linux-kernel - Re: [PATCH 15/20] drivers/gpu/drm/i915/display: remove I2C_CLASS

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Message-ID: <878r71tudv.fsf@intel.com>
Date:   Mon, 13 Nov 2023 19:50:36 +0200
From:   Jani Nikula <jani.nikula@...ux.intel.com>
To:     Heiner Kallweit <hkallweit1@...il.com>,
        Wolfram Sang <wsa@...nel.org>
Cc:     linux-i2c@...r.kernel.org,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        Tvrtko Ursulin <tvrtko.ursulin@...ux.intel.com>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        intel-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 15/20] drivers/gpu/drm/i915/display: remove
 I2C_CLASS_DDC support

On Mon, 13 Nov 2023, Heiner Kallweit <hkallweit1@...il.com> wrote:
> On 13.11.2023 13:17, Jani Nikula wrote:
>> On Mon, 13 Nov 2023, Heiner Kallweit <hkallweit1@...il.com> wrote:
>>> After removal of the legacy EEPROM driver and I2C_CLASS_DDC support in
>>> olpc_dcon there's no i2c client driver left supporting I2C_CLASS_DDC.
>>> Class-based device auto-detection is a legacy mechanism and shouldn't
>>> be used in new code. So we can remove this class completely now.
>> 
>> So this is copy-pasted to all commits and the cover letter, but please
>> do explain why there are no functional changes here (or are there?),
>> without me having to go through the i2c stack and try to find the
>> commits alluded to in "After removal of the legacy ...".
>> 
> Legacy eeprom driver was marked deprecated 4 yrs ago with:
> 3079b54aa9a0 ("eeprom: Warn that the driver is deprecated")
> Now it has been removed with:
> 0113a99b8a75 ("eeprom: Remove deprecated legacy eeprom driver")
>
> Declaration of I2C_CLASS_DDC support is a no-op now, so there's
> no functional change in this patch.
>
> If loaded manually, the legacy eeprom driver exposed the DDC EEPROM
> to userspace. If this functionality is needed, then now the DDC
> EEPROM has to be explicitly instantiated using at24.
>
> See also:
> https://docs.kernel.org/i2c/instantiating-devices.html

I'll take your word for it. Though none of the documentation I can find
say that setting the class is legacy or deprecated or should be
avoided. *shrug*.

Acked-by: Jani Nikula <jani.nikula@...el.com>


>
>
>> What does this mean?
>> 
>> 
>> BR,
>> Jani.
>> 
> Heiner
>
>> 
>>>
>>> Preferably this series should be applied via the i2c tree.
>>>
>>> Signed-off-by: Heiner Kallweit <hkallweit1@...il.com>
>>>
>>> ---
>>>  drivers/gpu/drm/i915/display/intel_gmbus.c |    1 -
>>>  drivers/gpu/drm/i915/display/intel_sdvo.c  |    1 -
>>>  2 files changed, 2 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/i915/display/intel_gmbus.c b/drivers/gpu/drm/i915/display/intel_gmbus.c
>>> index 40d7b6f3f..e9e4dcf34 100644
>>> --- a/drivers/gpu/drm/i915/display/intel_gmbus.c
>>> +++ b/drivers/gpu/drm/i915/display/intel_gmbus.c
>>> @@ -899,7 +899,6 @@ int intel_gmbus_setup(struct drm_i915_private *i915)
>>>  		}
>>>  
>>>  		bus->adapter.owner = THIS_MODULE;
>>> -		bus->adapter.class = I2C_CLASS_DDC;
>>>  		snprintf(bus->adapter.name,
>>>  			 sizeof(bus->adapter.name),
>>>  			 "i915 gmbus %s", gmbus_pin->name);
>>> diff --git a/drivers/gpu/drm/i915/display/intel_sdvo.c b/drivers/gpu/drm/i915/display/intel_sdvo.c
>>> index a636f42ce..5e64d1baf 100644
>>> --- a/drivers/gpu/drm/i915/display/intel_sdvo.c
>>> +++ b/drivers/gpu/drm/i915/display/intel_sdvo.c
>>> @@ -3311,7 +3311,6 @@ intel_sdvo_init_ddc_proxy(struct intel_sdvo_ddc *ddc,
>>>  	ddc->ddc_bus = ddc_bus;
>>>  
>>>  	ddc->ddc.owner = THIS_MODULE;
>>> -	ddc->ddc.class = I2C_CLASS_DDC;
>>>  	snprintf(ddc->ddc.name, I2C_NAME_SIZE, "SDVO %c DDC%d",
>>>  		 port_name(sdvo->base.port), ddc_bus);
>>>  	ddc->ddc.dev.parent = &pdev->dev;
>>>
>> 
>

-- 
Jani Nikula, Intel