[PATCH 3/8] drm/display: Introduce a DRM display-helper module

[Thomas Zimmermann]

Hi Javier

Am 30.03.22 um 11:23 schrieb Javier Martinez Canillas:
> On 3/22/22 20:27, Thomas Zimmermann wrote:
>> Replace the DP-helper module with a display-helper module. Update
>> all related Kconfig and Makefile rules.
>>
>> Besides the existing code for DisplayPort, the new module will
>> contain helpers for other video-output standards, such as HDMI.
>> Drivers will still be able to select the required video-output
>> helpers. Linking all such code into a single module avoids the
>> proliferation of small kernel modules.
>>
>> Signed-off-by: Thomas Zimmermann <tzimmermann at suse.de>
>> ---
> 
> [snip]
> 
>> +config DRM_DISPLAY_HELPER
>> +	tristate
>> +	depends on DRM
>> +	help
>> +	  DRM helpers for display adapters.
>> +
>>   config DRM_DP_HELPER
>>   	tristate
>>   	depends on DRM
>> +	select DRM_DISPLAY_HELPER
>>   	help
>>   	  DRM helpers for DisplayPort.
>>
> 
> I was about to ask why this would still be needed but then re-read the
> commit message that says drivers will still be able to select required
> video-output helpers.
> 
> That makes sense since the fact that all helpers will be in the same module
> would be transparent to drivers.

After some more testing, it turns out to be not so easy. For example, if 
we have DP_HELPER=m and HDMI_HELPER=y, then DISPLAY_HELPER would be 
auto-selected as 'y'. The code for DP_HELPER would not be linked correctly.

I'm going to make drivers select DISPLAY_HELPER and the rsp helpers 
explicitly. The individual helpers would be covered boolean options that 
enable the feature in the display-helper library.

If you know some Kconfig magic to enable the original design, let me know.

Best regards
Thomas


-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Ivo Totev
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