ASoC: core: Support for limiting the volume

Add support for the core to limit the maximum volume on an
existing control.
The function will modify the soc_mixer_control.max value
of the given control.
The new value must be lower than the original one (chip maximum)

If there is a need for limiting a gain on a given control,
than machine drivers can do the following in their
snd_soc_dai_link.init function:

snd_soc_limit_volume(codec, "TPA6140A2 Headphone Playback Volume", 21);

This will modify the original 31 (chip maximum) to 21, so user
space will not be able to set the gain higher than this.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@nokia.com>
Acked-by: Liam Girdwood <lrg@slimlogic.co.uk>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/include/sound/soc.h b/include/sound/soc.h
index 01e9c66ddc6d..9f306f0710df 100644
--- a/include/sound/soc.h
+++ b/include/sound/soc.h
@@ -326,6 +326,8 @@ int snd_soc_get_volsw_s8(struct snd_kcontrol *kcontrol,
         struct snd_ctl_elem_value *ucontrol);
 int snd_soc_put_volsw_s8(struct snd_kcontrol *kcontrol,
         struct snd_ctl_elem_value *ucontrol);
+int snd_soc_limit_volume(struct snd_soc_codec *codec,
+        const char *name, int max);
 
 /**
  * struct snd_soc_jack_pin - Describes a pin to update based on jack detection