On Tue, 23 Oct 2012, Stephen Warren wrote: > > Nothing intrinsically distinguishes this class of hardware. The only > > thing these devices have in common is that they can be managed by > > Linux's ehci-platform driver. > > I don't agree. They're all EHCI USB controllers (or all EHCI USB > controllers that don't require custom drivers due to quirks), which is a > much more general statement than anything related to which driver Linux > uses for them. That's true, but it doesn't distinguish these devices. There are other EHCI controllers with no quirks that nevertheless can't be handled by ehci-platform because they have requirements (_not_ quirks) that ehci-platform is unable to deal with currently -- clocks or power supplies or special register settings or PHYs or etc. > > In essense, we're trying to say that the HW is compatible with a > > particular driver rather than with some other type of HW. > > Using a compatible value in order to pick a specific driver in Linux is > explicitly against the device tree design principles; DT is supposed to > represent just the hardware. > > > Maybe DT > > wasn't intended to provide this kind of information, but it seems like > > a logical thing to do. Unless DT already offers some other way to > > accomplish the same thing? > > The typical way is for the Linux driver to declare that is supports a > variety of different HW models. > > Admittedly this is annoying when there are many HW models that otherwise > wouldn't need any driver changes, hence the desire to (additionally) > include some generic value in the compatible field, but again, what that > generic value is should be driven by the HW itself, not the SW that's > using it. Okay, fine. But then what should the binding documentation specify for the compatible value? A list of all the HW models that the driver currently supports? 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
