if (EAGAIN == errno \|\| EINTR == errno) {
	return;
	}
	else {
	ERRFail ("write audio");
	}
	}

	play = written;
	oss.live -= play;
	oss.rpos += play;
	bytes -= play;

	if (oss.rpos == oss.bufsize) {
	oss.rpos = 0;
	}
	}
	}

	static int get_dsp_bytes (void)
	{
	int res;
	struct count_info info;

	res = ioctl (oss.fd, SNDCTL_DSP_GETOPTR, &info);
	if (-1 == res) {
	int err;

	err = errno;
	lwarn ("SNDCTL_DSP_GETOPTR failed with %s\n", strerror (err));
	return -1;
	}
	else {
	ldebug ("bytes %d\n", info.bytes);
	return info.bytes;
	}
	}

	void AUD_adjust_estimate (int leftover)
	{
	oss.leftover = leftover;
	}

	int AUD_get_free (void)
	{
	int free, elapsed;

	free = oss.bufsize - oss.live;

	if (0 == free)
	return 0;

	elapsed = free;
	switch (est) {
	case DONT:
	break;

	case DSP:
	{
	static int old_bytes;
	int bytes;

	bytes = get_dsp_bytes ();
	if (bytes <= 0)
	return free;

	elapsed = bytes - old_bytes;
	old_bytes = bytes;
	ldebug ("dsp elapsed %d bytes\n", elapsed);
	break;
	}

	case TID:
	{
	uint64_t ticks, delta;
	uint64_t ua_elapsed;
	uint64_t al_elapsed;

	ticks = qemu_get_clock(rt_clock);
	delta = ticks - oss.old_ticks;
	oss.old_ticks = ticks;

	ua_elapsed = (delta * oss.bytes_per_second) / 1000;
	al_elapsed = ua_elapsed & ~3ULL;

	ldebug ("tid elapsed %llu bytes\n", ua_elapsed);

	if (al_elapsed > (uint64_t) INT_MAX)
	elapsed = INT_MAX;
	else
	elapsed = al_elapsed;

	elapsed += oss.leftover;
	}
	}

	if (elapsed > free) {
	lwarn ("audio can not keep up elapsed %d free %d\n", elapsed, free);
	return free;
	}
	else {
	return elapsed;
	}
	}

	int AUD_get_live (void)
	{
	return oss.live;
	}

	int AUD_get_buffer_size (void)
	{
	return oss.bufsize;
	}

	#define QC_OSS_FRAGSIZE "QEMU_OSS_FRAGSIZE"
	#define QC_OSS_NFRAGS "QEMU_OSS_NFRAGS"
	#define QC_OSS_MMAP "QEMU_OSS_MMAP"

	static int get_conf_val (const char *key, int defval)
	{
	int val = defval;
	char *strval;

	strval = getenv (key);
	if (strval) {
	val = atoi (strval);
	}

	return val;
	}

	void AUD_init (void)
	{
	int fsp;

	DEREF (pab);

	conf.fragsize = get_conf_val (QC_OSS_FRAGSIZE, conf.fragsize);
	conf.nfrags = get_conf_val (QC_OSS_NFRAGS, conf.nfrags);
	conf.try_mmap = get_conf_val (QC_OSS_MMAP, conf.try_mmap);

	fsp = conf.fragsize;
	if (0 != (fsp & (fsp - 1))) {
	Fail ("fragment size %d is not power of 2", fsp);
	}

	conf.fragsize = lsbindex (fsp);
	}

	#else

	void AUD_run (void)
	{
	}

	int AUD_write (void *in_buf, int size)
	{
	return 0;
	}

	void AUD_reset (int rfreq, int rnchannels, audfmt_e rfmt)
	{
	}

	void AUD_adjust_estimate (int _leftover)
	{
	}

	int AUD_get_free (void)
	{
	return 0;
	}

	int AUD_get_live (void)
	{
	return 0;
	}

	int AUD_get_buffer_size (void)
	{
	return 0;
	}

	void AUD_init (void)
	{
	}

	#endif