ALSA: pcm: add snd_pcm_hw_rule_noresample()

Add a helper function to allow drivers to disable hardware resampling
when the application has specified the SNDRV_PCM_HW_PARAMS_NORESAMPLE
flag.

Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

1 files changed, 26 insertions, 0 deletions

diff --git a/sound/core/pcm_lib.c b/sound/core/pcm_lib.c
index 62e90b862a0..95d1e789715 100644
--- a/sound/core/pcm_lib.c
+++ b/sound/core/pcm_lib.c
@@ -1399,6 +1399,32 @@ int snd_pcm_hw_constraint_pow2(struct snd_pcm_runtime *runtime,
 
 EXPORT_SYMBOL(snd_pcm_hw_constraint_pow2);
 
+static int snd_pcm_hw_rule_noresample_func(struct snd_pcm_hw_params *params,
+                                           struct snd_pcm_hw_rule *rule)
+{
+        unsigned int base_rate = (unsigned int)(uintptr_t)rule->private;
+        struct snd_interval *rate;
+
+        rate = hw_param_interval(params, SNDRV_PCM_HW_PARAM_RATE);
+        return snd_interval_list(rate, 1, &base_rate, 0);
+}
+
+/**
+ * snd_pcm_hw_rule_noresample - add a rule to allow disabling hw resampling
+ * @runtime: PCM runtime instance
+ * @base_rate: the rate at which the hardware does not resample
+ */
+int snd_pcm_hw_rule_noresample(struct snd_pcm_runtime *runtime,
+                               unsigned int base_rate)
+{
+        return snd_pcm_hw_rule_add(runtime, SNDRV_PCM_HW_PARAMS_NORESAMPLE,
+                                   SNDRV_PCM_HW_PARAM_RATE,
+                                   snd_pcm_hw_rule_noresample_func,
+                                   (void *)(uintptr_t)base_rate,
+                                   SNDRV_PCM_HW_PARAM_RATE, -1);
+}
+EXPORT_SYMBOL(snd_pcm_hw_rule_noresample);
+
 static void _snd_pcm_hw_param_any(struct snd_pcm_hw_params *params,
                                   snd_pcm_hw_param_t var)
 {