Kontron KTAM3874-pITX - Manual (Page 108)

KTD-S0057-I Page 104 Linux® Programming Examples (DebianTM)
KTAM3874/pITX Software Guide
/* Transfer method - direct write only using mmap_write functions */
static int direct_write_loop (snd_pcm_t *handle, signed short *samples, snd_pcm_channel_area_t *areas)
{
double phase = 0;
signed short *ptr;
int err, cptr;
while (1)
{
generate_sine (areas, 0, period_size, &phase);
ptr = samples;
cptr = period_size;
while (cptr > 0)
{
err = snd_pcm_mmap_writei (handle, ptr, cptr);
if (err == -EAGAIN)
continue;
if (err < 0)
{
if (xrun_recovery (handle, err) < 0)
{
printf ("Write error: %s\n", snd_strerror (err));
exit (EXIT_FAILURE);
}
break; /* skip one period */
}
ptr += err * channels;
cptr -= err;
}
}
}
static struct transfer_method transfer_methods[] =
{
{ "write", SND_PCM_ACCESS_RW_INTERLEAVED, write_loop },
{ "write_and_poll", SND_PCM_ACCESS_RW_INTERLEAVED, write_and_poll_loop },
{ "async", SND_PCM_ACCESS_RW_INTERLEAVED, async_loop },
{ "async_direct", SND_PCM_ACCESS_MMAP_INTERLEAVED, async_direct_loop },
{ "direct_interleaved", SND_PCM_ACCESS_MMAP_INTERLEAVED, direct_loop },
{ "direct_noninterleaved", SND_PCM_ACCESS_MMAP_NONINTERLEAVED, direct_loop },
{ "direct_write", SND_PCM_ACCESS_MMAP_INTERLEAVED, direct_write_loop },
{ NULL, SND_PCM_ACCESS_RW_INTERLEAVED, NULL }
};
static void help (void)
{
int
k;