Hi Javier Am 13.05.22 um 13:10 schrieb Javier Martinez Canillas: ...
We already track the memory ranges in drm aperture helpers. We'd need to move the code to a more prominent location (e.g., <linux/aperture.h>) and change fbdev to use it. Sysfb and DT code needs to insert platform devices upon creation. We can then implement the more fancy stuff, such as tracking native-device memory. (And if we ever get to fix all usage of Linux' request-mem-region, we can even move all the functionality there).Agreed. And as mentioned, the race that these patches attempt to fix are for the less common case when a native driver probes but either no generic driver registered a framebuffer yet or the platform device wasn't registered yet. But this can only happen if for example a native driver is built-in but the generic driver is build as a module, which is not the common configuration. What most distros do is the opposite, to have {simple,of,efi,vesa}fb or simpledrm built-in and the native drivers built as modules. So there's no rush to fix this by piling more hacks on top of the ones we already have and instead try to fix it more properly as you suggested.
A first step would be to use DRM's aperture helpers in fbdev. That would be a good idea anyway, as it would simplify both. You already mentioned some API changes to make aperture helpers DRM-independent.
The affected fbdev drivers use platform devices, so this should be easy.Aperture helpers have something like the registration_lock. [1] I don't know if we need to recreate patch 3 for this as well.
If we absolutely need some special detachment handling for fbdev, we can make devm_aperture_aquire() a public interface. The detach helper is provided by the caller.
Best regards Thomas[1] https://elixir.bootlin.com/linux/v5.17.6/source/drivers/gpu/drm/drm_aperture.c#L254 [2] https://elixir.bootlin.com/linux/v5.17.6/source/drivers/gpu/drm/drm_aperture.c#L159
-- 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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