Re: [PATCH v2] i2c: i801: Fix missing Kconfig dependency

[Heiner Kallweit <hkallweit1@gmail.com>]

On 05.04.2024 02:54, Andi Shyti wrote:
> Hi Heiner,
> 
> first of all, thanks for the fast reaction!
> 
> On Thu, Apr 04, 2024 at 10:09:50PM +0200, Heiner Kallweit wrote:
>> The original change adds usage of i2c_root_adapter(), which is
>> implemented in i2c-mux.c. Therefore we can't use the multiplexing
>> if I2C_I801=y and I2C_MUX=m.
> 
> What is wrong with select I2C_MUX?
> 
It would solve the issue, but:
We would uselessly enable I2C_MUX also if I2C_MUX_GPIO or DMI are disabled.
W/o them the mux part in i801 is a no-op. The call to i2c_root_adapter()
is in a conditionally compiled code part, controlled by:

#if IS_ENABLED(CONFIG_I2C_MUX_GPIO) && defined CONFIG_DMI

> And is this covering all the cases?
> 
yes

> Last thing, how have you tested and reproduced the issue?
> 
The CI bot report included a link to the kernel config. So it was easy
to understand the root cause of the issue. I could reproduce it by setting:
I2C_I801=y
I2C_MUX=m
I2C_MUX_GPIO=m
This config was also used to test the fix.

Underlying reason for the issue is that i801 has a code dependency on i2c_mux,
but not on i2c_mux_gpio.

> Thanks,
> Andi
> 
Heiner

>> Handling the dependencies in the code would become unnecessarily
>> complex, therefore create a new config symbol.
>>
>> Fixes: 71b494e043d2 ("i2c: i801: Call i2c_register_spd for muxed child segments")
>> Reported-by: kernel test robot <lkp@intel.com>
>> Closes: https://lore.kernel.org/oe-kbuild-all/202404042206.MjAQC32x-lkp@intel.com/
>> Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>