ALSA: usb-audio: generate midi streaming substream names from jack names

A number of devices have named substreams which are hard to remember /
decypher from <device> MIDI n names. Eg. Korg puts a pass through on
one substream and iConnectivity devices name the connections.

This makes it easier to connect to the correct device.  Devices which
handle naming through quirks are unaffected by this change.

Addresses TODO comment in sound/usb/midi.c
Signed-off-by: George Harker <george@george-graphics.co.uk>
Link: https://lore.kernel.org/r/20210226212617.24616-1-george@george-graphics.co.ukSigned-off-by: Takashi Iwai <tiwai@suse.de>

sound/usb/midi.c

@@ -1740,12 +1740,68 @@ static void snd_usbmidi_get_port_info(struct snd_rawmidi *rmidi, int number,
 	}
 }
 
+static struct usb_midi_in_jack_descriptor *find_usb_in_jack_descriptor(
+					struct usb_host_interface *hostif, uint8_t jack_id)
+{
+	unsigned char *extra = hostif->extra;
+	int extralen = hostif->extralen;
+
+	while (extralen > 4) {
+		struct usb_midi_in_jack_descriptor *injd =
+				(struct usb_midi_in_jack_descriptor *)extra;
+
+		if (injd->bLength > 4 &&
+		    injd->bDescriptorType == USB_DT_CS_INTERFACE &&
+		    injd->bDescriptorSubtype == UAC_MIDI_IN_JACK &&
+				injd->bJackID == jack_id)
+			return injd;
+		if (!extra[0])
+			break;
+		extralen -= extra[0];
+		extra += extra[0];
+	}
+	return NULL;
+}
+
+static struct usb_midi_out_jack_descriptor *find_usb_out_jack_descriptor(
+					struct usb_host_interface *hostif, uint8_t jack_id)
+{
+	unsigned char *extra = hostif->extra;
+	int extralen = hostif->extralen;
+
+	while (extralen > 4) {
+		struct usb_midi_out_jack_descriptor *outjd =
+				(struct usb_midi_out_jack_descriptor *)extra;
+
+		if (outjd->bLength > 4 &&
+		    outjd->bDescriptorType == USB_DT_CS_INTERFACE &&
+		    outjd->bDescriptorSubtype == UAC_MIDI_OUT_JACK &&
+				outjd->bJackID == jack_id)
+			return outjd;
+		if (!extra[0])
+			break;
+		extralen -= extra[0];
+		extra += extra[0];
+	}
+	return NULL;
+}
+
 static void snd_usbmidi_init_substream(struct snd_usb_midi *umidi,
-				       int stream, int number,
+				       int stream, int number, int jack_id,
 				       struct snd_rawmidi_substream **rsubstream)
 {
 	struct port_info *port_info;
 	const char *name_format;
+	struct usb_interface *intf;
+	struct usb_host_interface *hostif;
+	struct usb_midi_in_jack_descriptor *injd;
+	struct usb_midi_out_jack_descriptor *outjd;
+	uint8_t jack_name_buf[32];
+	uint8_t *default_jack_name = "MIDI";
+	uint8_t *jack_name = default_jack_name;
+	uint8_t iJack;
+	size_t sz;
+	int res;
 
 	struct snd_rawmidi_substream *substream =
 		snd_usbmidi_find_substream(umidi, stream, number);
@@ -1755,11 +1811,36 @@ static void snd_usbmidi_init_substream(struct snd_usb_midi *umidi,
 		return;
 	}
 
-	/* TODO: read port name from jack descriptor */
+	intf = umidi->iface;
+	if (intf && jack_id >= 0) {
+		hostif = intf->cur_altsetting;
+		iJack = 0;
+		if (stream != SNDRV_RAWMIDI_STREAM_OUTPUT) {
+			/* in jacks connect to outs */
+			outjd = find_usb_out_jack_descriptor(hostif, jack_id);
+			if (outjd) {
+				sz = USB_DT_MIDI_OUT_SIZE(outjd->bNrInputPins);
+				iJack = *(((uint8_t *) outjd) + sz - sizeof(uint8_t));
+			}
+		} else {
+			/* and out jacks connect to ins */
+			injd = find_usb_in_jack_descriptor(hostif, jack_id);
+			if (injd)
+				iJack = injd->iJack;
+		}
+		if (iJack != 0) {
+			res = usb_string(umidi->dev, iJack, jack_name_buf,
+			  ARRAY_SIZE(jack_name_buf));
+			if (res)
+				jack_name = jack_name_buf;
+		}
+	}
+
 	port_info = find_port_info(umidi, number);
-	name_format = port_info ? port_info->name : "%s MIDI %d";
+	name_format = port_info ? port_info->name :
+		(jack_name != default_jack_name  ? "%s %s" : "%s %s %d");
 	snprintf(substream->name, sizeof(substream->name),
-		 name_format, umidi->card->shortname, number + 1);
+		 name_format, umidi->card->shortname, jack_name, number + 1);
 
