[RFC PATCH 01/17] ALSA: pcm: Introduce MSBITS subformat interface

[Cezary Rojewski <cezary.rojewski@intel.com>]

Improve granularity of format selection for S32/U32 formats by adding
constants representing 20, 24 and 32 most significant bits.

To make it easy for drivers to utilize those constants, introduce
snd_pcm_subformat_width() and params_bps(). While the former is
self-explanatory, the latter returns the bit-per-sample value based on
format, subformat and msbits characteristics of the provided hw_params.

Signed-off-by: Cezary Rojewski <cezary.rojewski@intel.com>
---
 include/sound/pcm.h               |  8 ++++++++
 include/sound/pcm_params.h        |  2 ++
 include/uapi/sound/asound.h       |  5 ++++-
 sound/core/pcm_lib.c              | 30 ++++++++++++++++++++++++++++++
 sound/core/pcm_misc.c             | 23 +++++++++++++++++++++++
 tools/include/uapi/sound/asound.h |  5 ++++-
 6 files changed, 71 insertions(+), 2 deletions(-)

diff --git a/include/sound/pcm.h b/include/sound/pcm.h
index 19f564606ac4..f78441ff9d85 100644
--- a/include/sound/pcm.h
+++ b/include/sound/pcm.h
@@ -31,6 +31,7 @@
 struct snd_pcm_hardware {
 	unsigned int info;		/* SNDRV_PCM_INFO_* */
 	u64 formats;			/* SNDRV_PCM_FMTBIT_* */
+	u64 subformats;			/* SNDRV_PCM_SUBFMTBIT_* */
 	unsigned int rates;		/* SNDRV_PCM_RATE_* */
 	unsigned int rate_min;		/* min rate */
 	unsigned int rate_max;		/* max rate */
@@ -219,6 +220,12 @@ struct snd_pcm_ops {
 #define SNDRV_PCM_FMTBIT_U20		SNDRV_PCM_FMTBIT_U20_BE
 #endif
 
+#define _SNDRV_PCM_SUBFMTBIT(fmt)	BIT((__force int)SNDRV_PCM_SUBFORMAT_##fmt)
+#define SNDRV_PCM_SUBFMTBIT_STD		_SNDRV_PCM_SUBFMTBIT(STD)
+#define SNDRV_PCM_SUBFMTBIT_MSBITS_20	_SNDRV_PCM_SUBFMTBIT(MSBITS_20)
+#define SNDRV_PCM_SUBFMTBIT_MSBITS_24	_SNDRV_PCM_SUBFMTBIT(MSBITS_24)
+#define SNDRV_PCM_SUBFMTBIT_MSBITS_32	_SNDRV_PCM_SUBFMTBIT(MSBITS_32)
+
 struct snd_pcm_file {
 	struct snd_pcm_substream *substream;
 	int no_compat_mmap;
@@ -1130,6 +1137,7 @@ int snd_pcm_format_physical_width(snd_pcm_format_t format);		/* in bits */
 ssize_t snd_pcm_format_size(snd_pcm_format_t format, size_t samples);
 const unsigned char *snd_pcm_format_silence_64(snd_pcm_format_t format);
 int snd_pcm_format_set_silence(snd_pcm_format_t format, void *buf, unsigned int frames);
+int snd_pcm_subformat_width(snd_pcm_subformat_t subformat);
 
 void snd_pcm_set_ops(struct snd_pcm * pcm, int direction,
 		     const struct snd_pcm_ops *ops);
diff --git a/include/sound/pcm_params.h b/include/sound/pcm_params.h
index ba184f49f7e1..f09ae37ed44d 100644
--- a/include/sound/pcm_params.h
+++ b/include/sound/pcm_params.h
@@ -362,6 +362,8 @@ static inline int params_physical_width(const struct snd_pcm_hw_params *p)
 	return snd_pcm_format_physical_width(params_format(p));
 }
 
+int params_bps(const struct snd_pcm_hw_params *p);
+
 static inline void
 params_set_format(struct snd_pcm_hw_params *p, snd_pcm_format_t fmt)
 {
diff --git a/include/uapi/sound/asound.h b/include/uapi/sound/asound.h
index d6864f672630..27db9f3558fd 100644
--- a/include/uapi/sound/asound.h
+++ b/include/uapi/sound/asound.h
@@ -268,7 +268,10 @@ typedef int __bitwise snd_pcm_format_t;
 
 typedef int __bitwise snd_pcm_subformat_t;
 #define	SNDRV_PCM_SUBFORMAT_STD		((__force snd_pcm_subformat_t) 0)
-#define	SNDRV_PCM_SUBFORMAT_LAST	SNDRV_PCM_SUBFORMAT_STD
+#define	SNDRV_PCM_SUBFORMAT_MSBITS_20	((__force snd_pcm_subformat_t) 1)
+#define	SNDRV_PCM_SUBFORMAT_MSBITS_24	((__force snd_pcm_subformat_t) 2)
+#define	SNDRV_PCM_SUBFORMAT_MSBITS_32	((__force snd_pcm_subformat_t) 3)
+#define	SNDRV_PCM_SUBFORMAT_LAST	SNDRV_PCM_SUBFORMAT_MSBITS_32
 
