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https://github.com/alsa-project/alsa-lib.git
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ee64b4b83a
Without this patch it is not possible to link the channel and format
parameter if snd_pcm_extplug_set_param_*() or
snd_pcm_extplug_set_slave_param_*() is called. Therefore the client and
slave parameter can differ. So the extplug has to implement conversion.
To avoid this the new snd_pcm_extplug_set_param_link() function can be
called.
As a reproduction sceanrio the following extplug source code can be used:
===
static snd_pcm_sframes_t my_transfer(snd_pcm_extplug_t *e,
const snd_pcm_channel_area_t *da, snd_pcm_uframes_t dof,
const snd_pcm_channel_area_t *sa, snd_pcm_uframes_t sof,
snd_pcm_uframes_t s) {
return s;
}
static const snd_pcm_extplug_callback_t my_own_callback = {
.transfer = my_transfer
};
SND_PCM_PLUGIN_DEFINE_FUNC(my_plug) {
snd_config_iterator_t i, next;
snd_config_t *slave = NULL;
snd_pcm_extplug_t *myplug;
snd_config_for_each(i, next, conf) {
snd_config_t *n = snd_config_iterator_entry(i);
const char *id;
if (snd_config_get_id(n, &id) < 0)
continue;
if (strcmp(id, "comment") == 0 || strcmp(id, "type") == 0)
continue;
if (strcmp(id, "slave") == 0) {
slave = n;
continue;
}
return -EINVAL;
}
myplug = calloc(1, sizeof(*myplug));
myplug->version = SND_PCM_EXTPLUG_VERSION;
myplug->callback = &my_own_callback;
snd_pcm_extplug_create(myplug, name, root, slave, stream, mode);
snd_pcm_extplug_set_param_minmax(myplug,
SND_PCM_EXTPLUG_HW_CHANNELS, 1, 16);
// snd_pcm_extplug_set_param_link(myplug, SND_PCM_EXTPLUG_HW_CHANNELS, 1);
*pcmp = myplug->pcm;
return 0;
}
SND_PCM_PLUGIN_SYMBOL(my_plug);
===
To use this plugin the following ALSA configuration is required:
pcm.myplug {
type my_plug
slave.pcm hw:Dummy
}
With this configuration without this patch
snd_pcm_hw_params_get_channels_max() will always return 16 channels
independent of the supported channels of the dummy device. Due to that for
example the start up of JACK would fail:
$ modprobe snd_dummy
$ jackd -d alsa -P myplug
ALSA: cannot set channel count to 16 for playback
ALSA: cannot configure playback channel
Signed-off-by: Timo Wischer <twischer@de.adit-jv.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
42 lines
1.4 KiB
C
42 lines
1.4 KiB
C
/* hw_params */
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struct snd_ext_parm {
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unsigned int min, max;
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unsigned int num_list;
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unsigned int *list;
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unsigned int active: 1;
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unsigned int integer: 1;
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unsigned int keep_link: 1;
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};
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static inline snd_mask_t *hw_param_mask(snd_pcm_hw_params_t *params,
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snd_pcm_hw_param_t var)
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{
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return ¶ms->masks[var - SND_PCM_HW_PARAM_FIRST_MASK];
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}
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static inline snd_interval_t *hw_param_interval(snd_pcm_hw_params_t *params,
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snd_pcm_hw_param_t var)
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{
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return ¶ms->intervals[var - SND_PCM_HW_PARAM_FIRST_INTERVAL];
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}
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/* make local functions really local */
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#define snd_ext_parm_set_minmax \
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snd1_ext_parm_set_minmax
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#define snd_ext_parm_set_list \
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snd1_ext_parm_set_list
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#define snd_ext_parm_clear \
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snd1_ext_parm_clear
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#define snd_interval_list \
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snd1_interval_list
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#define snd_ext_parm_interval_refine \
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snd1_ext_parm_interval_refine
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#define snd_ext_parm_mask_refine \
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snd1_ext_parm_mask_refine
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int snd_ext_parm_set_minmax(struct snd_ext_parm *parm, unsigned int min, unsigned int max);
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int snd_ext_parm_set_list(struct snd_ext_parm *parm, unsigned int num_list, const unsigned int *list);
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void snd_ext_parm_clear(struct snd_ext_parm *parm);
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int snd_interval_list(snd_interval_t *ival, int num_list, unsigned int *list);
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int snd_ext_parm_interval_refine(snd_interval_t *ival, struct snd_ext_parm *parm, int type);
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int snd_ext_parm_mask_refine(snd_mask_t *mask, struct snd_ext_parm *parm, int type);
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