[PATCH v2 1/2] Add rawmidi framing API

[David Henningsson <coding@diwic.se>]

Optionally, incoming rawmidi bytes can be put inside a frame of type snd_rawmidi_framing_tstamp_t.
The main current benefit is that can enable in-kernel timestamping of incoming bytes, and that
timestamp is likely to be more precise than what userspace can offer.

Tstamp type framing requires a kernel >= 5.14 and a buffer size that is a multiple of
sizeof(snd_rawmidi_framing_tstamp_t). It is only available on input streams.

Signed-off-by: David Henningsson <coding@diwic.se>
---
 include/rawmidi.h           | 26 ++++++++++++
 include/sound/uapi/asound.h | 30 +++++++++++++-
 src/rawmidi/rawmidi.c       | 83 +++++++++++++++++++++++++++++++++++++
 src/rawmidi/rawmidi_hw.c    |  2 +
 src/rawmidi/rawmidi_local.h |  2 +
 5 files changed, 141 insertions(+), 2 deletions(-)

diff --git a/include/rawmidi.h b/include/rawmidi.h
index d88c932c..2f27cb78 100644
--- a/include/rawmidi.h
+++ b/include/rawmidi.h
@@ -79,6 +79,27 @@ typedef enum _snd_rawmidi_type {
 	SND_RAWMIDI_TYPE_VIRTUAL
 } snd_rawmidi_type_t;
 
+#define SND_RAWMIDI_CLOCK_NONE		(0<<3)
+#define SND_RAWMIDI_CLOCK_REALTIME	(1<<3)
+#define SND_RAWMIDI_CLOCK_MONOTONIC	(2<<3)
+#define SND_RAWMIDI_CLOCK_MONOTONIC_RAW	(3<<3)
+
+#define SND_RAWMIDI_FRAMING_DATA_LENGTH 16
+
+/** Incoming RawMidi bytes is put inside this container if tstamp type framing is enabled. */
+typedef struct _snd_rawmidi_framing_tstamp {
+	/**
+	 * For now, frame_type is always 0. Midi 2.0 is expected to add new
+	 * types here. Applications are expected to skip unknown frame types.
+	 */
+	__u8 frame_type;
+	__u8 length; /* number of valid bytes in data field */
+	__u8 reserved[2];
+	__u32 tv_nsec;		/* nanoseconds */
+	__u64 tv_sec;		/* seconds */
+	__u8 data[SND_RAWMIDI_FRAMING_DATA_LENGTH];
+} snd_rawmidi_framing_tstamp_t;
+
 int snd_rawmidi_open(snd_rawmidi_t **in_rmidi, snd_rawmidi_t **out_rmidi,
 		     const char *name, int mode);
 int snd_rawmidi_open_lconf(snd_rawmidi_t **in_rmidi, snd_rawmidi_t **out_rmidi,
@@ -126,6 +147,11 @@ int snd_rawmidi_params_set_avail_min(snd_rawmidi_t *rmidi, snd_rawmidi_params_t
 size_t snd_rawmidi_params_get_avail_min(const snd_rawmidi_params_t *params);
 int snd_rawmidi_params_set_no_active_sensing(snd_rawmidi_t *rmidi, snd_rawmidi_params_t *params, int val);
 int snd_rawmidi_params_get_no_active_sensing(const snd_rawmidi_params_t *params);
+int snd_rawmidi_params_set_framing_type(const snd_rawmidi_t *rawmidi, snd_rawmidi_params_t *params, unsigned int val);
+int snd_rawmidi_params_get_framing_type(const snd_rawmidi_params_t *params);
+int snd_rawmidi_params_set_clock_type(const snd_rawmidi_t *rawmidi, snd_rawmidi_params_t *params, unsigned int val);
+int snd_rawmidi_params_get_clock_type(const snd_rawmidi_params_t *params);
+
 int snd_rawmidi_params(snd_rawmidi_t *rmidi, snd_rawmidi_params_t * params);
 int snd_rawmidi_params_current(snd_rawmidi_t *rmidi, snd_rawmidi_params_t *params);
 size_t snd_rawmidi_status_sizeof(void);
diff --git a/include/sound/uapi/asound.h b/include/sound/uapi/asound.h
index ec610c27..9fe3943f 100644
--- a/include/sound/uapi/asound.h
+++ b/include/sound/uapi/asound.h
@@ -702,7 +702,7 @@ enum {
  *  Raw MIDI section - /dev/snd/midi??
  */
 
-#define SNDRV_RAWMIDI_VERSION		SNDRV_PROTOCOL_VERSION(2, 0, 1)
+#define SNDRV_RAWMIDI_VERSION		SNDRV_PROTOCOL_VERSION(2, 0, 2)
 
 enum {
 	SNDRV_RAWMIDI_STREAM_OUTPUT = 0,
@@ -728,12 +728,38 @@ struct snd_rawmidi_info {
 	unsigned char reserved[64];	/* reserved for future use */
 };
 
