Re: [PATCH 0/8] drm/fb-helper: Use drm_file to get a dumb framebuffer

Laurent Pinchart
2017-09-13T05:09:56Z

Hi Noralf,

Thank you for the patches.

On Monday, 11 September 2017 17:31:54 EEST Noralf Trønnes wrote:
> Hi,
>
> I want to start out by saying that this patchset is low priority for me
> and if no one has interest or time to review this, that is just fine. I
> was in the flow and just typed it out.
>
> This patchset adds a way for fbdev emulation code to create a
> framebuffer that is backed by a dumb buffer. drm_fb_helper gets a
> drm_file to hang the objects on, drm_framebuffer_create_dumb() creates
> the framebuffer and drm_fb_helper_fini() destroys it.
> I have verified that all cma drivers supports dumb buffers, so
> converting the library should be fine for all.

Stupid question, what does this give us ? The series makes the call stack more
complex (up to a point where I'm getting trouble just following it), what's
the advantage that offsets that ?

With the exception of vmwgfx that does weird things I won't even try to
understand, all drivers seem to use the drm_file object passed to the
.dumb_create() operation just to register the GEM object handle. I wonder
whether a better solution to use .dumb_create() for framebuffer emulation
wouldn't be to move the GEM object handle registration from the .dumb_create()
implementation to its caller in the core.

> A patch by David Herrmann from a year ago made this easy. It was the
> last piece in his work to make it possible to create a drm_file for
> in-kernel use, but it never got merged.
>
> I've cc'ed intel-gfx since that will give CI runs of the core patches if
> I understood Daniel right.
>
> Noralf.
>
> David Herrmann (1):
> drm: provide management functions for drm_file
>
> Noralf Trønnes (7):
> drm/framebuffer: Add drm_framebuffer_create_dumb()
> drm/auth: Export drm_dropmaster_ioctl()
> drm/fb-helper: Allocate a drm_file
> drm/fb-cma-helper: Use drm_framebuffer_create_dumb()
> drm/fb-cma-helper: Drop unnecessary fbdev buffer offset
> drm/tinydrm: Use drm_fbdev_cma_init()
> drm/fb-cma-helper: Remove drm_fbdev_cma_init_with_funcs()
>
> drivers/gpu/drm/drm_auth.c | 1 +
> drivers/gpu/drm/drm_fb_cma_helper.c | 111 ++--------
> drivers/gpu/drm/drm_fb_helper.c | 22 +-
> drivers/gpu/drm/drm_file.c | 323 +++++++++++++++----------
> drivers/gpu/drm/drm_framebuffer.c | 61 ++++++
> drivers/gpu/drm/drm_internal.h | 2 -
> drivers/gpu/drm/tinydrm/core/tinydrm-core.c | 5 +-
> include/drm/drm_auth.h | 2 +
> include/drm/drm_fb_helper.h | 9 +
> include/drm/drm_file.h | 2 +
> include/drm/drm_framebuffer.h | 4 +
> 11 files changed, 305 insertions(+), 237 deletions(-)

--
Regards,

Laurent Pinchart

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