[PATCH] 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 <[email protected]>

diff --git a/drivers/usb/core/config.c b/drivers/usb/core/config.c
index 35e27ff..ecf5838 100644
--- a/drivers/usb/core/config.c
+++ b/drivers/usb/core/config.c
@@ -85,15 +85,21 @@ static int usb_parse_endpoint(struct device *ddev, int cfgno, int inum,
 	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 */
-- 
1.5.1.6

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