On Tue, Jun 24, 2014 at 05:51:16PM +0300, Mathias Nyman wrote: > On 06/24/2014 05:10 PM, Greg KH wrote: > > On Tue, Jun 24, 2014 at 05:14:42PM +0300, Mathias Nyman wrote: > >> From: Julius Werner <jwerner@xxxxxxxxxxxx> > >> > >> The current XHCI driver recalculates the Context Entries field in the > >> Slot Context on every add_endpoint() and drop_endpoint() call. In the > >> case of drop_endpoint(), it seems to assume that the add_flags will > >> always contain every endpoint for the new configuration, which is not > >> necessarily correct if you don't make assumptions about how the USB core > >> uses the add_endpoint/drop_endpoint interface (add_flags only contains > >> endpoints that are new additions in the new configuration). > >> > >> Furthermore, EP0_FLAG is not consistently set in add_flags throughout > >> the lifetime of a device. This means that when all endpoints are > >> dropped, the Context Entries field can be set to 0 (which is invalid and > >> may cause a Parameter Error) or -1 (which is interpreted as 31 and > >> causes the driver to keep using the old, incorrect value). > >> > >> The only surefire way to set this field right is to also take all > >> existing endpoints into account, and to force the value to 1 (meaning > >> only EP0 is active) if no other endpoint is found. This patch implements > >> that as a single step in the final check_bandwidth() call and removes > >> the intermediary calculations from add_endpoint() and drop_endpoint(). > >> > >> Signed-off-by: Julius Werner <jwerner@xxxxxxxxxxxx> > >> Signed-off-by: Mathias Nyman <mathias.nyman@xxxxxxxxxxxxxxx> > >> --- > >> drivers/usb/host/xhci.c | 51 +++++++++++++++++-------------------------------- > >> 1 file changed, 18 insertions(+), 33 deletions(-) > > > > Is this something for older (i.e. stable) kernels? > > > > This was intentionally left out of stable, reasoning in a previous mail was: > > "We discussed with Sarah that we should try this out and queue it for > usb-linus. This clearly fixes the generation of a invalid slot context > if all endpoints are dropped. > > But because there hasn't been any reported issue about the other case > this changes (always setting context entries to last valid ep in target > configuration), and spec still has this tiny contradiction in this case, > we should keep this out of stable. At least for now, until it gets some > real world testing coverage." > > The mail: > http://marc.info/?l=linux-usb&m=139879120000807&w=2 > > Or if you prefer this patch could go to usb-next instead. If it doesn't fix a known issue, then it shouldn't go to 3.16-final at this point in time, as I can't justify it being added. So I'll queue it up for usb-next instead right now. thanks, greg k-h -- 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
