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-rw-r--r--sound/usb/quirks.c19
1 files changed, 16 insertions, 3 deletions
diff --git a/sound/usb/quirks.c b/sound/usb/quirks.c
index acc12f0..2c97185 100644
--- a/sound/usb/quirks.c
+++ b/sound/usb/quirks.c
@@ -387,11 +387,13 @@ static int snd_usb_fasttrackpro_boot_quirk(struct usb_device *dev)
* rules
*/
err = usb_driver_set_configuration(dev, 2);
- if (err < 0) {
+ if (err < 0)
snd_printdd("error usb_driver_set_configuration: %d\n",
err);
- return -ENODEV;
- }
+ /* Always return an error, so that we stop creating a device
+ that will just be destroyed and recreated with a new
+ configuration */
+ return -ENODEV;
} else
snd_printk(KERN_INFO "usb-audio: Fast Track Pro config OK\n");
@@ -859,6 +861,17 @@ void snd_usb_endpoint_start_quirk(struct snd_usb_endpoint *ep)
if ((le16_to_cpu(ep->chip->dev->descriptor.idVendor) == 0x23ba) &&
ep->type == SND_USB_ENDPOINT_TYPE_SYNC)
ep->skip_packets = 4;
+
+ /*
+ * M-Audio Fast Track C400 - when packets are not skipped, real world
+ * latency varies by approx. +/- 50 frames (at 96KHz) each time the
+ * stream is (re)started. When skipping packets 16 at endpoint start
+ * up, the real world latency is stable within +/- 1 frame (also
+ * across power cycles).
+ */
+ if (ep->chip->usb_id == USB_ID(0x0763, 0x2030) &&
+ ep->type == SND_USB_ENDPOINT_TYPE_DATA)
+ ep->skip_packets = 16;
}
void snd_usb_ctl_msg_quirk(struct usb_device *dev, unsigned int pipe,
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