Re: [PATCH v2] of_net: Implement of_get_nvmem_mac_address helper

[Mike Looijmans]

On 26-03-18 19:05, Florian Fainelli wrote:
> On 03/26/2018 09:58 AM, David Miller wrote:
> > From: Mike Looijmans <mike.looijmans@xxxxxxxx>
> > Date: Mon, 26 Mar 2018 08:41:29 +0200
> >
> > > It's common practice to store MAC addresses for network interfaces into
> > > nvmem devices. However the code to actually do this in the kernel lacks,
> > > so this patch adds of_get_nvmem_mac_address() for drivers to obtain the
> > > address from an nvmem cell provider.
> > >
> > > This is particulary useful on devices where the ethernet interface cannot
> > > be configured by the bootloader, for example because it's in an FPGA.
> > >
> > > Tested by adapting the cadence macb driver to call this instead of
> > > of_get_mac_address().
> > >
> > > Signed-off-by: Mike Looijmans <mike.looijmans@xxxxxxxx>
> > > ---
> > > v2: Use of_nvmem_cell_get to avoid needing the assiciated device
> > >      Use void* instead of char*
> > >      Add devicetree binding doc
> >
> > Like Andrew, I think you should add a new interface for getting the MAC
> > address from nvmem.
> >
> > And drivers can call both of them if they want OF device tree and
> > NVMEM probing for MAC addresses.
> >
> > Later you can add a consolidated interface, if necessary, which does
> > both and also take a reference to the MAC address buffer of the driver
> > in order to deal with the resource allocation issues.
>
> Agreed, also, how does this fit with Alban's patch series here:

Ok, makes sense. I'll cook up a v3.

> https://lkml.org/lkml/2018/3/24/312
>
> do you depend on those changes at all?

As far as I can tell, there's no dependency, I'm adding an nvmem 
"consumer" while Alban's patch adds a "provider". I'm mainly interested 
in storing the MAC address into an I2C EEPROM, which you can also buy 
with a pre-programmed MAC address in the first 6 bytes, so there's no 
production cost for managing that.


Alban's patch might some day collide with my idea of making hardware 
that has some unique ID into nvmem providers, like 1-wire chips, some 
NOR flash chips (there's the conflict) and various other devices. That 
would allow a board to obtain a random yet constant MAC address without 
any additional hardware. I'll cross that bridge when I find it.


--
Mike Looijmans