+#define SNDRV_RAWMIDI_MODE_FRAMING_MASK		(7<<0)
+#define SNDRV_RAWMIDI_MODE_FRAMING_SHIFT	0
+#define SNDRV_RAWMIDI_MODE_FRAMING_NONE		(0<<0)
+#define SNDRV_RAWMIDI_MODE_FRAMING_TSTAMP	(1<<0)
+#define SNDRV_RAWMIDI_MODE_CLOCK_MASK		(7<<3)
+#define SNDRV_RAWMIDI_MODE_CLOCK_SHIFT		3
+#define SNDRV_RAWMIDI_MODE_CLOCK_NONE		(0<<3)
+#define SNDRV_RAWMIDI_MODE_CLOCK_REALTIME	(1<<3)
+#define SNDRV_RAWMIDI_MODE_CLOCK_MONOTONIC	(2<<3)
+#define SNDRV_RAWMIDI_MODE_CLOCK_MONOTONIC_RAW	(3<<3)
+
+#define SNDRV_RAWMIDI_FRAMING_DATA_LENGTH 16
+
+struct snd_rawmidi_framing_tstamp {
+	/* For now, frame_type is always 0. Midi 2.0 is expected to add new
+	 * types here. Applications are expected to skip unknown frame types.
+	 */
+	__u8 frame_type;
+	__u8 length; /* number of valid bytes in data field */
+	__u8 reserved[2];
+	__u32 tv_nsec;		/* nanoseconds */
+	__u64 tv_sec;		/* seconds */
+	__u8 data[SNDRV_RAWMIDI_FRAMING_DATA_LENGTH];
+} __packed;
+
 struct snd_rawmidi_params {
 	int stream;
 	size_t buffer_size;		/* queue size in bytes */
 	size_t avail_min;		/* minimum avail bytes for wakeup */
 	unsigned int no_active_sensing: 1; /* do not send active sensing byte in close() */
-	unsigned char reserved[16];	/* reserved for future use */
+	unsigned int mode;		/* For input data only, frame incoming data */
+	unsigned char reserved[12];	/* reserved for future use */
 };
 
 struct snd_rawmidi_status {
diff --git a/src/rawmidi/rawmidi.c b/src/rawmidi/rawmidi.c
index 55f44821..8ca7a8ac 100644
--- a/src/rawmidi/rawmidi.c
+++ b/src/rawmidi/rawmidi.c
@@ -118,6 +118,15 @@ hw:soundwave,1,2
 hw:DEV=1,CARD=soundwave,SUBDEV=2
 \endcode
 
+\section rawmidi_framing Framing of rawmidi data
+
+Optionally, incoming rawmidi bytes can be put inside a frame of type snd_rawmidi_framing_tstamp_t.
+The main current benefit is that can enable in-kernel timestamping of incoming bytes, and that
+timestamp is likely to be more precise than what userspace can offer.
+
+Tstamp type framing requires a kernel >= 5.14 and a buffer size that is a multiple of
+sizeof(snd_rawmidi_framing_tstamp_t). It is only available on input streams.
+
 \section rawmidi_examples Examples
 
 The full featured examples with cross-links:
@@ -154,6 +163,7 @@ static int snd_rawmidi_params_default(snd_rawmidi_t *rawmidi, snd_rawmidi_params
 	params->buffer_size = page_size();
 	params->avail_min = 1;
 	params->no_active_sensing = 1;
+	params->mode = 0;
 	return 0;
 }
 
@@ -811,6 +821,77 @@ int snd_rawmidi_params_get_no_active_sensing(const snd_rawmidi_params_t *params)
 	return params->no_active_sensing;
 }
 
