On Wednesday 24 October 2012 12:38:42 Alan Stern wrote: > On Wed, 24 Oct 2012, Stephen Warren wrote: > > > On 10/24/2012 09:26 AM, Sebastian Andrzej Siewior wrote: > > > On Wed, Oct 24, 2012 at 10:57:00AM -0400, Alan Stern wrote: > > >> Under the circumstances, do we really need a new binding document for > > >> the ehci-platform driver? > > > > It seems reasonable to add the new properties to usb-ehci.txt, since > > they do describe the HW. > > > > >> We should be able to use the existing > > >> usb-ehci binding, perhaps with some new properties added: > > >> > > >> has-synopsys-hc-bug > > >> no-io-watchdog > > >> has-tt > > > > That sounds fine to me. > > > > However, there is an implementation issue here. I believe the way Linux > > searches for a driver for a particular node is: > > > > for every driver that's registered > > if the driver's supported compatible list matches the device > > use the driver > > > > (See drivers/base/platform.c:platform_match() which implements the if > > statement above, and I assume the driver core implements the outer for > > loop above) > > Yes, it does. > > > That means that if the generic driver supports compatible="usb-ehci", it > > may "steal" device nodes that have > > compatible="something-custom","usb-ehci", even if there's a driver > > specifically for "something-custom". We would need to re-arrange the > > driver matching code to: > > > > for each compatible value in the node: > > for each driver that's registered: > > if the driver supports the compatible value: > > use the driver. > > Which might be difficult since the inner loop would be controlled by > the outer code in the driver core. > > How do we determine which existing drivers claim to support usb-ehci? > A quick search under arch/ and drivers/ turns up nothing but > drivers/usb/host/ehci-ppc-of.c. Changing it to a more HW-specific > match should be easy enough, and then "usb-ehci" would be safe to use > in ehci-platform.c. As long as no one enables both ehci-platform and ehci-ppc-of at the same time there is no problem. ehci-ppc-of should be removed in favor of ehci-platform and make sure that the specific quirk in ehci-ppc-of also gets ported, other that I see no issue using "usb-ehci" as the least detailed compatible property name. -- Florian -- 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
