diff options
| -rw-r--r-- | Documentation/sound/alsa/DocBook/alsa-driver-api.tmpl | 4 | ||||
| -rw-r--r-- | include/sound/control.h | 32 | ||||
| -rw-r--r-- | sound/core/vmaster.c | 16 |
3 files changed, 50 insertions, 2 deletions
diff --git a/Documentation/sound/alsa/DocBook/alsa-driver-api.tmpl b/Documentation/sound/alsa/DocBook/alsa-driver-api.tmpl index 9d644f7e241e..115962827c81 100644 --- a/Documentation/sound/alsa/DocBook/alsa-driver-api.tmpl +++ b/Documentation/sound/alsa/DocBook/alsa-driver-api.tmpl @@ -71,6 +71,10 @@ !Esound/pci/ac97/ac97_codec.c !Esound/pci/ac97/ac97_pcm.c </sect1> + <sect1><title>Virtual Master Control API</title> +!Esound/core/vmaster.c +!Iinclude/sound/control.h + </sect1> </chapter> <chapter><title>MIDI API</title> <sect1><title>Raw MIDI API</title> diff --git a/include/sound/control.h b/include/sound/control.h index 4cf8f7aaa13f..ef96f07aa03b 100644 --- a/include/sound/control.h +++ b/include/sound/control.h @@ -176,12 +176,44 @@ int _snd_ctl_add_slave(struct snd_kcontrol *master, struct snd_kcontrol *slave, /* optional flags for slave */ #define SND_CTL_SLAVE_NEED_UPDATE (1 << 0) +/** + * snd_ctl_add_slave - Add a virtual slave control + * @master: vmaster element + * @slave: slave element to add + * + * Add a virtual slave control to the given master element created via + * snd_ctl_create_virtual_master() beforehand. + * Returns zero if successful or a negative error code. + * + * All slaves must be the same type (returning the same information + * via info callback). The fucntion doesn't check it, so it's your + * responsibility. + * + * Also, some additional limitations: + * at most two channels, + * logarithmic volume control (dB level) thus no linear volume, + * master can only attenuate the volume without gain + */ static inline int snd_ctl_add_slave(struct snd_kcontrol *master, struct snd_kcontrol *slave) { return _snd_ctl_add_slave(master, slave, 0); } +/** + * snd_ctl_add_slave_uncached - Add a virtual slave control + * @master: vmaster element + * @slave: slave element to add + * + * Add a virtual slave control to the given master. + * Unlike snd_ctl_add_slave(), the element added via this function + * is supposed to have volatile values, and get callback is called + * at each time quried from the master. + * + * When the control peeks the hardware values directly and the value + * can be changed by other means than the put callback of the element, + * this function should be used to keep the value always up-to-date. + */ static inline int snd_ctl_add_slave_uncached(struct snd_kcontrol *master, struct snd_kcontrol *slave) diff --git a/sound/core/vmaster.c b/sound/core/vmaster.c index d51b198d06d9..257624bd1997 100644 --- a/sound/core/vmaster.c +++ b/sound/core/vmaster.c @@ -340,8 +340,20 @@ static void master_free(struct snd_kcontrol *kcontrol) } -/* - * Create a virtual master control with the given name +/** + * snd_ctl_make_virtual_master - Create a virtual master control + * @name: name string of the control element to create + * @tlv: optional TLV int array for dB information + * + * Creates a virtual matster control with the given name string. + * Returns the created control element, or NULL for errors (ENOMEM). + * + * After creating a vmaster element, you can add the slave controls + * via snd_ctl_add_slave() or snd_ctl_add_slave_uncached(). + * + * The optional argument @tlv can be used to specify the TLV information + * for dB scale of the master control. It should be a single element + * with #SNDRV_CTL_TLVT_DB_SCALE type, and should be the max 0dB. */ struct snd_kcontrol *snd_ctl_make_virtual_master(char *name, const unsigned int *tlv) |