On Wed, 20 Sep 2017, Kim Jaejoong wrote: > To. usb & input guys. > > While dig this report, i was wondering about bNumDescriptors in HID > descriptor. > HID document from usb.org said, 'this number must be at least one (1) > as a Report descriptor will always be present.' > > There is no mention of the order of class descriptors. Suppose you > have a HID device with a report descriptor and a physical descriptor. > > If you have the following hid descriptor in this case, > HID descriptor > bLength: 12 > bDescriptor Type: HID > .. skip > bNumDescriptors: 2 > bDescriptorType: physical > bDescriptorLength: any > bDescriptorType: Report > bDescriptorLength: any > > If the order of the report descriptor is the second as above, > usbhid_parse () will fail because my patch is only check the first > bDescriptor Type. > But If the order of the report descriptor is always first, there is no > problem. How do you think this?
The descriptors can appear in any order. You should not assume that the report descriptor will always come first. Alan Stern
