USB: Handle bogus low-speed Bulk endpoints

A noticeable number of low-speed devices mistakenly include
descriptors for Bulk endpoints, which is forbidden by the USB spec.
In an attempt to make such devices more usable, this patch (as924)
converts the descriptors to Interrupt with an interval of 1 ms.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 15 insertions, 0 deletions

diff --git a/drivers/usb/core/config.c b/drivers/usb/core/config.c
index dd3482328ad2..9152e12dcf71 100644
--- a/drivers/usb/core/config.c
+++ b/drivers/usb/core/config.c
@@ -124,6 +124,21 @@ static int usb_parse_endpoint(struct device *ddev, int cfgno, int inum,
                 endpoint->desc.bInterval = n;
         }
 
+        /* Some buggy low-speed devices have Bulk endpoints, which is
+         * explicitly forbidden by the USB spec.  In an attempt to make
+         * them usable, we will try treating them as Interrupt endpoints.
+         */
+        if (to_usb_device(ddev)->speed == USB_SPEED_LOW &&
+                        usb_endpoint_xfer_bulk(d)) {
+                dev_warn(ddev, "config %d interface %d altsetting %d "
+                    "endpoint 0x%X is Bulk; changing to Interrupt\n",
+                    cfgno, inum, asnum, d->bEndpointAddress);
+                endpoint->desc.bmAttributes = USB_ENDPOINT_XFER_INT;
+                endpoint->desc.bInterval = 1;
+                if (le16_to_cpu(endpoint->desc.wMaxPacketSize) > 8)
+                        endpoint->desc.wMaxPacketSize = cpu_to_le16(8);
+        }
+
         /* Skip over any Class Specific or Vendor Specific descriptors;
          * find the next endpoint or interface descriptor */
         endpoint->extra = buffer;