Re: [PATCH] i2c: mux: reg: Remove class-based device auto-detection support

[Heiner Kallweit <hkallweit1@gmail.com>]

On 20.12.2023 21:45, Wolfram Sang wrote:
> On Wed, Nov 08, 2023 at 07:38:07AM +0100, Heiner Kallweit wrote:
>> Legacy class-based device auto-detection shouldn't be used in new code.
>> Therefore remove support in i2c-mux-reg as long as we don't have a
>> user of this feature yet.
>>
>> Link: https://lore.kernel.org/linux-i2c/a22978a4-88e4-46f4-b71c-032b22321599@gmail.com/
>> Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
> 
> Applied to for-next, thanks!
> 
> I guess i2c-mux-gpio is more difficult because it has users already?
> 
Right. i801 has a special handling for certain Asus server models with
> 8 memory slots where the smbus to the SPD eeproms is gpio-muxed.
I2C_CLASS_HWMON is passed to the child adapters to probe for DIMM
thermal sensors.

For getting rid of the class-based probing we have to:
- Extend i2c_register_spd() for use on muxed smbus segments.
  Then i2c_register_spd() instantiates at24 to handle the SPD eeprom (for DDR3)
- at24 then checks the SPD for an advertised thermal sensor, and instantiates
  jc42 to handle the thermal sensor -> a patch for this has been submitted

The extension of i2c_register_spd() needs some more thoughts.