From 436f5762bcd4929825a0725d4bc78337e6fc0d8f Mon Sep 17 00:00:00 2001 From: Alan Stern Date: Tue, 2 May 2006 15:22:41 -0400 Subject: [PATCH] [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 Signed-off-by: Greg Kroah-Hartman --- drivers/usb/core/hub.c | 23 +++++++++++++---------- 1 file changed, 13 insertions(+), 10 deletions(-) diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c index 0c87f73f293..90b8d43c6b3 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 */ -- 2.20.1