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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <6f924890-a5a0-48b4-973d-3c0f88b0d294@gmail.com>
Date:   Mon, 13 Nov 2023 13:32:07 +0100
From:   Heiner Kallweit <hkallweit1@...il.com>
To:     Jani Nikula <jani.nikula@...ux.intel.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 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


> 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;
>>
>