Re: [PATCH] i2c-EEPROM: Export memory accessor

[David Daney]

On 10/30/2012 11:51 AM, Pantelis Antoniou wrote:
> Hi David,
>
> On Oct 30, 2012, at 8:46 PM, David Daney wrote:
>
> > On 10/31/2012 08:56 AM, Pantelis Antoniou wrote:
> > > Various platforms need access to the EEPROM in other
> > > places besides their platform registration callbacks.
> > > Export the memory accessor to the i2c_client
> >
> > i2c_clients are *not* intrinsically memory, so adding this to the generic i2c_client structure doesn't really make sense.   What would the semantics of this interface be with respect to temperature sensors and GPIO expanders?
> >
> > NACK.
>
> It's only filled in for EEPROM devices. There's no other I2C memory read interface for kernel clients.


Basically you are tacking on a registery of memory devices to some 
random data structure that has nothing to do with memory.

Instead ...

> > > and implement
> > > it for the at24 driver.
> > >
> > > And before you ask, no, the platform callback can't be used
> > > for anything that depends on DT.
> >
> > Why can't you just allocate (and populate) a struct at24_platform_data for the device if it isn't supplied by whatever created the device?
>
> There are no platform_data in the case of device tree only generic-boards. Everything is configured via the DT and there are
> no callbacks. DT is a purely data driver concept.
>
> I'm open to suggestions on how to read an EEPROM from another kernel client, when there's no such thing as platform_data anymore.

... you need some sort of collection memory devices that can be queried 
by phandle and/or some other handle.

Any device that implements the struct memory_accessor interface could 
add itself to the collection, then code that needs to use the 
memory_accessor interface would look up the proper target for the 
operation by phandle or whatever other handle the system is using.

Similar to how of_phy_find_device() works.

I don't know if it would be possible to create a 'memory_accessor' bus, 
but that is one idea I had.

David Daney


> Regards
>
> -- Pantelis
>
>
>
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