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USB: unconfigure devices which have config 0

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Some USB devices do have a configuration 0, in contravention of the
USB spec.  Normally 0 is supposed to indicate that a device is
unconfigured.

While we can't change what the device is doing, we can change usbcore.
This patch (as852) allows usb_set_configuration() to accept a config
value of -1 as indicating that the device should be unconfigured.  The
request actually sent to the device will still contain 0 as the value.
But even if the device does have a configuration 0, dev->actconfig
will be set to NULL and dev->state will be set to USB_STATE_ADDRESS.

Without some sort of special-case handling like this, there is no way
to unconfigure these non-compliant devices.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Alan Stern
2007-02-08 16:40:43 -05:00
committed by Greg Kroah-Hartman
parent d1bbb60007
commit 3f141e2aed
4 changed files with 22 additions and 8 deletions
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2
drivers/usb/core/sysfs.c
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@ -63,7 +63,7 @@ set_bConfigurationValue(struct device *dev, struct device_attribute *attr,
struct usb_device *udev = to_usb_device(dev);
int config, value;
if (sscanf(buf, "%u", &config) != 1 || config > 255)
if (sscanf(buf, "%d", &config) != 1 || config < -1 || config > 255)
return -EINVAL;
usb_lock_device(udev);
value = usb_set_configuration(udev, config);