Re: [PATCH] eeprom: add non-cached sysfs read access to EEPROM data

[Petri Gynther <pgynther-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>]

Greg,

It is up to the userspace app to decide whether to use cached
("eeprom") or non-cached ("eeprom-nc") sysfs interface.

Example: SFP module
It exposes two 256-byte EEPROM(-like) devices at 0x50 and 0x51.
0x50 is static vendor/part info and can be cached.
0x51 is real-time diagnostic data and cannot be cached.

Unfortunately, 0x51 does not have any identifying bits telling us that
it is real-time data.
(If it did, it would be easy to check and remember this when 0x51 is probed.)

-- Petri

On Tue, Sep 1, 2009 at 4:39 PM, Greg KH<greg-U8xfFu+wG4EAvxtiuMwx3w@public.gmane.org> wrote:
> On Tue, Sep 01, 2009 at 04:15:00PM -0700, Petri Gynther wrote:
>> Add "eeprom-nc" sysfs attribute to provide non-cached read access
>> to EEPROM data. This is needed because some EEPROM-like devices
>> contain constantly changing real-time diagnostic data that cannot
>> be cached in kernel memory.
>
> How are we going to know which attribute to use?
>
> For all new sysfs attributes, you have to add a Documentation/ABI/ file
> as well, care to do that here?
>
> thanks,
>
> greg k-h
>