Hello,

I'll try again with a more specific question.

Is there a way one can access the hw_params that cause the SND_PCM_HOOK_TYPE_HW_PARAMS call back to be called inside the call back function?

The hook only provides access to the snd_pcm_t object, but all the public calls to get hw_params fail because it's not in a prepared state yet.

If there isn't a way to get them now could we please add the ability with a patch like the one below?

With this patch a call to snd_pcm_hook_get_hw_params provides access to the pending hw_params structure and the pending parameters can be accessed with standard calls like snd_pcm_hw_params_get_channels.

Hopefully I'm just missing how to get them without the patch, but if not they really should be made accessible.

diff --git a/alsa-lib-1.1.8/include/pcm.h b/pcm.h index 5b07823..0cf5dca 100644 --- a/alsa-lib-1.1.8/include/pcm.h +++ b/pcm.h @@ -1181,6 +1181,7 @@ typedef struct _snd_pcm_hook snd_pcm_hook_t; /** PCM hook callback function */ typedef int (*snd_pcm_hook_func_t)(snd_pcm_hook_t *hook); snd_pcm_t *snd_pcm_hook_get_pcm(snd_pcm_hook_t *hook); +snd_pcm_hw_params_t *snd_pcm_hook_get_hw_params(snd_pcm_hook_t *hook); void *snd_pcm_hook_get_private(snd_pcm_hook_t *hook); void snd_pcm_hook_set_private(snd_pcm_hook_t *hook, void *private_data); int snd_pcm_hook_add(snd_pcm_hook_t **hookp, snd_pcm_t *pcm,

diff --git a/alsa-lib-1.1.8/src/pcm/pcm_hooks.c b/pcm_hooks.c index 4416d36..f56c3af 100644 --- a/alsa-lib-1.1.8/src/pcm/pcm_hooks.c +++ b/pcm_hooks.c @@ -38,6 +38,7 @@ const char *_snd_module_pcm_hooks = ""; #ifndef DOC_HIDDEN struct _snd_pcm_hook { snd_pcm_t *pcm; + snd_pcm_hw_params_t *params; snd_pcm_hook_func_t func; void *private_data; struct list_head list; @@ -117,6 +118,7 @@ static int snd_pcm_hooks_hw_params(snd_pcm_t *pcm, snd_pcm_hw_params_t *params) return err; list_for_each_safe(pos, next, &h->hooks[SND_PCM_HOOK_TYPE_HW_PARAMS]) { snd_pcm_hook_t *hook = list_entry(pos, snd_pcm_hook_t, list); + hook->params = params; err = hook->func(hook); if (err < 0) return err; @@ -563,6 +565,17 @@ snd_pcm_t *snd_pcm_hook_get_pcm(snd_pcm_hook_t *hook) return hook->pcm; }

+/** + * \brief Get hw_params handle for a PCM hook + * \param hook PCM hook handle + * \return hw_params handle + */ +snd_pcm_hw_params_t *snd_pcm_hook_get_hw_params(snd_pcm_hook_t *hook) +{ + assert(hook); + return hook->params; +} + /** * \brief Get callback function private data for a PCM hook * \param hook PCM hook handle @@ -609,6 +622,7 @@ int snd_pcm_hook_add(snd_pcm_hook_t **hookp, snd_pcm_t *pcm, if (!h) return -ENOMEM; h->pcm = pcm; + h->params = NULL; h->func = func; h->private_data = private_data; hooks = pcm->private_data;