Hi Javier Am 07.04.22 um 09:43 schrieb Javier Martinez Canillas:
On 4/6/22 21:08, Thomas Zimmermann wrote: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@xxxxxxx> ---[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.I do not. But I wonder if the problem here is the usage of select rather than depends and if with the later the original design could still be achieved...
With 'depends DRM_DISPLAY_HELPER' users would need to explictly enable DRM_DISPLAY_HELPER, I think.
But yes, probably the only way to prevent that issue is to make the drivers to explicitly select both DRM_DISPLAY_HELPER and respective helpers symbol.
I'll remake the patches with the new style.I think another idea that could work is to use an intermediate symbol. For DP, drivers would select the tristate DP_HELPER, which in turn selects tristate DISPLAY_HELPER and boolean DISPLAY_DP_HELPER. But this would require a 'useless' symbol DP_HELPER only for convenience. It's an even less optimal solution, it seems.
Best regards Thomas
-- Best regards, Javier Martinez Canillas Linux Engineering Red Hat
-- 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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