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--- Comment #32 from Chris Holgate <[email protected]> 2010-10-21 19:32:15 BST --- (In reply to comment #31) > While I haven't looked through the spec for a while, I believe that you _can_ > have multiple class drivers on a single device without using a virtual hub. I > think it's called a composite device. The descriptor arrangement is a bit > more > complicated, but it's still possible. Your recollection of the spec is obviously better than mine. As you say, composite devices are supported and I should probably have used the Google before posting misleading rubbish! However, a single device can still only have one control endpoint and one root descriptor, which means the scenario John mentioned of multiple class drivers calling usbs_start with different (or even the same) control endpoint data structures should never happen. I think that supporting composite drivers is really an issue for a notional USB class driver framework. As far as the existing low level USB slave drivers are concerned, a USB device is just a bundle of endpoints and a bunch of arbitrary descriptors. IMHO that is exactly the right level of abstraction - and any additional support for composite drivers should be added as an extra layer of abstraction between the low level USB slave driver and the class function drivers. -- Configure bugmail: http://bugs.ecos.sourceware.org/userprefs.cgi?tab=email ------- You are receiving this mail because: ------- You are on the CC list for the bug.
