[ALSA] usb audio: Fix another Dallas quirk

Dallas USB speakers are buggy in more than one way. One of configs
they offer does not work at all.

Signed-off-by: Pavel Machek <pavel@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

diff --git a/sound/usb/usbaudio.c b/sound/usb/usbaudio.c
index 5c40c03..ff2e09a 100644 (file)
--- a/sound/usb/usbaudio.c
+++ b/sound/usb/usbaudio.c
@@ -2676,12 +2676,23 @@ static int parse_audio_endpoints(struct snd_usb_audio *chip, int iface_no)
        int format;
        struct audioformat *fp;
        unsigned char *fmt, *csep;
+       int num;
 
        dev = chip->dev;
 
        /* parse the interface's altsettings */
        iface = usb_ifnum_to_if(dev, iface_no);
-       for (i = 0; i < iface->num_altsetting; i++) {
+
+       num = iface->num_altsetting;
+
+       /*
+        * Dallas DS4201 workaround: It presents 5 altsettings, but the last
+        * one misses syncpipe, and does not produce any sound.
+        */
+       if (chip->usb_id == USB_ID(0x04fa, 0x4201))
+               num = 4;
+
+       for (i = 0; i < num; i++) {
                alts = &iface->altsetting[i];
                altsd = get_iface_desc(alts);
                /* skip invalid one */