linux-kernel - Re: nvmem: add driver for Microchip 24AA025E48 I2C eeprom / nodeID chip

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Message-ID: <CAMRc=Meer40sHKK5WgKJBQsfB7UhU4jDyahifH9a7SBBGywapw@mail.gmail.com>
Date:   Wed, 24 Jan 2018 17:02:06 +0100
From:   Bartosz Golaszewski <brgl@...ev.pl>
To:     Felix Brack <fb@...c.ch>
Cc:     Andy Shevchenko <andy.shevchenko@...il.com>,
        Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: nvmem: add driver for Microchip 24AA025E48 I2C eeprom / nodeID chip

2018-01-24 16:18 GMT+01:00 Felix Brack <fb@...c.ch>:
>
> On 24.01.2018 16:08, Andy Shevchenko wrote:
>> On Wed, Jan 24, 2018 at 4:23 PM, Felix Brack <fb@...c.ch> wrote:
>>> Hello,
>>>
>>> About three years ago I wrote a driver for Microchip's 24AA025E48 I2C
>>> eeprom/nodeID chip. At that time I placed the source files in
>>> drivers/misc/eeprom. I never posted the code.
>>> I now plan to rewrite the driver from scratch. Is it correct to place
>>> the source code in drivers/nvmem and is there a special mailing list to
>>> which the patch should be posted when ready?
>>>
>>> many thanks and kind regards, Felix
>>
>> Does the existing driver [1] work for you (if you add ID there)?
>>
>> [1]: at24
>>
> Yes it does. Actually the driver I wrote 3 years ago is based on the
> at24 driver. Lot's of code in my driver originates directly from the
> at24 driver.
>
> --
> regards Felix

Just from looking at the doc - it seems that it's a variant of
24mac402. You should be able to access the memory block by
instantiating an 'atmel,24c02' device. As for the EUI-48 block -
current at24 driver will not work as the MAC is located at a different
offset in this chip. We need to figure out a portable way to specify
the addresses of such special blocks (same with the serial number) in
the at24 driver.

Anyways - don't write your own driver for that, just make sure at24 works.

Thanks,
Bartosz