usb-core bInterval quirk

This patch adds a usb quirk to support devices with interupt endpoints
and bInterval values expressed as microframes. The quirk causes the
parse endpoint function to modify the reported bInterval to a standards
conforming value.

There is currently code in the endpoint parser that checks for
bIntervals that are outside of the valid range (1-16 for USB 2+ high
speed and super speed interupt endpoints). In this case, the code assumes
the bInterval is being reported in 1ms frames. As well, the correction
is only applied if the original bInterval value is out of the 1-16 range.

With this quirk applied to the device, the bInterval will be
accurately adjusted from microframes to an exponent.

Signed-off-by: James P Michels III <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/usb/core/config.c

···
 			if (n == 0)
 				n = 9;	/* 32 ms = 2^(9-1) uframes */
 			j = 16;
+
+			/*
+			 * Adjust bInterval for quirked devices.
+			 * This quirk fixes bIntervals reported in
+			 * linear microframes.
+			 */
+			if (to_usb_device(ddev)->quirks &
+				USB_QUIRK_LINEAR_UFRAME_INTR_BINTERVAL) {
+				n = clamp(fls(d->bInterval), i, j);
+				i = j = n;
+			}
 			break;
 		default:		/* USB_SPEED_FULL or _LOW */
 			/* For low-speed, 10 ms is the official minimum.

drivers/usb/core/quirks.c

···
 	/* SKYMEDI USB_DRIVE */
 	{ USB_DEVICE(0x1516, 0x8628), .driver_info = USB_QUIRK_RESET_RESUME },
 
+	/* Razer - Razer Blade Keyboard */
+	{ USB_DEVICE(0x1532, 0x0116), .driver_info =
+			USB_QUIRK_LINEAR_UFRAME_INTR_BINTERVAL },
+
 	/* BUILDWIN Photo Frame */
 	{ USB_DEVICE(0x1908, 0x1315), .driver_info =
 			USB_QUIRK_HONOR_BNUMINTERFACES },

include/linux/usb/quirks.h

···
    descriptor */
 #define USB_QUIRK_DELAY_INIT		0x00000040
 
+/*
+ * For high speed and super speed interupt endpoints, the USB 2.0 and
+ * USB 3.0 spec require the interval in microframes
+ * (1 microframe = 125 microseconds) to be calculated as
+ * interval = 2 ^ (bInterval-1).
+ *
+ * Devices with this quirk report their bInterval as the result of this
+ * calculation instead of the exponent variable used in the calculation.
+ */
+#define USB_QUIRK_LINEAR_UFRAME_INTR_BINTERVAL	0x00000080
+
 #endif /* __LINUX_USB_QUIRKS_H */