diff options
Diffstat (limited to 'drivers/usb/core/message.c')
| -rw-r--r-- | drivers/usb/core/message.c | 22 |
1 files changed, 18 insertions, 4 deletions
diff --git a/drivers/usb/core/message.c b/drivers/usb/core/message.c index 8aca3574c2b..74edaea5665 100644 --- a/drivers/usb/core/message.c +++ b/drivers/usb/core/message.c @@ -1316,6 +1316,14 @@ static void release_interface(struct device *dev) * 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 @@ int usb_set_configuration(struct usb_device *dev, int configuration) 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 @@ int usb_set_configuration(struct usb_device *dev, int configuration) /* 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"); |