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[1/8] ALSA: rawmidi: Expose the tied device number in info ioctl

Message ID 20250110155943.31578-2-tiwai@suse.de (mailing list archive)
State New
Headers show
Series ALSA: Small extensions for UMP | expand

Commit Message

Takashi Iwai Jan. 10, 2025, 3:59 p.m. UTC 
The UMP legacy rawmidi is derived from the UMP rawmidi, but currently
there is no way to know which device is involved in other side.

This patch extends the rawmidi info ioctl to show the tied device
number.  As default it stores -1, indicating that no tied device.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
---
 Documentation/sound/designs/midi-2.0.rst | 5 +++++
 include/sound/rawmidi.h                  | 1 +
 include/uapi/sound/asound.h              | 5 ++++-
 sound/core/rawmidi.c                     | 2 ++
 sound/core/ump.c                         | 3 +++
 5 files changed, 15 insertions(+), 1 deletion(-)

Comments

Jaroslav Kysela Jan. 14, 2025, 10:25 a.m. UTC | #1 
On 10. 01. 25 16:59, Takashi Iwai wrote:
> The UMP legacy rawmidi is derived from the UMP rawmidi, but currently
> there is no way to know which device is involved in other side.
> 
> This patch extends the rawmidi info ioctl to show the tied device
> number.  As default it stores -1, indicating that no tied device.

Seeing the alsa-lib changes, it may be probably better to keep zero as unknown 
and define this field as (device number + 1) to avoid bad interpretation for 
older kernels without protocol version checks.

					Jaroslav
Takashi Iwai Jan. 14, 2025, 10:37 a.m. UTC | #2 
On Tue, 14 Jan 2025 11:25:05 +0100,
Jaroslav Kysela wrote:
> 
> On 10. 01. 25 16:59, Takashi Iwai wrote:
> > The UMP legacy rawmidi is derived from the UMP rawmidi, but currently
> > there is no way to know which device is involved in other side.
> > 
> > This patch extends the rawmidi info ioctl to show the tied device
> > number.  As default it stores -1, indicating that no tied device.
> 
> Seeing the alsa-lib changes, it may be probably better to keep zero as
> unknown and define this field as (device number + 1) to avoid bad
> interpretation for older kernels without protocol version checks.

It might be safer, yes, although it'd need an extra interpretation.
But maybe the safety should win.

OK, I'll submit the patch to update it before 6.14.


thanks,

Takashi
diff mbox series

Patch

diff --git a/Documentation/sound/designs/midi-2.0.rst b/Documentation/sound/designs/midi-2.0.rst
index 086487ca7ab1..d525bc2805f7 100644
--- a/Documentation/sound/designs/midi-2.0.rst
+++ b/Documentation/sound/designs/midi-2.0.rst
@@ -293,6 +293,11 @@  Rawmidi API Extensions
   status 0x05).  When UMP core receives such a message, it updates the
   UMP EP info and the corresponding sequencer clients as well.
 
+* The legacy rawmidi device number is found in the new `tied_device`
+  field of the rawmidi info.
+  On the other hand, the UMP rawmidi device number is found in
+  `tied_device` field of the legacy rawmidi info, too.
+
 
 Control API Extensions
 ======================
diff --git a/include/sound/rawmidi.h b/include/sound/rawmidi.h
index f31cabf0158c..7f1fec786b72 100644
--- a/include/sound/rawmidi.h
+++ b/include/sound/rawmidi.h
@@ -118,6 +118,7 @@  struct snd_rawmidi {
 	struct list_head list;
 	unsigned int device;		/* device number */
 	unsigned int info_flags;	/* SNDRV_RAWMIDI_INFO_XXXX */
+	unsigned int tied_device;
 	char id[64];
 	char name[80];
 
diff --git a/include/uapi/sound/asound.h b/include/uapi/sound/asound.h
index 4cd513215bcd..1fcff031b5e3 100644
--- a/include/uapi/sound/asound.h
+++ b/include/uapi/sound/asound.h
@@ -729,6 +729,8 @@  enum {
 #define SNDRV_RAWMIDI_INFO_DUPLEX		0x00000004
 #define SNDRV_RAWMIDI_INFO_UMP			0x00000008
 
+#define SNDRV_RAWMIDI_DEVICE_UNKNOWN		-1
+
 struct snd_rawmidi_info {
 	unsigned int device;		/* RO/WR (control): device number */
 	unsigned int subdevice;		/* RO/WR (control): subdevice number */
@@ -740,7 +742,8 @@  struct snd_rawmidi_info {
 	unsigned char subname[32];	/* name of active or selected subdevice */
 	unsigned int subdevices_count;
 	unsigned int subdevices_avail;
-	unsigned char reserved[64];	/* reserved for future use */
+	int tied_device;		/* R: tied rawmidi device (UMP/legacy) */
+	unsigned char reserved[60];	/* reserved for future use */
 };
 
 #define SNDRV_RAWMIDI_MODE_FRAMING_MASK		(7<<0)
diff --git a/sound/core/rawmidi.c b/sound/core/rawmidi.c
index 348ce1b7725e..858878fe487a 100644
--- a/sound/core/rawmidi.c
+++ b/sound/core/rawmidi.c
@@ -635,6 +635,7 @@  static int snd_rawmidi_info(struct snd_rawmidi_substream *substream,
 	info->subdevices_count = substream->pstr->substream_count;
 	info->subdevices_avail = (substream->pstr->substream_count -
 				  substream->pstr->substream_opened);
+	info->tied_device = rmidi->tied_device;
 	return 0;
 }
 
@@ -1834,6 +1835,7 @@  int snd_rawmidi_init(struct snd_rawmidi *rmidi,
 	INIT_LIST_HEAD(&rmidi->streams[SNDRV_RAWMIDI_STREAM_INPUT].substreams);
 	INIT_LIST_HEAD(&rmidi->streams[SNDRV_RAWMIDI_STREAM_OUTPUT].substreams);
 	rmidi->info_flags = info_flags;
+	rmidi->tied_device = SNDRV_RAWMIDI_DEVICE_UNKNOWN;
 
 	if (id != NULL)
 		strscpy(rmidi->id, id, sizeof(rmidi->id));
diff --git a/sound/core/ump.c b/sound/core/ump.c
index 9198bff4768c..0bfab84eaafb 100644
--- a/sound/core/ump.c
+++ b/sound/core/ump.c
@@ -1314,6 +1314,9 @@  int snd_ump_attach_legacy_rawmidi(struct snd_ump_endpoint *ump,
 	ump->legacy_rmidi = rmidi;
 	update_legacy_names(ump);
 
+	rmidi->tied_device = ump->core.device;
+	ump->core.tied_device = rmidi->device;
+
 	ump_dbg(ump, "Created a legacy rawmidi #%d (%s)\n", device, id);
 	return 0;
 }