+/**
+ * \brief enable or disable rawmidi framing
+ * \param rawmidi RawMidi handle
+ * \param params pointer to snd_rawmidi_params_t structure
+ * \param val (0 = no framing, 1 = tstamp type framing)
+ * \return 0 on success, otherwise a negative error code.
+ *
+ * Notable error codes:
+ * -EINVAL - "val" is invalid
+ * -ENOTSUP - Kernel is too old to support framing.
+ *
+ */
+int snd_rawmidi_params_set_framing_type(const snd_rawmidi_t *rawmidi, snd_rawmidi_params_t *params, unsigned int val)
+{
+	assert(rawmidi && params);
+	if (val > SNDRV_RAWMIDI_MODE_FRAMING_MASK >> SNDRV_RAWMIDI_MODE_FRAMING_SHIFT)
+		return -EINVAL;
+	if (val != SNDRV_RAWMIDI_MODE_FRAMING_NONE &&
+		(rawmidi->version < SNDRV_PROTOCOL_VERSION(2, 0, 2) || rawmidi->stream != SND_RAWMIDI_STREAM_INPUT))
+		return -ENOTSUP;
+	params->mode = (params->mode & ~SNDRV_RAWMIDI_MODE_FRAMING_MASK) + (val << SNDRV_RAWMIDI_MODE_FRAMING_SHIFT);
+	return 0;
+}
+
+/**
+ * \brief get current framing type
+ * \param params pointer to snd_rawmidi_params_t structure
+ * \return the current type (0 = no framing, 1 = tstamp type framing)
+ */
+int snd_rawmidi_params_get_framing_type(const snd_rawmidi_params_t *params)
+{
+	assert(params);
+	return (params->mode & SNDRV_RAWMIDI_MODE_FRAMING_MASK) >> SNDRV_RAWMIDI_MODE_FRAMING_SHIFT;
+}
+
+/**
+ * \brief sets clock type for tstamp type framing
+ * \param rawmidi RawMidi handle
+ * \param params pointer to snd_rawmidi_params_t structure
+ * \param val one of the SND_RAWMIDI_CLOCK_* constants
+ * \return 0 on success, otherwise a negative error code.
+ *
+ * Notable error codes:
+ * -EINVAL - "val" is invalid
+ * -ENOTSUP - Kernel is too old to support framing.
+ *
+ */
+int snd_rawmidi_params_set_clock_type(const snd_rawmidi_t *rawmidi, snd_rawmidi_params_t *params, unsigned int val)
+{
+	assert(rawmidi && params);
+	if (val > SNDRV_RAWMIDI_MODE_CLOCK_MASK >> SNDRV_RAWMIDI_MODE_CLOCK_SHIFT)
+		return -EINVAL;
+	if (val != SNDRV_RAWMIDI_MODE_CLOCK_NONE &&
+		(rawmidi->version < SNDRV_PROTOCOL_VERSION(2, 0, 2) || rawmidi->stream != SND_RAWMIDI_STREAM_INPUT))
+		return -ENOTSUP;
+	params->mode = (params->mode & ~SNDRV_RAWMIDI_MODE_CLOCK_MASK) + (val << SNDRV_RAWMIDI_MODE_CLOCK_SHIFT);
+	return 0;
+}
+
+/**
+ * \brief get current clock type (for tstamp type framing)
+ * \param params pointer to snd_rawmidi_params_t structure
+ * \return the current clock type (one of the SND_RAWMIDI_CLOCK_* constants)
+ */
+int snd_rawmidi_params_get_clock_type(const snd_rawmidi_params_t *params)
+{
+	assert(params);
+	return (params->mode & SNDRV_RAWMIDI_MODE_CLOCK_MASK) >> SNDRV_RAWMIDI_MODE_CLOCK_SHIFT;
+}
+
+
 /**
  * \brief set parameters about rawmidi stream
  * \param rawmidi RawMidi handle
@@ -828,6 +909,7 @@ int snd_rawmidi_params(snd_rawmidi_t *rawmidi, snd_rawmidi_params_t * params)
 	rawmidi->buffer_size = params->buffer_size;
 	rawmidi->avail_min = params->avail_min;
 	rawmidi->no_active_sensing = params->no_active_sensing;
+	rawmidi->params_mode = rawmidi->version < SNDRV_PROTOCOL_VERSION(2, 0, 2) ? 0 : params->mode;
 	return 0;
 }
 
@@ -844,6 +926,7 @@ int snd_rawmidi_params_current(snd_rawmidi_t *rawmidi, snd_rawmidi_params_t *par
 	params->buffer_size = rawmidi->buffer_size;
 	params->avail_min = rawmidi->avail_min;
 	params->no_active_sensing = rawmidi->no_active_sensing;
+	params->mode = rawmidi->params_mode;
 	return 0;
 }
 
diff --git a/src/rawmidi/rawmidi_hw.c b/src/rawmidi/rawmidi_hw.c
index 99927d75..6bfbc1f3 100644
--- a/src/rawmidi/rawmidi_hw.c
+++ b/src/rawmidi/rawmidi_hw.c
@@ -285,6 +285,7 @@ int snd_rawmidi_hw_open(snd_rawmidi_t **inputp, snd_rawmidi_t **outputp,
 		rmidi->poll_fd = fd;
 		rmidi->ops = &snd_rawmidi_hw_ops;
 		rmidi->private_data = hw;
+		rmidi->version = ver;
 		hw->open++;
 		*inputp = rmidi;
 	}
@@ -300,6 +301,7 @@ int snd_rawmidi_hw_open(snd_rawmidi_t **inputp, snd_rawmidi_t **outputp,
 		rmidi->poll_fd = fd;
 		rmidi->ops = &snd_rawmidi_hw_ops;
 		rmidi->private_data = hw;
+		rmidi->version = ver;
 		hw->open++;
 		*outputp = rmidi;
 	}
diff --git a/src/rawmidi/rawmidi_local.h b/src/rawmidi/rawmidi_local.h
index 721e1ec9..c4068d7c 100644
--- a/src/rawmidi/rawmidi_local.h
+++ b/src/rawmidi/rawmidi_local.h
@@ -42,12 +42,14 @@ struct _snd_rawmidi {
 	snd_rawmidi_type_t type;
 	snd_rawmidi_stream_t stream;
 	int mode;
+	int version;
 	int poll_fd;
 	const snd_rawmidi_ops_t *ops;
 	void *private_data;
 	size_t buffer_size;
 	size_t avail_min;
 	unsigned int no_active_sensing: 1;
+	int params_mode;
 };
 
 int snd_rawmidi_hw_open(snd_rawmidi_t **input, snd_rawmidi_t **output,
-- 
2.25.1