[PATCH] USB: usbcore: don't check the device's power source

The choose_configuration() routine contains code the determine the
device's power source, so that configurations requiring external power
can be ruled out if the device is running on bus power.  Unfortunately
it turns out that some devices have errors in their config descriptors
and other devices don't like the GET_DEVICE_STATUS request.

Since that information wasn't used for anything else, this patch (as673)
removes the code, leaving only a comment.  It fixes bugzilla entry
#6448.

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

1 files changed, 13 insertions, 10 deletions

diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index 0c87f73f2933..90b8d43c6b33 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -1168,19 +1168,9 @@ static inline const char *plural(int n)
 static int choose_configuration(struct usb_device *udev)
 {
 	int i;
-	u16 devstatus;
-	int bus_powered;
 	int num_configs;
 	struct usb_host_config *c, *best;
 
-	/* If this fails, assume the device is bus-powered */
-	devstatus = 0;
-	usb_get_status(udev, USB_RECIP_DEVICE, 0, &devstatus);
-	le16_to_cpus(&devstatus);
-	bus_powered = ((devstatus & (1 << USB_DEVICE_SELF_POWERED)) == 0);
-	dev_dbg(&udev->dev, "device is %s-powered\n",
-			bus_powered ? "bus" : "self");
-
 	best = NULL;
 	c = udev->config;
 	num_configs = udev->descriptor.bNumConfigurations;
@@ -1197,6 +1187,19 @@ static int choose_configuration(struct usb_device *udev)
 		 * similar errors in their descriptors.  If the next test
 		 * were allowed to execute, such configurations would always
 		 * be rejected and the devices would not work as expected.
+		 * In the meantime, we run the risk of selecting a config
+		 * that requires external power at a time when that power
+		 * isn't available.  It seems to be the lesser of two evils.
+		 *
+		 * Bugzilla #6448 reports a device that appears to crash
+		 * when it receives a GET_DEVICE_STATUS request!  We don't
+		 * have any other way to tell whether a device is self-powered,
+		 * but since we don't use that information anywhere but here,
+		 * the call has been removed.
+		 *
+		 * Maybe the GET_DEVICE_STATUS call and the test below can
+		 * be reinstated when device firmwares become more reliable.
+		 * Don't hold your breath.
 		 */
 #if 0
 		/* Rule out self-powered configs for a bus-powered device */