On Wed, 6 Jun 2012, Sarah Sharp wrote: > Should we add an asynchronous scatter-gather interface to the USB core > that falls back to submitting multiple URBs if the host controller > doesn't have a native scatter gather interface? Pete Zaitcev and I discussed changing usb_sg_wait and friends to be asynchronous some time ago. I even posted a patch or two to do it. In the end it didn't seem worth the trouble. (This was back before native SG support was added to any of the HCDs.) I don't see that UAS really needs this. Nobody should be using UAS with an HCD that doesn't support SG operation. But usbfs may be a good reason for doing it. Or it could be implemented entirely within usbfs instead of changing usb_sg_*. > What would it mean to have an asynchronous callback for potentially > multiple URBs? The USB core could submit each URB one at a time, with Probably not one at a time. Maybe all at once, the way usb_sg_wait works now, or maybe in bunches. > the Nth URB being submitted from a USB core completion callback. Then > the driver's completion function could be called when all the URBs > complete (or one URB fails with an error status, and the other URBs > aren't submitted). Rather: or one URB fails with an error status and all the others either get cancelled or don't get submitted. Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
