On Tuesday 21 March 2006 9:31 am, Alan Stern wrote: > That's right. usb_ep_alloc_buffer doesn't really use the endpoint > argument, so it doesn't matter whether we specify the bulk-in or the > bulk-out endpoint. Basically, any buffer can be used with any endpoint > (except possibly endpoint 0).
That's not true. Controller drivers are certainly allowed to use that argument ... it's provided so that they _can_ use it. Some do. Example, if the endpoint isn't DMA-capable that call never needs to be implemented using dma_alloc_coherent() -- or perhaps a chip-specific call to allocate from dedicated RAM -- and can thus return normal cacheable buffers. But if it uses DMA, that's not true. Now "net2280.c" for example only has four DMA-capable endpoints, (ep-a, ep-b, ep-c, ep-d), and buffers allocated for one of those can be used with any of the other three. (Iff you're willing to have nonportable code in your gadget driver...) It also has three PIO-only endpoints (ep0, ep-e, ep-f) ... and buffers that are i/o coherent with respect those will NOT be DMA-coherent on all platforms. - Dave ------------------------------------------------------- This SF.Net email is sponsored by xPML, a groundbreaking scripting language that extends applications into web and mobile media. Attend the live webcast and join the prime developer group breaking into this new coding territory! http://sel.as-us.falkag.net/sel?cmd=lnk&kid=110944&bid=241720&dat=121642 _______________________________________________ linux-usb-devel@lists.sourceforge.net To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
