Alan Stern wrote: > On Tue, 19 Dec 2006, Clemens Ladisch wrote: > > Alan Stern wrote: > > > Different interfaces in the same configuration are not allowed to use > > > the same endpoint. > > > > Which doesn't prevent M-Audio from building such devices. > > > > In this case, the driver has to take care to avoid using these > > interfaces at the same time. > > I don't understand this. A USB driver doesn't "use" interfaces; all it > does is send packets to various endpoints.
These are audio devices with isochrounous endpoints; the driver "uses" the interfaces by selecting a non-zero altsetting. (In theory, each audio interface is an independent audio device.) > So for example, if interface 0 and interface 1 both contain endpoint 2-in, > and your driver submits a request to transfer 64 bytes from that endpoint, > which interface are you "using"? The sample format is determined by the "used" altsetting. (In the case of the Quattro or OmniStudio, the device would sometimes return data formatted according to the last selected sample format, or sometimes 'combine' both sample formats and return garbage.) I'm not implying that any of this makes sense, or that anybody should design such a device. :-) Regards, Clemens ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys - and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV _______________________________________________ linux-usb-devel@lists.sourceforge.net To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
