USB: Fix up full-speed bInterval values in high-speed interrupt descriptor
Many device manufacturers are using full-speed bInterval values in high-speed
interrupt endpoint descriptors. If the bInterval value is greater than 16,
assume the device uses full-speed descriptors and fix the value accordingly.
Signed-off-by: Laurent Pinchart <laurent.pinchart@skynet.be>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
diff --git a/drivers/usb/core/config.c b/drivers/usb/core/config.c
index 9152e12..5e113db 100644
--- a/drivers/usb/core/config.c
+++ b/drivers/usb/core/config.c
@@ -85,15 +85,21 @@
memcpy(&endpoint->desc, d, n);
INIT_LIST_HEAD(&endpoint->urb_list);
- /* If the bInterval value is outside the legal range,
- * set it to a default value: 32 ms */
+ /* Fix up bInterval values outside the legal range. Use 32 ms if no
+ * proper value can be guessed. */
i = 0; /* i = min, j = max, n = default */
j = 255;
if (usb_endpoint_xfer_int(d)) {
i = 1;
switch (to_usb_device(ddev)->speed) {
case USB_SPEED_HIGH:
- n = 9; /* 32 ms = 2^(9-1) uframes */
+ /* Many device manufacturers are using full-speed
+ * bInterval values in high-speed interrupt endpoint
+ * descriptors. Try to fix those and fall back to a
+ * 32 ms default value otherwise. */
+ n = fls(d->bInterval*8);
+ if (n == 0)
+ n = 9; /* 32 ms = 2^(9-1) uframes */
j = 16;
break;
default: /* USB_SPEED_FULL or _LOW */
