Re: [RFC PATCH 0/3] staging: remove fbdev drivers

On 10/12/16 05:27 AM, Benjamin Herrenschmidt wrote:

On Fri, 2016-12-09 at 14:35 +0100, Daniel Vetter wrote:

quoted

quoted

As for multi userspace client, well, swapping an mmap between HW and
memory backing store is a somewhat solved problem already.

Hm, I didn't know that, but then all existing drm drivers have fairly
simplistic fbdev mmap implementations.

Hrm, I though the TTM did it ... I remember talking with Thomas
Hellstrom about that back in the day... you use unmap_mapping_range
to unmap the existing mappings basically so you can take new faults
and route them to a different page, but I can't see a call in there
so maybe he ended up not doing it.

I think he did, it was working fine for userspace mappings when I tried
making radeon use a non-pinned BO for fbdev years ago (the problem was
fbcon potentially trying to access the framebuffer at the most
inconvenient times). There's still ttm_fbdev_mmap, but I'm not sure
everything to make this fully work for userspace fbdev mappings is still
there.


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Earthling Michel Dänzer               |               http://www.amd.com
Libre software enthusiast             |             Mesa and X developer