Messages in this thread | | | Date | Wed, 6 Jan 2016 16:36:01 +0100 | From | "Steinar H. Gunderson" <> | Subject | Re: [PATCH] Add support for usbfs zerocopy. |
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On Wed, Jan 06, 2016 at 04:22:12PM +0100, Peter Stuge wrote: >>> Our interface for zero copy reads/writes is O_DIRECT, and that requires >>> not special memory allocation, just proper alignment. >> But that assumes you are using I/O using read()/write(). There's no way you >> can shoehorn USB isochronous reads into the read() interface, O_DIRECT or not. > How about aio?
I don't really see how; a USB device does not look much like a file. (Where would you stick the endpoint, for one? And how would you ever submit an URB with multiple packets in it, which is essential?) It feels a bit like trying to use UDP sockets with only read() and write().
In any case, the usbfs interface already exists and is stable. This is about extending it; replacing it with something new from scratch to get zerocopy would seem overkill.
/* Steinar */ -- Software Engineer, Google Switzerland
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