On Mon, 9 Jan 2012, Sebastian Andrzej Siewior wrote: > On 01/09/2012 03:23 PM, Matthew Wilcox wrote: > > On Mon, Jan 09, 2012 at 01:55:02PM +0100, Sebastian Andrzej Siewior wrote: > >> Hi Sarah, > >> > >> I've been looking into UAS support for hcds without support for sg. > > > > I think that's fundamentally the wrong approach. Instead, HCDs should > > be modified to add support for SGs. I posted a patch series that made > > progress towards that goal a while back. > > That is what Felipe and I decided for the gadget framework. > Alan / Greg, any comments from your side? There are lots of little host controller drivers, and verifying that SG support has been correctly added to each of them will be nearly impossible. On the other hand, most of those drivers don't matter much as far as UAS is concerned. When the most commonly used HCDs all support SG, that should be good enough. UAS can refuse to bind if the host controller doesn't work with SG. And similarly, in that situation usb-storage should accept a device that has both BOT and UAS altsettings. It would be nice to have a Kconfig variable (CONFIG_USB_HCD_HAS_SG or something like that) which would be selected by all the HC drivers supporting SG, and which UAS would depend on. That way it would be impossible to build the UAS driver on systems where none of the HCDs will work with it. 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