 #define SNDRV_PCM_INFO_MMAP		0x00000001	/* hardware supports mmap */
 #define SNDRV_PCM_INFO_MMAP_VALID	0x00000002	/* period data are valid during transfer */
diff --git a/sound/core/pcm_lib.c b/sound/core/pcm_lib.c
index 9c121a921b04..4a60632220c2 100644
--- a/sound/core/pcm_lib.c
+++ b/sound/core/pcm_lib.c
@@ -1706,6 +1706,36 @@ int snd_pcm_hw_param_last(struct snd_pcm_substream *pcm,
 }
 EXPORT_SYMBOL(snd_pcm_hw_param_last);
 
+/**
+ * params_bps - Get the number of bits per the sample.
+ * @p: hardware parameters
+ *
+ * Return: The number of bits per sample based on the format,
+ * subformat and msbits the specified hw params has.
+ */
+int params_bps(const struct snd_pcm_hw_params *p)
+{
+	snd_pcm_subformat_t subformat = params_subformat(p);
+	snd_pcm_format_t format = params_format(p);
+	int width;
+
+	switch (format) {
+	case SNDRV_PCM_FORMAT_S32_LE:
+	case SNDRV_PCM_FORMAT_U32_LE:
+	case SNDRV_PCM_FORMAT_S32_BE:
+	case SNDRV_PCM_FORMAT_U32_BE:
+		width = snd_pcm_subformat_width(subformat);
+		if (width)
+			return width;
+		if (p->msbits)
+			return (int)p->msbits;
+		fallthrough;
+	default:
+		return snd_pcm_format_width(format);
+	}
+}
+EXPORT_SYMBOL(params_bps);
+
 static int snd_pcm_lib_ioctl_reset(struct snd_pcm_substream *substream,
 				   void *arg)
 {
diff --git a/sound/core/pcm_misc.c b/sound/core/pcm_misc.c
index 5588b6a1ee8b..127bb36fd2e4 100644
--- a/sound/core/pcm_misc.c
+++ b/sound/core/pcm_misc.c
@@ -482,6 +482,29 @@ int snd_pcm_format_set_silence(snd_pcm_format_t format, void *data, unsigned int
 }
 EXPORT_SYMBOL(snd_pcm_format_set_silence);
 
+/**
+ * snd_pcm_subformat_width - return the bit-width of the subformat
+ * @subformat: the subformat to check
+ *
+ * Return: The bit-width of the subformat, or a negative error code
+ * otherwise.
+ */
+int snd_pcm_subformat_width(snd_pcm_subformat_t subformat)
+{
+	switch (subformat) {
+	case SNDRV_PCM_SUBFORMAT_MSBITS_20:
+		return 20;
+	case SNDRV_PCM_SUBFORMAT_MSBITS_24:
+		return 24;
+	case SNDRV_PCM_SUBFORMAT_MSBITS_32:
+		return 32;
+	case SNDRV_PCM_SUBFORMAT_STD:
+	default:
+		return 0;
+	}
+}
+EXPORT_SYMBOL(snd_pcm_subformat_width);
+
 /**
  * snd_pcm_hw_limit_rates - determine rate_min/rate_max fields
  * @hw: the pcm hw instance
diff --git a/tools/include/uapi/sound/asound.h b/tools/include/uapi/sound/asound.h
index 0aa955aa8246..eb45a698767f 100644
--- a/tools/include/uapi/sound/asound.h
+++ b/tools/include/uapi/sound/asound.h
@@ -267,7 +267,10 @@ typedef int __bitwise snd_pcm_format_t;
 
 typedef int __bitwise snd_pcm_subformat_t;
 #define	SNDRV_PCM_SUBFORMAT_STD		((__force snd_pcm_subformat_t) 0)
-#define	SNDRV_PCM_SUBFORMAT_LAST	SNDRV_PCM_SUBFORMAT_STD
+#define	SNDRV_PCM_SUBFORMAT_MSBITS_20	((__force snd_pcm_subformat_t) 1)
+#define	SNDRV_PCM_SUBFORMAT_MSBITS_24	((__force snd_pcm_subformat_t) 2)
+#define	SNDRV_PCM_SUBFORMAT_MSBITS_32	((__force snd_pcm_subformat_t) 3)
+#define	SNDRV_PCM_SUBFORMAT_LAST	SNDRV_PCM_SUBFORMAT_MSBITS_32
 
 #define SNDRV_PCM_INFO_MMAP		0x00000001	/* hardware supports mmap */
 #define SNDRV_PCM_INFO_MMAP_VALID	0x00000002	/* period data are valid during transfer */
-- 
2.25.1