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--- Comment #34 from John Dallaway <[email protected]> 2010-10-21 22:20:33 BST --- (In reply to comment #32) > (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. Agreed. Composite devices have one device descriptor, one configuration descriptor and multiple interface descriptors. With the current USB slave infrastructure it would be easy enough to implement a new composite device but not so easy to re-use multiple existing function device packages to form a composite device. I think this should not affect the proposal for dynamic endpoint configuration. -- 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.
