| Message ID | 1544437996-1311-1-git-send-email-twischer@de.adit-jv.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [-,snd_pcm_extplug_set_param_link(),1/1] pcm: extplug: Keep format and channels the same if requested | expand |
On Mon, 10 Dec 2018 11:33:16 +0100, <twischer@de.adit-jv.com> wrote: > > From: Timo Wischer <twischer@de.adit-jv.com> > > 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> This looks much nicer, now with a proper documentation and a good example! Applied now, thanks. Takashi
diff --git a/include/pcm_extplug.h b/include/pcm_extplug.h index ced934f..e5c02d4 100644 --- a/include/pcm_extplug.h +++ b/include/pcm_extplug.h @@ -184,6 +184,8 @@ int snd_pcm_extplug_set_param_list(snd_pcm_extplug_t *extplug, int type, unsigne int snd_pcm_extplug_set_param_minmax(snd_pcm_extplug_t *extplug, int type, unsigned int min, unsigned int max); int snd_pcm_extplug_set_slave_param_list(snd_pcm_extplug_t *extplug, int type, unsigned int num_list, const unsigned int *list); int snd_pcm_extplug_set_slave_param_minmax(snd_pcm_extplug_t *extplug, int type, unsigned int min, unsigned int max); +int snd_pcm_extplug_set_param_link(snd_pcm_extplug_t *extplug, int type, + int keep_link); /** * set the parameter constraint with a single value diff --git a/src/pcm/pcm_ext_parm.h b/src/pcm/pcm_ext_parm.h index d25f2ab..7b99bef 100644 --- a/src/pcm/pcm_ext_parm.h +++ b/src/pcm/pcm_ext_parm.h @@ -5,6 +5,7 @@ struct snd_ext_parm { unsigned int *list; unsigned int active: 1; unsigned int integer: 1; + unsigned int keep_link: 1; }; static inline snd_mask_t *hw_param_mask(snd_pcm_hw_params_t *params, diff --git a/src/pcm/pcm_extplug.c b/src/pcm/pcm_extplug.c index 1f887c5..94002dc 100644 --- a/src/pcm/pcm_extplug.c +++ b/src/pcm/pcm_extplug.c @@ -249,7 +249,7 @@ static unsigned int get_links(struct snd_ext_parm *params) SND_PCM_HW_PARBIT_TICK_TIME); for (i = 0; i < SND_PCM_EXTPLUG_HW_PARAMS; i++) { - if (params[i].active) + if (params[i].active && !params[i].keep_link) links &= ~excl_parbits[i]; } return links; @@ -642,6 +642,17 @@ as former functions. To clear the parameter constraints, call #snd_pcm_extplug_params_reset() function. +When using snd_pcm_extplug_set_param_*() or snd_pcm_extplug_set_slave_param_*() +for any parameter. This parameter is no longer linked between the client and +slave PCM. Therefore it could differ and the extplug has to support conversion +between all valid parameter configurations. To keep the client and slave +parameter linked #snd_pcm_extplug_set_param_link() can be used for the +corresponding parameter. For example if the extplug does not support channel nor +format conversion the supported client parameters can be limited with +snd_pcm_extplug_set_param_*() and afterwards +#snd_pcm_extplug_set_param_link(ext, SND_PCM_EXTPLUG_HW_FORMAT, 1) and +#snd_pcm_extplug_set_param_link(ext, SND_PCM_EXTPLUG_HW_CHANNELS, 1) should be +called to keep the client and slave parameters the same. */ /** @@ -849,3 +860,26 @@ int snd_pcm_extplug_set_param_minmax(snd_pcm_extplug_t *extplug, int type, unsig return snd_ext_parm_set_minmax(&ext->params[type], min, max); } +/** + * @brief Keep the client and slave format/channels the same if requested. This + * is for example useful if this extplug does not support any channel + * conversion. + * @param extplug the extplug handle + * @param type parameter type + * @param keep_link if 1 the parameter identified by type will be kept the same + * for the client and slave PCM of this extplug + * @return 0 if successful, or a negative error code + */ +int snd_pcm_extplug_set_param_link(snd_pcm_extplug_t *extplug, int type, + int keep_link) +{ + extplug_priv_t *ext = extplug->pcm->private_data; + + if (type < 0 || type >= SND_PCM_EXTPLUG_HW_PARAMS) { + SNDERR("EXTPLUG: invalid parameter type %d", type); + return -EINVAL; + } + ext->params[type].keep_link = keep_link ? 1 : 0; + ext->sparams[type].keep_link = keep_link ? 1 : 0; + return 0; +}