From: Alex Wiggins alex.d.wiggins@gmail.com

Added 3 user variables to control the OSS period and buffer config:

- period_size (integer): if not set then queries OSS for period size (by using SNDCTL_DSP_GETBLKSIZE), if positive then sets the OSS period size (SND_PCM_IOPLUG_HW_PERIOD_BYTES), if negative then allows any power of 2 period size.

- periods (integer): sets the number of OSS periods (SND_PCM_IOPLUG_HW_PERIODS);

- buffer_size (integer): sets the OSS buffer size (SND_PCM_IOPLUG_HW_BUFFER_BYTES).

Note that ALSA performs sanity checks to prevent conflicts.

Signed-off-by: Alex Wiggins alex.d.wiggins@gmail.com

diff --git a/oss/pcm_oss.c b/oss/pcm_oss.c index d5b5bc4..a92c3e9 100644 --- a/oss/pcm_oss.c +++ b/oss/pcm_oss.c @@ -60,6 +60,12 @@ typedef struct snd_pcm_oss { unsigned int period_shift; unsigned int periods; unsigned int frame_bytes; + /* user variables set using ALSA config files */ + /* included here as this snd_pcm_oss_t struct + is stored in io->private_data */ + long int user_period_size; + long int user_periods; + long int user_buffer_size; } snd_pcm_oss_t;

static snd_pcm_sframes_t oss_write(snd_pcm_ioplug_t *io, @@ -408,6 +414,7 @@ static int oss_hw_constraint(snd_pcm_oss_t *oss) unsigned int nchannels; unsigned int channel[6]; /* period and buffer bytes must be power of two */ + /* minimum: 2^8 = 256; maximum: 2^23 = 8388608 */ static const unsigned int bytes_list[] = { 1U<<8, 1U<<9, 1U<<10, 1U<<11, 1U<<12, 1U<<13, 1U<<14, 1U<<15, 1U<<16, 1U<<17, 1U<<18, 1U<<19, 1U<<20, 1U<<21, 1U<<22, 1U<<23 @@ -500,20 +507,97 @@ static int oss_hw_constraint(snd_pcm_oss_t *oss) if (err < 0) return err;

- /* period size (in power of two) */ - err = snd_pcm_ioplug_set_param_list(io, SND_PCM_IOPLUG_HW_PERIOD_BYTES, - ARRAY_SIZE(bytes_list), bytes_list); - if (err < 0) - return err; - /* periods */ - err = snd_pcm_ioplug_set_param_minmax(io, SND_PCM_IOPLUG_HW_PERIODS, 2, 1024); - if (err < 0) - return err; - /* buffer size (in power of two) */ - err = snd_pcm_ioplug_set_param_list(io, SND_PCM_IOPLUG_HW_BUFFER_BYTES, - ARRAY_SIZE(bytes_list), bytes_list); - if (err < 0) - return err; + /* period and buffer sizes: default behaviour below is to + query period size from OSS */ + + /* consider user set paramaters + (period_size; periods; buffer_size) */ + + /* note: ALSA performs sanity checks + to prevent conflicting parameters */ + + /* period_size */ + if (oss->user_period_size < 0) { + /* period_size set to negative value: + allow any power of 2 period size */ + err = snd_pcm_ioplug_set_param_list(io, + SND_PCM_IOPLUG_HW_PERIOD_BYTES, + ARRAY_SIZE(bytes_list), bytes_list); + if (err < 0) + return err; + } else { + if (oss->user_period_size > 0) { + /* period_size set to positive value: + use user set period size */ + const unsigned int user_period_size + = oss->user_period_size; + err = snd_pcm_ioplug_set_param_list(io, + SND_PCM_IOPLUG_HW_PERIOD_BYTES, 1, + &user_period_size); + } else { + /* query OSS for period size (called fragment size) */ + unsigned int fragsize; + if (ioctl(oss->fd, SNDCTL_DSP_GETBLKSIZE, &fragsize) + < 0) + fprintf(stderr, +"*** alsa-plugins-oss: error querying SNDCTL_DSP_GETBLKSIZE.\n"); + + /* note: second query of SNDCTL_DSP_GETBLKSIZE + can give different result + (i.e. 4096 instead of 2048) */ + /* in oss_audio_core.c getblksize function, + 4096 is the default return value: + so second time probably not reliable */ + + /* period size (in power of two) */ + unsigned int x = fragsize; + /* check if fragsize is a power of two */ + if ((x != 0) && ((x & (~x + 1)) == x)) + err = snd_pcm_ioplug_set_param_list(io, + SND_PCM_IOPLUG_HW_PERIOD_BYTES, + 1, &fragsize); + else + err = snd_pcm_ioplug_set_param_list(io, + SND_PCM_IOPLUG_HW_PERIOD_BYTES, + ARRAY_SIZE(bytes_list), bytes_list); + if (err < 0) + return err; + } + } + + /* periods (number of periods per buffer) */ + if (oss->user_periods > 0) { + /* force number of periods to user set periods */ + const unsigned int user_periods = oss->user_periods; + err = snd_pcm_ioplug_set_param_list(io, + SND_PCM_IOPLUG_HW_PERIODS, 1, &user_periods); + if (err < 0) + return err; + } else { + /* allow any number of periods between 2 and 1024 inclusive + (ALSA can choose) */ + err = snd_pcm_ioplug_set_param_minmax(io, + SND_PCM_IOPLUG_HW_PERIODS, 2, 1024); + if (err < 0) + return err; + } + + /* buffer_size */ + if (oss->user_buffer_size > 0) { + /* force buffer size to user set buffer_size */ + const unsigned int user_buffer_size = oss->user_buffer_size; + err = snd_pcm_ioplug_set_param_list(io, + SND_PCM_IOPLUG_HW_BUFFER_BYTES, 1, &user_buffer_size); + if (err < 0) + return err; + } else { + /* buffer size (in power of two) */ + err = snd_pcm_ioplug_set_param_list(io, + SND_PCM_IOPLUG_HW_BUFFER_BYTES, + ARRAY_SIZE(bytes_list), bytes_list); + if (err < 0) + return err; + }

return 0; } @@ -558,6 +642,10 @@ SND_PCM_PLUGIN_DEFINE_FUNC(oss) const char *device = "/dev/dsp"; int err; snd_pcm_oss_t *oss; + /* default values for user variables*/ + long int user_period_size = 0; + long int user_periods = 0; + long int user_buffer_size = 0; snd_config_for_each(i, next, conf) { snd_config_t *n = snd_config_iterator_entry(i); @@ -573,6 +661,30 @@ SND_PCM_PLUGIN_DEFINE_FUNC(oss) } continue; } + + /* user variables */ + if (strcmp(id, "period_size") == 0) { + if (snd_config_get_integer(n, &user_period_size) < 0) { + SNDERR("Invalid type for %s", id); + return -EINVAL; + } + continue; + } + if (strcmp(id, "periods") == 0) { + if (snd_config_get_integer(n, &user_periods) < 0) { + SNDERR("Invalid type for %s", id); + return -EINVAL; + } + continue; + } + if (strcmp(id, "buffer_size") == 0) { + if (snd_config_get_integer(n, &user_buffer_size) < 0) { + SNDERR("Invalid type for %s", id); + return -EINVAL; + } + continue; + } + SNDERR("Unknown field %s", id); return -EINVAL; } @@ -597,6 +709,11 @@ SND_PCM_PLUGIN_DEFINE_FUNC(oss) goto error; }

+ /* save user variables from ALSA config files */ + oss->user_period_size = user_period_size; + oss->user_periods = user_periods; + oss->user_buffer_size = user_buffer_size; + oss->io.version = SND_PCM_IOPLUG_VERSION; oss->io.name = "ALSA <-> OSS PCM I/O Plugin"; oss->io.poll_fd = oss->fd;