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 <james.p.michels@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 11 insertions, 0 deletions

diff --git a/drivers/usb/core/config.c b/drivers/usb/core/config.c
index 1ab4df1de2da..b2a540b43f97 100644
--- a/drivers/usb/core/config.c
+++ b/drivers/usb/core/config.c
@@ -199,6 +199,17 @@ static int usb_parse_endpoint(struct device *ddev, int cfgno, int inum,
 			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.