 	*rsubstream = substream;
 }
@@ -1794,6 +1875,7 @@ static int snd_usbmidi_create_endpoints(struct snd_usb_midi *umidi,
 				snd_usbmidi_init_substream(umidi,
 							   SNDRV_RAWMIDI_STREAM_OUTPUT,
 							   out_ports,
+							   endpoints[i].assoc_out_jacks[j],
 							   &umidi->endpoints[i].out->ports[j].substream);
 				++out_ports;
 			}
@@ -1801,6 +1883,7 @@ static int snd_usbmidi_create_endpoints(struct snd_usb_midi *umidi,
 				snd_usbmidi_init_substream(umidi,
 							   SNDRV_RAWMIDI_STREAM_INPUT,
 							   in_ports,
+							   endpoints[i].assoc_in_jacks[j],
 							   &umidi->endpoints[i].in->ports[j].substream);
 				++in_ports;
 			}
@@ -1846,7 +1929,7 @@ static int snd_usbmidi_get_ms_info(struct snd_usb_midi *umidi,
 	struct usb_host_endpoint *hostep;
 	struct usb_endpoint_descriptor *ep;
 	struct usb_ms_endpoint_descriptor *ms_ep;
-	int i, epidx;
+	int i, j, epidx;
 
 	intf = umidi->iface;
 	if (!intf)
@@ -1895,6 +1978,10 @@ static int snd_usbmidi_get_ms_info(struct snd_usb_midi *umidi,
 				endpoints[epidx].out_interval = 1;
 			endpoints[epidx].out_cables =
 				(1 << ms_ep->bNumEmbMIDIJack) - 1;
+			for (j = 0; j < ms_ep->bNumEmbMIDIJack; ++j)
+				endpoints[epidx].assoc_out_jacks[j] = ms_ep->baAssocJackID[j];
+			for (; j < ARRAY_SIZE(endpoints[epidx].assoc_out_jacks); ++j)
+				endpoints[epidx].assoc_out_jacks[j] = -1;
 			dev_dbg(&umidi->dev->dev, "EP %02X: %d jack(s)\n",
 				ep->bEndpointAddress, ms_ep->bNumEmbMIDIJack);
 		} else {
@@ -1912,6 +1999,10 @@ static int snd_usbmidi_get_ms_info(struct snd_usb_midi *umidi,
 				endpoints[epidx].in_interval = 1;
 			endpoints[epidx].in_cables =
 				(1 << ms_ep->bNumEmbMIDIJack) - 1;
+			for (j = 0; j < ms_ep->bNumEmbMIDIJack; ++j)
+				endpoints[epidx].assoc_in_jacks[j] = ms_ep->baAssocJackID[j];
+			for (; j < ARRAY_SIZE(endpoints[epidx].assoc_in_jacks); ++j)
+				endpoints[epidx].assoc_in_jacks[j] = -1;
 			dev_dbg(&umidi->dev->dev, "EP %02X: %d jack(s)\n",
 				ep->bEndpointAddress, ms_ep->bNumEmbMIDIJack);
 		}
@@ -2228,11 +2319,13 @@ static int snd_usbmidi_create_endpoints_midiman(struct snd_usb_midi *umidi,
 			snd_usbmidi_init_substream(umidi,
 						   SNDRV_RAWMIDI_STREAM_OUTPUT,
 						   cable,
+						   -1 /* prevent trying to find jack */,
 						   &umidi->endpoints[cable & 1].out->ports[cable].substream);
 		if (endpoint->in_cables & (1 << cable))
 			snd_usbmidi_init_substream(umidi,
 						   SNDRV_RAWMIDI_STREAM_INPUT,
 						   cable,
+						   -1 /* prevent trying to find jack */,
 						   &umidi->endpoints[0].in->ports[cable].substream);
 	}
 	return 0;

sound/usb/midi.h

@@ -13,6 +13,8 @@ struct snd_usb_midi_endpoint_info {
 	uint8_t  in_interval;
 	uint16_t out_cables;	/* bitmask */
 	uint16_t in_cables;	/* bitmask */
+	int16_t  assoc_in_jacks[16];
+	int16_t  assoc_out_jacks[16];
 };
 
 /* for QUIRK_MIDI_YAMAHA, data is NULL */