On Wed, 6 Jun 2012, Sarah Sharp wrote: > There are two ways to deal with sglists: > > 1. Set urb->sg and everything else in the URB, and call > usb_submit_urb(). This is what the UAS driver does, and the URB call > back will be asychronous. > > 2. Call usb_sg_init() with a sglist. This will set up urb->sg. Then > call usb_sg_wait() to wait on all the URBs to be completed. This is > the path the usb-storage driver uses, and this path is synchronous. > > The only reason the usb-storage driver uses usb_sg_wait() is because it > is designed to submit each part of the SCSI command and wait on each of > the two to three URBs that make up that command. No. The reason usb-storage uses usb_sg_wait() is because it has to work with _all_ host controller drivers, not just those that support SG. The same should be true of usbfs. 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
