* Felipe Balbi | 2012-08-16 09:30:05 [+0300]: >I couldn't find anywhere in the USB Specification >where it requires us to make sure all interfaces start >on Alternate Setting zero. IMHO, we should consider >initial state as UNKNOWN and not rely on that being >zero or anything. Table 9-1 in USB2.0 spec says once a device is configured (after USB_REQ_SET_CONFIGURATION) is may use its functions. So the default function should be activated. 9.6.5 says: |An interface may include alternate settings that allow the endpoints |and/or their characteristics to be varied after the device has been |configured. The default setting for an interface is always alternate |setting zero. |The SetInterface() request is used to select an alternate setting or to |return to the default setting. That means we have to start at zero. The host may change it, it may not use SetInterface() at all if the default setting is fine. 9.1.1.5 says: |Configuring a device or changing an alternate setting causes all of the status |and configuration values associated with endpoints in the affected |interfaces to be set to their default values. I think we can skip ->set_alt() if the old setting is the same as the new one. Sebastian -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
