linux-kernel - Re: [PATCH 2/6] nvmem: Add backwards compatibility support for older EEPROM drivers.

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Date:	Tue, 15 Dec 2015 10:04:38 +0000
From:	Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
To:	Wolfram Sang <wsa@...-dreams.de>, Andrew Lunn <andrew@...n.ch>
CC:	GregKH <greg@...ah.com>, maxime.ripard@...e-electrons.com,
	broonie@...nel.org, vz@...ia.com, afd@...com,
	linux-kernel@...r.kernel.org,
	Pantelis Antoniou <pantelis.antoniou@...sulko.com>
Subject: Re: [PATCH 2/6] nvmem: Add backwards compatibility support for older
 EEPROM drivers.



On 11/12/15 13:03, Wolfram Sang wrote:
> On Tue, Dec 08, 2015 at 03:05:07PM +0100, Andrew Lunn wrote:
>> Older drivers made an 'eeprom' file available in the /sys device
>> directory. Have the NVMEM core provide this to retain backwards
>> compatibility.
>>
>> Signed-off-by: Andrew Lunn <andrew@...n.ch>
>> ---
>>   drivers/nvmem/Kconfig          |  7 ++++
>>   drivers/nvmem/core.c           | 75 +++++++++++++++++++++++++++++++++++++++---
>>   include/linux/nvmem-provider.h | 10 ++++++
>>   3 files changed, 88 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/nvmem/Kconfig b/drivers/nvmem/Kconfig
>> index bc4ea585b42e..b4e79ba7d502 100644
>> --- a/drivers/nvmem/Kconfig
>> +++ b/drivers/nvmem/Kconfig
>> @@ -13,6 +13,13 @@ menuconfig NVMEM
>>   	  If unsure, say no.
>>
>>   if NVMEM
>> +config NVMEM_COMPAT
>> +       bool "Enable /sys compatibility with old eeprom drivers"
>> +       help
>> +	 Older EEPROM drivers, such as AT24, AT25, provide access to
>> +	 the eeprom via a file called "eeprom" in /sys under the
>> +	 device node. Enabling this option makes the NVMEM core
>> +	 provide this file to retain backwards compatibility
>
> I don't like this being a Kconfig option TBH. In most cases, when I read
> "retain backwards compatibility" in Kconfig help texts, I keep the
> option activated because I don't know the details when exactly it is
> safe to disable it. Plus, we have too many Kconfig symbols already.
>
+1 for not adding new Kconfig here.


> I suggest to add this flag to nvmem_config and let the old eeprom
> drivers always set this flag because they need to provide this file for
> some more time, if not forever. New drivers using the nvmem_layer will
> probably not want to set this.

yes, thats my view to, we should move the flag to nvmem_config and let 
nvmem_register() do what it wants with it, this would avoid adding new 
api too.
>
> BTW how does this NVMEM framework relate to the memory_accessor
> framework. Can it be used to replace it? I think we should keep the
> number of eeprom interfaces at a sane level, preferably 1 ;)

Non DT users can still get access to nvmem by passing nvmem provider 
name to nvmem_device_get(), this should be able to replace the need of 
memory_accessor.

--srini


>
> Also adding Pantelis to CC who also submitted at24 NVMEM support a while
> ago.
>
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