> Hmm. Wouldn't it be safer to have a quirk for this, and only enable > the workaround if the Asmedia controller is detected? This code is so > complicated that it is difficult to see whether this could have a > harmful effect on controllers without the bug.
Sorry for making it complicated, but it kinda has been like that before already... I don't think the new patch adds much confusion on its own. I would really advise against making this a quirk: checking for it in every case essentially doesn't cost us anything (just one more register compare that is negligible against all the cache-coherent memory accesses of walking the ring), and hardcoding a quirk would mean that we have to identify and add every host controller that does this individually. I still haven't seen anything in the XHCI spec that actually forbids this behavior, so it might be a perfectly legal interpretation and who knows how many host controllers chose to do it that way. Until we find them all, we would have some really bad and hard to track down bugs on those controllers (we really just got lucky this time that Maciej was able to catch it in a bisect). I think it's better to program the driver defensively and able to deal with unexpected situations in general. -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
