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No more new fbdev drivers, please

DISCUSSION Kamil Lulko 4 participants 4 messages Sep 25, 2015 – Sep 26, 2015 Framebuffer layer

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#0 lore raw

Hi,

Quoted 2 lines

fbdev is (more or less) maintained, but it's a deprecated framework. All new Linux display drivers should be done on DRM.

What about no-mmu platforms? DRM has a big fat MMU dependency in the kconfig, is there a way to write DRM driver for such devices?

/Kamil

#1 lore raw
Quoted 7 lines · Kamil Lulko

Hi,

Quoted 2 lines

fbdev is (more or less) maintained, but it's a deprecated framework. All new Linux display drivers should be done on DRM.

What about no-mmu platforms? DRM has a big fat MMU dependency in the kconfig, is there a way to write DRM driver for such devices?

I guess not.

Then again, I don't see why DRM would have a hard dependency to MMU, if the work is done to make DRM work optionally without MMU. How much work that is, I have no idea.

Tom

#2 lore raw
Quoted 8 lines · Tomi Valkeinen
Quoted 5 lines · Kamil Lulko

Hi,

Quoted 2 lines

fbdev is (more or less) maintained, but it's a deprecated framework. All new Linux display drivers should be done on DRM.

Quoted 8 lines
Quoted 2 lines

What about no-mmu platforms? DRM has a big fat MMU dependency in the kconfig, is there a way to write DRM driver for such devices?

I guess not.

Then again, I don't see why DRM would have a hard dependency to MMU, if the work is done to make DRM work optionally without MMU. How much work that is, I have no idea.

We have plenty drivers in drm without hw mmu, and yeah there's probably no reason at all why the drm subsystem has a hard depency on cpu MMUs. Might be some #ifdef fallout that needs to be done, but there shouldn't be anything fundamental. Maybe the old dri1 days code has something, but that's all historical cruft anyway.
-Daniel

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Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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#3 lore raw
In reply to Kamil Lulko
Quoted 6 lines · Kamil Lulko
Quoted 2 lines

fbdev is (more or less) maintained, but it's a deprecated framework. All new Linux display drivers should be done on DRM.

What about no-mmu platforms? DRM has a big fat MMU dependency in the kconfig, is there a way to write DRM driver for such devices?

That would indeed be a showstopper...

I dropped the dependency, and gave it a quick try for m68knommu. Seems like DRM currently needs pgprot_writecombine() and pte_wrprotect(). Probably that can be fixed easily.

Gr{oetje,eeting}s,

Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- [email protected]

In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds