[alsa-devel] Getting pcm_usb_stream plugin to know its limits. [Kind of SOLVED]

[Michaël Cadilhac]

michael at cadilhac.name (Michaël Cadilhac) writes:

> michael at cadilhac.name (Michaël Cadilhac) writes:
>
>> So, my final saying is the following patch.  It fixes the segfault on
>> stopping a non-started usb_stream, plus it adds the ability to set a
>> period size and sound rate.  The latter offers a workaround for the
>> second issue I came with (that the default values for period bytes, and
>> hence period size, were too high for us122l to work).
>
> Any comment on that patch would be greatly appreciated.  I'm just
> wondering if it's safe for me to give it to some people.

Anyone?  Note that this also fixes a real bug, so it might be of
interest to include it in the trunk.

>> --- /dd/alsa-plugins/usb_stream/pcm_usb_stream.c	2008-11-21 18:08:16.000000000 -0500
>> +++ pcm_usb_stream.c	2009-12-30 23:40:46.467973740 -0500
>> @@ -48,6 +48,9 @@
>>  #define VDBG(f, ...)
>>  #endif
>>  
>> +#define FRAME_SIZE 6
>> +
>> +
>>  #define LCARD 32
>>  struct user_usb_stream {
>>  	char			card[LCARD];
>> @@ -70,6 +73,8 @@
>>  	unsigned		periods_done;
>>  
>>  	unsigned 		channels;
>> +	snd_pcm_uframes_t	period_size;
>> +	unsigned int		rate;
>>  } snd_pcm_us_t;
>>  
>>  static struct user_usb_stream *uus;
>> @@ -177,7 +182,7 @@
>>  	VDBG("");
>>  
>>  	us_cfg.version = USB_STREAM_INTERFACE_VERSION;
>> -	us_cfg.frame_size = 6;
>> +	us_cfg.frame_size = FRAME_SIZE;
>>  	us_cfg.sample_rate = io->rate;
>>  	us_cfg.period_frames = io->period_size;
>>  
>> @@ -256,8 +261,11 @@
>>  static int snd_pcm_us_stop(snd_pcm_ioplug_t *io)
>>  {
>>  	snd_pcm_us_t *us = io->private_data;
>> -	VDBG("%u", us->uus->s->periods_done);
>>  
>> +	if (!us->uus->s)
>> +	  return 0;
>> +
>> +	VDBG("%u", us->uus->s->periods_done);
>>  	if (io->stream == SND_PCM_STREAM_PLAYBACK)
>>  		memset(us->uus->write_area, 0, us->uus->s->write_size);
>>  
>> @@ -370,6 +378,10 @@
>>  	};
>>  
>>  	int err;
>> +	unsigned int rate_min = us->rate ? us->rate : 44100,
>> +		rate_max = us->rate ? us->rate : 96000,
>> +		period_bytes_min = us->period_size ? FRAME_SIZE * us->period_size : 128,
>> +		period_bytes_max = us->period_size ? FRAME_SIZE * us->period_size : 64*4096;
>>  
>>  	if ((err = snd_pcm_ioplug_set_param_list(&us->io, SND_PCM_IOPLUG_HW_ACCESS,
>>  						 ARRAY_SIZE(access_list), access_list)) < 0 ||
>> @@ -378,19 +390,20 @@
>>  	    (err = snd_pcm_ioplug_set_param_minmax(&us->io, SND_PCM_IOPLUG_HW_CHANNELS,
>>  						   us->channels, us->channels)) < 0 ||
>>  	    (err = snd_pcm_ioplug_set_param_minmax(&us->io, SND_PCM_IOPLUG_HW_RATE,
>> -						   44100, 96000)) < 0 ||
>> +						   rate_min, rate_max)) < 0 ||
>>  	    (err = snd_pcm_ioplug_set_param_minmax(&us->io, SND_PCM_IOPLUG_HW_PERIOD_BYTES,
>> -						   128, 64*4096)) < 0 ||
>> +						   period_bytes_min, period_bytes_max)) < 0 ||
>>  	    (err = snd_pcm_ioplug_set_param_minmax(&us->io, SND_PCM_IOPLUG_HW_PERIODS,
>>  						   2, 2)) < 0)
>>  		return err;
>> -
>>  	return 0;
>>  }
>>  
>>  static int snd_pcm_us_open(snd_pcm_t **pcmp, const char *name,
>>  				   const char *card,
>> -				   snd_pcm_stream_t stream, int mode)
>> +			   snd_pcm_stream_t stream, int mode,
>> +			   snd_pcm_uframes_t period_size,
>> +			   unsigned int rate)
>>  {
>>  	snd_pcm_us_t *us;
>>  	int err;
>> @@ -421,6 +434,8 @@
>>  	snd_hwdep_poll_descriptors(us->hwdep, &us->pfd, 1);
>>  
>>  	us->channels = 2;
>> +	us->period_size = period_size;
>> +	us->rate = rate;
>>  
>>  	us->io.version = SND_PCM_IOPLUG_VERSION;
>>  	us->io.name = "ALSA <-> USB_STREAM PCM I/O Plugin";
>> @@ -455,6 +470,7 @@
>>  	snd_config_iterator_t i, next;
>>  	const char *card;
>>  	int err;
>> +	long period_size = 0, rate = 0;
>>  	
>>  	snd_config_for_each(i, next, conf) {
>>  		snd_config_t *n = snd_config_iterator_entry(i);
>> @@ -472,12 +488,27 @@
>>  			snd_config_get_string(n, &card);
>>  			continue;
>>  		}
>> +		if (strcmp(id, "period_size") == 0) {
>> +			if (snd_config_get_type(n) != SND_CONFIG_TYPE_INTEGER) {
>> +				SNDERR("Invalid type for %s", id);
>> +				return -EINVAL;
>> +			}
>> +			snd_config_get_integer(n, &period_size);
>> +			continue;
>> +		}
>> +		if (strcmp(id, "rate") == 0) {
>> +			if (snd_config_get_type(n) != SND_CONFIG_TYPE_INTEGER) {
>> +				SNDERR("Invalid type for %s", id);
>> +				return -EINVAL;
>> +			}
>> +			snd_config_get_integer(n, &rate);
>> +			continue;
>> +		}
>>  		SNDERR("Unknown field %s", id);
>>  		return -EINVAL;
>>  	}
>>  
>> -	err = snd_pcm_us_open(pcmp, name, card, stream, mode);
>> -
>> +	err = snd_pcm_us_open(pcmp, name, card, stream, mode, period_size, rate);
>>  	return err;
>>  }

-- 
Michaël `Micha' Cadilhac (LITQ, U. de Montréal) -- http://michael.cadilhac.name
	||   21 seems like a good value: half of 42,
	||    and just old enough to drink!  Why would you want to change it?
	||         -- Stefan Monnier