On Mon, Nov 26, 2012 at 11:22:06AM -0800, Greg KH wrote: > On Mon, Nov 26, 2012 at 12:45:34PM +0000, Andy Green wrote: > > This adds a small optional API into drivers/base which deals with generating, > > matching and registration of wildcard device paths. > > > > >From a struct device * you can generate a string like > > > > /platform/usbhs_omap/ehci-omap.0/usb1/1-1 > > > > which enapsulates the path of the device's connection to the board. > > > > These can be used to match up other assets, for example struct regulators, > > that have been registed elsewhere with a device instance that is probed > > asynchronously from the other board assets. > > > > If your device is on a bus, as it probably is, the device path will feature > > redundant bus indexes that do not contain information about the connectivity. > > Huh? A bus "index" does show the connectivity, well, one type of > connectivity, but perhaps it's not the one _you_ happen to want at the > moment. Which is fine, but I don't see why you want to try to figure > this out using the device path in the first place, surely you have some > other way that the hardware can describe itself to the kernel as to > where it needs to be hooked up to? > > > For example if more than one driver can generate devices on the same bus, > > then the ordering of device probing will change the path, despite the > > connectivity remains the same. > > That's an expected thing, I don't see the issue here. > > > For that reason, to get a deterministic path for matching, wildcards are > > allowed. If your target device has the path > > Wait, no, why would you want a deterministic path and have that > hard-coded into the kernel here? You can't rely on that any more than > userspace can, so let's not start making the mistake that lots of > userspace programmers originally did when they started using sysfs > please. We have learned from our past mistakes. > > > /platform/usbhs_omap/ehci-omap.0/usb1/1-1 Oh, and further proof of this, there are patches floating around to drop the "platform" name from the sys/drivers/ tree, so your driver just broke if that goes through, showing you really don't want to be hard-coding sysfs paths in any type of logic. 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
