ALSA CVS update - Clemens Ladisch <clemens@ladisch.de>

USB generic driver
add comments in USB MIDI vendor-specific detection functions

diff --git a/sound/usb/usbmidi.c b/sound/usb/usbmidi.c
index 443365a360cecba3a49bfcfef134dd9b1384ee68..ec81e2733be13af1fb5f0dffd308fc4d667fcc1d 100644 (file)
--- a/sound/usb/usbmidi.c
+++ b/sound/usb/usbmidi.c
@@ -1015,6 +1015,10 @@ static int snd_usbmidi_detect_yamaha(snd_usb_midi_t* umidi,
        if (intfd->bNumEndpoints < 1)
                return -ENOENT;
 
+       /*
+        * For each port there is one MIDI_IN/OUT_JACK descriptor, not
+        * necessarily with any useful contents.  So simply count 'em.
+        */
        for (cs_desc = hostif->extra;
             cs_desc < hostif->extra + hostif->extralen && cs_desc[0] >= 2;
             cs_desc += cs_desc[0]) {
@@ -1049,6 +1053,16 @@ static int snd_usbmidi_create_endpoints_midiman(snd_usb_midi_t* umidi,
                return -ENOENT;
        hostif = intf->altsetting;
        intfd = get_iface_desc(hostif);
+       /*
+        * The various MidiSport devices have more or less random endpoint
+        * numbers, so we have to identify the endpoints by their index in
+        * the descriptor array, like the driver for that other OS does.
+        *
+        * There is one interrupt input endpoint for all input ports, one
+        * bulk output endpoint for even-numbered ports, and one for odd-
+        * numbered ports.  Both bulk output endpoints have corresponding
+        * input bulk endpoints (at indices 1 and 3) which aren't used.
+        */
        if (intfd->bNumEndpoints < (endpoint->out_cables > 0x0001 ? 5 : 3)) {
                snd_printdd(KERN_ERR "not enough endpoints\n");
                return -ENOENT;