[PATCH 2/3] OMAP2+ devices add mac address allocation register api

Tony Lindgren tony at atomide.com
Fri Jun 29 09:55:59 EDT 2012

* Arnd Bergmann <arnd at arndb.de> [120629 06:50]:
> On Friday 29 June 2012, Tony Lindgren wrote:
> > * Andy Green <andy.green at linaro.org> [120629 03:12]:
> > > >2. Is this really how we want to pass the board generated mac addresses
> > > >    and other dynamically generated data to the drivers that are device
> > > >    tree based?
> > > 
> > > The issue is that both these busses have an async probe, in the case
> > > of USB stack the maintainer was not interested last year in adding
> > > platform data.  Maybe it changed but that's my understanding.
> > 
> > OK, I'd like to hear Arnds comments on the #2 above too as this is
> > a more generic issue.
> In case we have a device tree, we should just be using the USB binding
> to find the specific device node, and add the property there. Then
> the device driver can use of_get_mac_address() on the usb device itself.

But would you generate the mac address then in the bootloader already?
> I'm not sure what it takes to add the link for the device node in the
> usb probing code, but my feeling is that it's not too hard.
> Right now, USB is probed entirely without DT, so the patch is about
> the best we can do.

Right, but that still assumes a static mac from the bootloader unless
we do a generic driver as below? Or do you have some other ideas?
> > > >3. What about mac address in board-generic.c when booting panda with
> > > >    device tree?
> > > 
> > > I don't mind adapting it for that case.
> > 
> > Just to try to think about some alternatives, how about something like
> > this: This all could be a driver called soft-mac or something that does
> > what your patches are doing. Except then it would be completely generic
> > and would be able to take device names and mac addresses from platform
> > data or from devicetree.
> That driver would be completely generic to all platforms, but be
> very specific to finding the mac address of a device, as opposed to
> other properties.
> I suspect that if we do that, we will still need a way to bind a
> device_node to a usb device for the purpose of finding other
> properties, such as external regulators or clocks that are connected
> to a hardwired USB device.

Yes that generic driver could be gind to a usb device and we could
use deferred probe to wait for the mac address to be available.
> Normally USB tends to just work because the device is expected to
> be hot-pluggable anyway. If the USB device is soldered to the
> board, the hardware designers can take some shortcuts

But that too still depends on the order of loading of the multiple
host controller modules. Beagle has both EHCI and musb.



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