usb: gadget: OS Feature Descriptors support
There is a custom (non-USB IF) extension to the USB standard: http://msdn.microsoft.com/library/windows/hardware/gg463182 They grant permission to use the specification - there is "Microsoft OS Descriptor Specification License Agreement" under the link mentioned above, and its Section 2 "Grant of License", letter (b) reads: "Patent license. Microsoft hereby grants to You a nonexclusive, royalty-free, nontransferable, worldwide license under Microsoft’s patents embodied solely within the Specification and that are owned or licensable by Microsoft to make, use, import, offer to sell, sell and distribute directly or indirectly to Your Licensees Your Implementation. You may sublicense this patent license to Your Licensees under the same terms and conditions." The said extension is maintained by Microsoft for Microsoft. Yet it is fairly common for various devices to use it, and a popular proprietary operating system expects devices to provide "OS descriptors", so Linux-based USB gadgets whishing to be able to talk to a variety of operating systems should be able to provide the "OS descriptors". This patch adds optional support for gadgets whishing to expose the so called "OS Feature Descriptors", that is "Extended Compatibility ID" and "Extended Properties". Hosts which do request "OS descriptors" from gadgets do so during the enumeration phase and before the configuration is set with SET_CONFIGURATION. What is more, those hosts never ask for configurations at indices other than 0. Therefore, gadgets whishing to provide "OS descriptors" must designate one configuration to be used with this kind of hosts - this is what os_desc_config is added for in struct usb_composite_dev. There is an additional advantage to it: if a gadget provides "OS descriptors" and designates one configuration to be used with such non-USB-compliant hosts it can invoke "usb_add_config" in any order because the designated configuration will be reported to be at index 0 anyway. This patch also adds handling vendor-specific requests addressed at device or interface and related to handling "OS descriptors". Signed-off-by:Andrzej Pietrasiewicz <andrzej.p@samsung.com> Acked-by: