ALSA: pcm: Introduce MSBITS subformat interface

Improve granularity of format selection for S32/U32 formats by adding
constants representing 20, 24 and MAX most significant bits.

The MAX means the maximum number of significant bits which can
the physical format hold. For 32-bit formats, MAX is related
to 32 bits. For 8-bit formats, MAX is related to 8 bits etc.

As there is only one user currently (format S32_LE), subformat is
represented by a simple u32 and stores flags only for that one user
alone. The approach of subformat being part of struct snd_pcm_hardware
is a compromise between ALSA and ASoC allowing for
hw_params-intersection code to be alloc/free-less while not adding any
new responsibilities to ASoC runtime structures.

Acked-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Jaroslav Kysela <perex@perex.cz>
Co-developed-by: Cezary Rojewski <cezary.rojewski@intel.com>
Signed-off-by: Cezary Rojewski <cezary.rojewski@intel.com>
Link: https://lore.kernel.org/r/20231117120610.1755254-2-cezary.rojewski@intel.com
Signed-off-by: Takashi Iwai <tiwai@suse.de>

2 files changed, 56 insertions, 2 deletions

diff --git a/sound/core/pcm.c b/sound/core/pcm.c
index 20bb2d7c8d4b..c4bc15f048b6 100644
--- a/sound/core/pcm.c
+++ b/sound/core/pcm.c
@@ -265,6 +265,9 @@ static const char * const snd_pcm_access_names[] = {
 
 static const char * const snd_pcm_subformat_names[] = {
 	SUBFORMAT(STD), 
+	SUBFORMAT(MSBITS_MAX),
+	SUBFORMAT(MSBITS_20),
+	SUBFORMAT(MSBITS_24),
 };
 
 static const char * const snd_pcm_tstamp_mode_names[] = {
diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c
index f610b08f5a2b..f5ff00f99788 100644
--- a/sound/core/pcm_native.c
+++ b/sound/core/pcm_native.c
@@ -479,6 +479,7 @@ static int fixup_unreferenced_params(struct snd_pcm_substream *substream,
 {
 	const struct snd_interval *i;
 	const struct snd_mask *m;
+	struct snd_mask *m_rw;
 	int err;
 
 	if (!params->msbits) {
@@ -487,6 +488,22 @@ static int fixup_unreferenced_params(struct snd_pcm_substream *substream,
 			params->msbits = snd_interval_value(i);
 	}
 
+	if (params->msbits) {
+		m = hw_param_mask_c(params, SNDRV_PCM_HW_PARAM_FORMAT);
+		if (snd_mask_single(m)) {
+			snd_pcm_format_t format = (__force snd_pcm_format_t)snd_mask_min(m);
+
+			if (snd_pcm_format_linear(format) &&
+			    snd_pcm_format_width(format) != params->msbits) {
+				m_rw = hw_param_mask(params, SNDRV_PCM_HW_PARAM_SUBFORMAT);
+				snd_mask_reset(m_rw,
+					       (__force unsigned)SNDRV_PCM_SUBFORMAT_MSBITS_MAX);
+				if (snd_mask_empty(m_rw))
+					return -EINVAL;
+			}
+		}
+	}
+
 	if (!params->rate_den) {
 		i = hw_param_interval_c(params, SNDRV_PCM_HW_PARAM_RATE);
 		if (snd_interval_single(i)) {
@@ -2483,6 +2500,41 @@ static int snd_pcm_hw_rule_buffer_bytes_max(struct snd_pcm_hw_params *params,
 	return snd_interval_refine(hw_param_interval(params, rule->var), &t);
 }		
 
+static int snd_pcm_hw_rule_subformats(struct snd_pcm_hw_params *params,
+				      struct snd_pcm_hw_rule *rule)
+{
+	struct snd_mask *sfmask = hw_param_mask(params, SNDRV_PCM_HW_PARAM_SUBFORMAT);
+	struct snd_mask *fmask = hw_param_mask(params, SNDRV_PCM_HW_PARAM_FORMAT);
+	u32 *subformats = rule->private;
+	snd_pcm_format_t f;
+	struct snd_mask m;
+
+	snd_mask_none(&m);
+	/* All PCMs support at least the default STD subformat. */
+	snd_mask_set(&m, (__force unsigned)SNDRV_PCM_SUBFORMAT_STD);
+
+	pcm_for_each_format(f) {
+		if (!snd_mask_test(fmask, (__force unsigned)f))
+			continue;
+
+		if (f == SNDRV_PCM_FORMAT_S32_LE && *subformats)
+			m.bits[0] |= *subformats;
+		else if (snd_pcm_format_linear(f))
+			snd_mask_set(&m, (__force unsigned)SNDRV_PCM_SUBFORMAT_MSBITS_MAX);
+	}
+
+	return snd_mask_refine(sfmask, &m);
+}
+
+static int snd_pcm_hw_constraint_subformats(struct snd_pcm_runtime *runtime,
+					   unsigned int cond, u32 *subformats)
+{
+	return snd_pcm_hw_rule_add(runtime, cond, -1,
+				   snd_pcm_hw_rule_subformats, (void *)subformats,
+				   SNDRV_PCM_HW_PARAM_SUBFORMAT,
+				   SNDRV_PCM_HW_PARAM_FORMAT, -1);
+}
+
 static int snd_pcm_hw_constraints_init(struct snd_pcm_substream *substream)
 {
 	struct snd_pcm_runtime *runtime = substream->runtime;
@@ -2634,8 +2686,7 @@ static int snd_pcm_hw_constraints_complete(struct snd_pcm_substream *substream)
 	if (err < 0)
 		return err;
 
-	err = snd_pcm_hw_constraint_mask(runtime, SNDRV_PCM_HW_PARAM_SUBFORMAT,
-					 PARAM_MASK_BIT(SNDRV_PCM_SUBFORMAT_STD));
+	err = snd_pcm_hw_constraint_subformats(runtime, 0, &hw->subformats);
 	if (err < 0)
 		return err;