USB: skip Set-Interface(0) if already in altsetting 0
authorAlan Stern <stern@rowland.harvard.edu>
Mon, 1 Dec 2008 15:24:41 +0000 (10:24 -0500)
committerGreg Kroah-Hartman <gregkh@suse.de>
Wed, 17 Dec 2008 18:49:14 +0000 (10:49 -0800)
When a driver unbinds from an interface, usbcore always sends a
Set-Interface request to reinstall altsetting 0.  Unforunately, quite
a few devices have buggy firmware that crashes when it receives this
request.

To avoid such problems, this patch (as1180) arranges to send the
Set-Interface request only when the interface is not already in
altsetting 0.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
drivers/usb/core/driver.c

index 3d7793d93031525400d3ed746a60639ebed1d52f..8c081308b0e2d8bf2349d6b9e9703de0548213ac 100644 (file)
@@ -279,7 +279,9 @@ static int usb_unbind_interface(struct device *dev)
         * altsetting means creating new endpoint device entries).
         * When either of these happens, defer the Set-Interface.
         */
-       if (!error && intf->dev.power.status == DPM_ON)
+       if (intf->cur_altsetting->desc.bAlternateSetting == 0)
+               ;       /* Already in altsetting 0 so skip Set-Interface */
+       else if (!error && intf->dev.power.status == DPM_ON)
                usb_set_interface(udev, intf->altsetting[0].
                                desc.bInterfaceNumber, 0);
        else