USB: unconfigure devices which have config 0
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>
diff --git a/drivers/usb/core/message.c b/drivers/usb/core/message.c
index 8aca357..74edaea 100644
--- a/drivers/usb/core/message.c
+++ b/drivers/usb/core/message.c
@@ -1316,6 +1316,14 @@
* use this kind of configurability; many devices only have one
* configuration.
*
+ * @configuration is the value of the configuration to be installed.
+ * According to the USB spec (e.g. section 9.1.1.5), configuration values
+ * must be non-zero; a value of zero indicates that the device in
+ * unconfigured. However some devices erroneously use 0 as one of their
+ * configuration values. To help manage such devices, this routine will
+ * accept @configuration = -1 as indicating the device should be put in
+ * an unconfigured state.
+ *
* USB device configurations may affect Linux interoperability,
* power consumption and the functionality available. For example,
* the default configuration is limited to using 100mA of bus power,
@@ -1347,10 +1355,15 @@
struct usb_interface **new_interfaces = NULL;
int n, nintf;
- for (i = 0; i < dev->descriptor.bNumConfigurations; i++) {
- if (dev->config[i].desc.bConfigurationValue == configuration) {
- cp = &dev->config[i];
- break;
+ if (configuration == -1)
+ configuration = 0;
+ else {
+ for (i = 0; i < dev->descriptor.bNumConfigurations; i++) {
+ if (dev->config[i].desc.bConfigurationValue ==
+ configuration) {
+ cp = &dev->config[i];
+ break;
+ }
}
}
if ((!cp && configuration != 0))
@@ -1359,6 +1372,7 @@
/* The USB spec says configuration 0 means unconfigured.
* But if a device includes a configuration numbered 0,
* we will accept it as a correctly configured state.
+ * Use -1 if you really want to unconfigure the device.
*/
if (cp && configuration == 0)
dev_warn(&dev->dev, "config 0 descriptor??\n");