linux-kernel - Re: [PATCH] eeprom: New ee1004 driver for DDR4 memory

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Message-ID: <CAMRc=McpCp5BQ61B6Gwd2OcuJq_aeT2fqwFRPF7xum-gn4yRXQ@mail.gmail.com>
Date:   Mon, 26 Feb 2018 15:32:35 +0100
From:   Bartosz Golaszewski <brgl@...ev.pl>
To:     Jean Delvare <jdelvare@...e.de>
Cc:     Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Linux I2C <linux-i2c@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] eeprom: New ee1004 driver for DDR4 memory

2018-02-26 15:26 GMT+01:00 Jean Delvare <jdelvare@...e.de>:
> Hi Bartosz,
>
> On Mon, 26 Feb 2018 14:40:42 +0100, Bartosz Golaszewski wrote:
>> 2018-02-26 10:20 GMT+01:00 Jean Delvare <jdelvare@...e.de>:
>> > The EEPROMs which hold the SPD data on DDR4 memory modules are no
>> > longer standard AT24C02-compatible EEPROMs. They are 512-byte EEPROMs
>> > which use only 1 I2C address for data access. You need to switch
>> > between the lower page and the upper page of data by sending commands
>> > on the SMBus.
>> >
>> > Signed-off-by: Jean Delvare <jdelvare@...e.de>
>> > ---
>> >  drivers/misc/eeprom/Kconfig  |   11 +
>> >  drivers/misc/eeprom/Makefile |    1
>> >  drivers/misc/eeprom/ee1004.c |  281 +++++++++++++++++++++++++++++++++++++++++++
>> >  3 files changed, 293 insertions(+)
>>
>> is there any reason not to use regmap as is done currently in at24? It
>> would spare you a lot of code.
>
> No specific reason, just the fact that I never used regmap before so
> the idea did not occur to me. I can give it a try, but my driver is
> already pretty simple so I'm curious if there's really anything to win.
> Let's see.
>

You wouldn't need to check i2c functionalities and could simplify the
read functions.

> Is there any documentation available on how to convert an existing
> driver to use regmap?
>

Take a look at the series from Heiner[1].

> --
> Jean Delvare
> SUSE L3 Support

I'm also seeing that you exported the sysfs eeprom attribute by hand.
I think you should register the driver as nvmem provider and set the
compat flag in nvmem config instead.

Thanks,
Bart

[1] http://patchwork.ozlabs.org/project/linux-i2c/list/?series=15614&state=*