path: root/include/sound
diff options
authorLars-Peter Clausen <lars@metafoo.de>2015-10-18 15:39:16 +0200
committerTakashi Iwai <tiwai@suse.de>2015-10-21 14:24:14 +0200
commitbc1043cdcd84cb441d80cfd79ae4325218f6f9ba (patch)
tree3f7415ac850fc01cbf07fd0c3ad53860201306d7 /include/sound
parent7379047d5585187d1288486d4627873170d0005a (diff)
ALSA: Add helper function to add single value constraint
The recommended and most efficient way to constraint a configuration parameter to a single value is to set the minimum and maximum allowed values to the same value, i.e. calling snd_pcm_hw_constraint_minmax() with the same value for min and max. It is not necessarily obvious though that this is the approach that should be taken and some drivers have come up with other ways of solving this problem, e.g. installing a list constraint with a single item. List constraints are dynamic constraints though and hence less efficient than the static min-max constraint. This patch introduces a new helper function called snd_pcm_hw_constraint_single() which only takes a single value has the same effect as calling snd_pcm_hw_constraint_minmax() with the same values for min and max. But it is hopefully semantically more expressive, making it clear that this is the preferred way of setting a single value constraint. Signed-off-by: Lars-Peter Clausen <lars@metafoo.de> Acked-by: Mark Brown <broonie@kernel.org> Signed-off-by: Takashi Iwai <tiwai@suse.de>
Diffstat (limited to 'include/sound')
1 files changed, 16 insertions, 0 deletions
diff --git a/include/sound/pcm.h b/include/sound/pcm.h
index 691e7ee0a510..04fbcba9290b 100644
--- a/include/sound/pcm.h
+++ b/include/sound/pcm.h
@@ -1034,6 +1034,22 @@ int snd_pcm_hw_rule_add(struct snd_pcm_runtime *runtime,
snd_pcm_hw_rule_func_t func, void *private,
int dep, ...);
+ * snd_pcm_hw_constraint_single() - Constrain parameter to a single value
+ * @runtime: PCM runtime instance
+ * @var: The hw_params variable to constrain
+ * @val: The value to constrain to
+ *
+ * Return: Positive if the value is changed, zero if it's not changed, or a
+ * negative error code.
+ */
+static inline int snd_pcm_hw_constraint_single(
+ struct snd_pcm_runtime *runtime, snd_pcm_hw_param_t var,
+ unsigned int val)
+ return snd_pcm_hw_constraint_minmax(runtime, var, val, val);
int snd_pcm_format_signed(snd_pcm_format_t format);
int snd_pcm_format_unsigned(snd_pcm_format_t format);
int snd_pcm_format_linear(snd_pcm_format_t format);