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Improve hw_params documentation

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Signed-off-by: Takashi Iwai <tiwai@suse.de>
This commit is contained in:
Andrew Eikum 2012-01-19 12:36:39 +01:00 • committed by Takashi Iwai
parent 235aec0a75
commit 43956de710
2 changed files with 25 additions and 2 deletions
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17
include/pcm.h
View file

@ -44,8 +44,23 @@ extern "C" {
/** PCM generic info container */ /** PCM generic info container */
typedef struct _snd_pcm_info snd_pcm_info_t; typedef struct _snd_pcm_info snd_pcm_info_t;
/** PCM hardware configuration space container */
/** PCM hardware configuration space container
*
* snd_pcm_hw_params_t is an opaque structure which contains a set of possible
* PCM hardware configurations. For example, a given instance might include a
* range of buffer sizes, a range of period sizes, and a set of several sample
* formats. Some subset of all possible combinations these sets may be valid,
* but not necessarily any combination will be valid.
*
* When a parameter is set or restricted using a snd_pcm_hw_params_set*
* function, all of the other ranges will be updated to exclude as many
* impossible configurations as possible. Attempting to set a parameter
* outside of its acceptable range will result in the function failing
* and an error code being returned.
*/
typedef struct _snd_pcm_hw_params snd_pcm_hw_params_t; typedef struct _snd_pcm_hw_params snd_pcm_hw_params_t;
/** PCM software configuration container */ /** PCM software configuration container */
typedef struct _snd_pcm_sw_params snd_pcm_sw_params_t; typedef struct _snd_pcm_sw_params snd_pcm_sw_params_t;
/** PCM status container */ /** PCM status container */

10
src/pcm/pcm.c
View file

@ -809,7 +809,9 @@ int snd_pcm_hw_params_current(snd_pcm_t *pcm, snd_pcm_hw_params_t *params)
* *
* The configuration is chosen fixing single parameters in this order: * The configuration is chosen fixing single parameters in this order:
* first access, first format, first subformat, min channels, min rate, * first access, first format, first subformat, min channels, min rate,
* min period time, max buffer size, min tick time * min period time, max buffer size, min tick time. If no mutually
* compatible set of parameters can be chosen, a negative error code
* will be returned.
* *
* After this call, #snd_pcm_prepare() is called automatically and * After this call, #snd_pcm_prepare() is called automatically and
* the stream is brought to \c #SND_PCM_STATE_PREPARED state. * the stream is brought to \c #SND_PCM_STATE_PREPARED state.
@ -817,6 +819,9 @@ int snd_pcm_hw_params_current(snd_pcm_t *pcm, snd_pcm_hw_params_t *params)
* The hardware parameters cannot be changed when the stream is * The hardware parameters cannot be changed when the stream is
* running (active). The software parameters can be changed * running (active). The software parameters can be changed
* at any time. * at any time.
*
* The configuration space will be updated to reflect the chosen
* parameters.
*/ */
int snd_pcm_hw_params(snd_pcm_t *pcm, snd_pcm_hw_params_t *params) int snd_pcm_hw_params(snd_pcm_t *pcm, snd_pcm_hw_params_t *params)
{ {
@ -3183,6 +3188,9 @@ int snd_pcm_hw_params_get_fifo_size(const snd_pcm_hw_params_t *params)
* \brief Fill params with a full configuration space for a PCM * \brief Fill params with a full configuration space for a PCM
* \param pcm PCM handle * \param pcm PCM handle
* \param params Configuration space * \param params Configuration space
*
* The configuration space will be filled with all possible ranges
* for the PCM device.
*/ */
int snd_pcm_hw_params_any(snd_pcm_t *pcm, snd_pcm_hw_params_t *params) int snd_pcm_hw_params_any(snd_pcm_t *pcm, snd_pcm_hw_params_t *params)
{ {