ALSA: usb-audio: workaround for iface reset issue

The recently introduced sample rate validation code seems causing a
problem on some devices; namely, after performing this, the bus gets
screwed and it influences even on other USB devices.
As a quick workaround, perform it only for the necessary devices;
currently MOTU devices are known to need the valid altset checks, so
filter out other devices.

Fixes: 93db51d06b32 ("ALSA: usb-audio: Check valid altsetting at parsing rates for UAC2/3")
Reported-by: Jamie Heilman <jamie@audible.transient.net>
BugLink: https://bugzilla.suse.com/show_bug.cgi?id=1178203
Link: https://lore.kernel.org/r/20210123155842.22652-1-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>

diff --git a/sound/usb/format.c b/sound/usb/format.c
index 9ebc5d202c87398fa4e622acd58295d6bc356df3..e6ff317a678520a20ff5f6109886d5018fab9043 100644 (file)
--- a/sound/usb/format.c
+++ b/sound/usb/format.c
@@ -466,6 +466,17 @@ static int validate_sample_rate_table_v2v3(struct snd_usb_audio *chip,
        unsigned int nr_rates;
        int i, err;
 
+       /* performing the rate verification may lead to unexpected USB bus
+        * behavior afterwards by some unknown reason.  Do this only for the
+        * known devices.
+        */
+       switch (USB_ID_VENDOR(chip->usb_id)) {
+       case 0x07fd: /* MOTU */
+               break;
+       default:
+               return 0; /* don't perform the validation as default */
+       }
+
        table = kcalloc(fp->nr_rates, sizeof(*table), GFP_KERNEL);
        if (!table)
                return -ENOMEM;