[PATCH 2/2] 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.

[George Harker <george@george-graphics.co.uk>]

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>
---
 sound/usb/midi.c | 103 ++++++++++++++++++++++++++++++++++++++++++++---
 sound/usb/midi.h |   2 +
 2 files changed, 100 insertions(+), 5 deletions(-)

diff --git a/sound/usb/midi.c b/sound/usb/midi.c
index 610cf54ee..9efda4b06 100644
--- a/sound/usb/midi.c
+++ b/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;
diff --git a/sound/usb/midi.h b/sound/usb/midi.h
index 8c38aec22..3f153195c 100644
--- a/sound/usb/midi.h
+++ b/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 */
-- 
2.20.1