On Fri, Mar 11, 2011 at 04:48:50PM +0000, Mark Brown wrote: > On Fri, Mar 11, 2011 at 08:35:22AM -0800, Greg KH wrote: > > On Fri, Mar 11, 2011 at 04:27:59PM +0000, Mark Brown wrote: > > > > I'm actually not that fussed about the MAC address use case itself and > > > do tend to agree with you that that's handlable in userspace but for the > > > other things that might need to be configured there's a lot of things > > > that for non-discoverable buses we're currently passing through platform > > > data so switching to bouncing things through userspace would itself be a > > > substantial change from other systems. > > > But USB _is_ discoverable, that's my point. > > USB itself is discoverable but the when the USB bus you're looking at is > one that's soldered down onto a board in a specific design all bets are > off regarding how complete the information you get will be. On a basic > level the designers may have done things like omit the configuration > EEPROMs that would set the device IDs that the driver should be relying > on to identify the hardware configuration. There may be other, nastier, > things going on. Then you use the existing platform data for your USB host controller driver. Doesn't that work today just fine? > > > You can't in general rely on the system being neatly abstracted and > > > while discoverable buses do avoid many problems in this sort of area > > > there are still things which can only be discovered through reference to > > > the schematics or similar, especially if you care about the microamps. > > > Again, that's not USB, so it isn't relevant here. > > You really can't make this assumption about discoverable buses on > embedded devices. The discoverability will get you most of the way > there but not always all of the way there. Then the bus is not really USB, sorry. USB is discoverable, _and_ can support enumeration in non-deterministic ways. If people are using it in other ways then it is not USB and is something else. 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
