Hi Stephen, On 29 April 2016 at 10:23, Stephen Warren <swar...@wwwdotorg.org> wrote: > On 04/29/2016 07:23 AM, Simon Glass wrote: >> >> Hi Stephen, >> >> On 28 April 2016 at 09:55, Stephen Warren <swar...@wwwdotorg.org> wrote: >>> >>> On 04/27/2016 10:50 PM, Simon Glass wrote: >>>> >>>> >>>> Hi Stephen, >>>> >>>> On 26 April 2016 at 15:30, Stephen Warren wrote: >>>> > It is possible for HW to contain multiple instances of the same >>>> device. >>>> In >>>> > this case, the name passed to device_bind() may not be unique across >>>> all >>>> > devices within its uclass. One example is a system with multiple >>>> identical >>>> > PCI Ethernet devices. Another might be a system with multiple >>>> identical >>>> > I2C GPIO expanders, each connected to a separate I2C bus, yet using >>>> the >>>> > same I2C address on that bus and hence having the same DT node name. >>>> > >>>> > Enhance the code to detect this situation, and append a sequence >>>> number so >>>> > the device name to ensure uniqueness. >>>> > >>>> > Signed-off-by: Stephen Warren <swar...@nvidia.com >>>> <swar...@nvidia.com>> >>>> >>>> I would rather that the caller handles this. But failing this perhaps a >>>> new function that does it? Is this for the Ethernet use case? >>> >>> >>> >>> Wouldn't all callers of this function simply call the new function? I'm >>> not >>> aware of any case where the code to avoid duplicate names would not be >>> desired. >>> >>> I hit this for the Ethernet case, but I believe it applies to any type of >>> device at all; see another possible trigger case in the commit >>> description. >> >> >> This does not happen with devices from the device tree. It only >> happens with auto-probed devices. Your I2C GPIO example is odd but I'd >> rather solve that by using the device tree node name. > > > DT itself imposes no such rule; node names must be unique only within their > parent node but there's no restriction on identical node names appearing in > different parts of the tree. > > If U-Boot imposes that rule on DT, then there's no way in general that we > can guarantee U-Boot will be able to use standard DTs (i.e. identical to > those used by Linux or any other OS) for any platform; it'd be another > change someone would need to make to transform a DT to be "U-Boot > compatible", which rather reduces a potential benefit of DT for U-Boot; > being able to just drop a DT in and have it work.
U-Boot does not impose a rule. If you want duplicate device names you can have them. I think it is bad practice though. > > It would be possible for U-Boot to decouple its internal device name from > the DT node name. In which case, your statement would work. However, I don't > think that's the case at the moment, and in fact it's effectively what this > patch is doing, although admittedly there are other ways of doing this. Anyway I believe my point stands. Whereas users can edit the device tree and avoid conflicts they cannot do this with auto-probed devices. So for that case we should have a way of allocating a name before calling device_bind(). Regards, Simon _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
