On Mon, 16 May 2011, Clemens Ladisch wrote: > Xiaofan Chen wrote: > > We just have a discussion on libusb-win32 about a device > > from Microsoft. Xbox Kinnect has the Xbox NUI Audio device which > > is a high speed USB device and it has an isoc endpoint with > > bInterval of 5. [...] > > The question is whether this device violates USB specification? > > This bInterval value does not violate the spec. > > What does violate the spec is that there is no alternate setting with > an iso bandwidth of zero. (Having iso and bulk endpoints in the same > interface is just bad design. And it's probably too much to ask for > a class-compliant device, as that would make the device portable.) > > > Apparently it is supported under Linux. Does Linux has > > similar limitation about the bInterval value for high > > speed isoc endpoint like Windows? > > No, Linux supports all intervals that the spec says it must support. Actually there are upper limits on the supported interval values. It depends on the host controller hardware; typical limits on periodic interval values are 1 second or 0.25 second. For a high-speed device, this corresponds to bInterval = 13 or 11. I'm not aware of any devices requiring intervals longer than that. Alan Stern -- 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
