[PATCH] USB: Fix up bogus bInterval values in endpoint descriptors

This patch adds code to check for endpoint descriptor bInterval values
outside the legal limits. Illegal values are fixed or set to 32 ms, which
seems like a reasonable default.

This fixes Bugzilla #8432.

Signed-off-by: Laurent Pinchart <[email protected]>

diff --git a/drivers/usb/core/config.c b/drivers/usb/core/config.c
index bfb3731..ecf5838 100644
--- a/drivers/usb/core/config.c
+++ b/drivers/usb/core/config.c
@@ -1,4 +1,5 @@
 #include <linux/usb.h>
+#include <linux/usb/ch9.h>
 #include <linux/module.h>
 #include <linux/init.h>
 #include <linux/slab.h>
@@ -49,7 +50,7 @@ static int usb_parse_endpoint(struct device *ddev, int 
cfgno, int inum,
 	unsigned char *buffer0 = buffer;
 	struct usb_endpoint_descriptor *d;
 	struct usb_host_endpoint *endpoint;
-	int n, i;
+	int n, i, j;
 
 	d = (struct usb_endpoint_descriptor *) buffer;
 	buffer += d->bLength;
@@ -84,6 +85,51 @@ static int usb_parse_endpoint(struct device *ddev, int 
cfgno, int inum,
 	memcpy(&endpoint->desc, d, n);
 	INIT_LIST_HEAD(&endpoint->urb_list);
 
+	/* 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:
+			/* 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 */
+			/* For low-speed, 10 ms is the official minimum.
+			 * But some "overclocked" devices might want faster
+			 * polling so we'll allow it. */
+			n = 32;
+			break;
+		}
+	} else if (usb_endpoint_xfer_isoc(d)) {
+		i = 1;
+		j = 16;
+		switch (to_usb_device(ddev)->speed) {
+		case USB_SPEED_HIGH:
+			n = 9;		/* 32 ms = 2^(9-1) uframes */
+			break;
+		default:		/* USB_SPEED_FULL */
+			n = 6;		/* 32 ms = 2^(6-1) frames */
+			break;
+		}
+	}
+	if (d->bInterval < i || d->bInterval > j) {
+		dev_warn(ddev, "config %d interface %d altsetting %d "
+		    "endpoint 0x%X has an invalid bInterval %d, "
+		    "changing to %d\n",
+		    cfgno, inum, asnum,
+		    d->bEndpointAddress, d->bInterval, n);
+		endpoint->desc.bInterval = n;
+	}
+
 	/* Skip over any Class Specific or Vendor Specific descriptors;
 	 * find the next endpoint or interface descriptor */
 	endpoint->extra = buffer;
-- 
1.5.1.6


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