On Wed, Jun 6, 2012 at 10:26 AM, Xiaofan Chen <xiaofanc@xxxxxxxxx> wrote: > On Wed, Jun 6, 2012 at 3:32 AM, Sarah Sharp > <sarah.a.sharp@xxxxxxxxxxxxxxx> wrote: >> On Tue, Jun 05, 2012 at 01:12:44PM -0400, Alan Stern wrote: >>> On Tue, 5 Jun 2012, Sarah Sharp wrote: >>> >>> > Or just change libusb to not break up large transfers, and get rid of >>> > the BULK_CONTINUATION flag all together. libusb should submit >>> > the whole transfer to usbfs with an iovec. usbfs can then: >>> > >>> > a) verify each iovec entry is not too long >>> > b) verify the total length of the iovec isn't too big >>> > c) translate each iovec entry into one sglist vector >>> > d) submit one URB with a populated sglist to the USB core >>> >>> I think this would work. But it wouldn't help people trying to use >>> libusb with xHCI on older kernels. >> >> No, it wouldn't help them. At some point though, users just need to >> upgrade their kernels. And if enterprise distro kernels decide they >> care about those particular users, they can pick up the patches. I >> think Hans was already volunteering to try and push the necessary kernel >> changes for RHEL. > > I think this is fair. xHCI on older kernels may not work well > anyway. BTW, It is similar under Windows that xHCI may or > may not work well on Windows XP/Vista/7 where there is no > official Microsoft driver for them. > > On the other hand, libusb/libusbx should probably need > to put a note that it may not work with USB 3.0 ports prior to kernel > 3.x (where 3.x is the first kernel to solve this issue). Or if there will no kernel changes due to the complexity required, then we need to put a note that prior to libusb-1.0.10 / libusbx-1.0.13 (if that is the first version to follow Sarah's change), libusb/libusbx may not work with USB 3.0 ports. >> It might be worth it to ensure that the old usbfs calls without iovecs >> can co-exist with the new calls, so that we don't break older API. That >> will make it easier to convince distro kernels to pick up the usbfs >> changes. -- Xiaofan -- 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
