[Intel-gfx] [PATCH 09/16] drm/todo: Add tinydrm refactoring ideas

[Daniel Vetter]

Discussed with Noralf on the list a bit.

An open question is tinydrm vs. drm_panel, but until we have a clear
idea what's really needed in that space, I think it's best to just
move forward with what we have.

Cc: Noralf Trønnes <noralf at tronnes.org>
Signed-off-by: Daniel Vetter <daniel.vetter at intel.com>
---
 Documentation/gpu/todo.rst | 70 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 70 insertions(+)

diff --git a/Documentation/gpu/todo.rst b/Documentation/gpu/todo.rst
index 7dc6de07a3bc..479bb040f6d4 100644
--- a/Documentation/gpu/todo.rst
+++ b/Documentation/gpu/todo.rst
@@ -99,6 +99,30 @@ events for atomic commits correctly. But fixing these bugs is good anyway.
 
 Contact: Daniel Vetter, respective driver maintainers
 
+Better manual-upload support for atomic
+---------------------------------------
+
+This would be especially useful for tinydrm:
+
+- Add a struct drm_rect dirty_clip to drm_crtc_state. When duplicating the
+  crtc state, clear that to the max values, x/y = 0 and w/h = MAX_INT, in
+  __drm_atomic_helper_crtc_duplicate_state().
+
+- Move tinydrm_merge_clips into drm_framebuffer.c, dropping the tinydrm_
+  prefix ofc and using drm_fb_. drm_framebuffer.c makes sense since this
+  is a function useful to implement the fb->dirty function.
+
+- Create a new drm_fb_dirty function which does essentially what e.g.
+  mipi_dbi_fb_dirty does. You can use e.g. drm_atomic_helper_update_plane as the
+  template. But instead of doing a simple full-screen plane update, this new
+  helper also sets crtc_state->dirty_clip to the right coordinates. And of
+  course it needs to check whether the fb is actually active (and maybe where),
+  so there's some book-keeping involved. There's also some good fun involved in
+  scaling things appropriately. For that case we might simply give up and
+  declare the entire area covered by the plane as dirty.
+
+Contact: Noralf Trønnes, Daniel Vetter
+
 Fallout from atomic KMS
 -----------------------
 
@@ -313,5 +337,51 @@ Contact: Daniel Vetter
 Driver Specific
 ===============
 
+tinydrm
+-------
+
+Tinydrm is the helper driver for really simple fb drivers. The goal is to make
+those drivers as simple as possible, so lots of room for refactoring:
+
+- backlight helpers, probably best to put them into a new drm_backlight.c.
+  This is because drivers/video is de-facto unmaintained. We could also
+  move drivers/video/backlight to drivers/gpu/backlight and take it all
+  over within drm-misc, but that's more work.
+
+- spi helpers, probably best put into spi core/helper code. Thierry said
+  the spi maintainer is fast&reactive, so shouldn't be a big issue.
+
+- extract the mipi-dbi helper (well, the non-tinydrm specific parts at
+  least) into a separate helper, like we have for mipi-dsi already. Or follow
+  one of the ideas for having a shared dsi/dbi helper, abstracting away the
+  transport details more.
+
+- tinydrm_lastclose could be drm_fb_helper_lastclose. Only thing we need
+  for that is to store the drm_fb_helper pointer somewhere in
+  drm_device->mode_config. And then we could roll that out to all the
+  drivers.
+
+- tinydrm_gem_cma_prime_import_sg_table should probably go into the cma
+  helpers, as a _vmapped variant (since not every driver needs the vmap).
+  And tinydrm_gem_cma_free_object could the be merged into
+  drm_gem_cma_free_object().
+
+- tinydrm_fb_create we could move into drm_simple_pipe, only need to add
+  the fb_create hook to drm_simple_pipe_funcs, which would again simplify a
+  bunch of things (since it gives you a one-stop vfunc for simple drivers).
+
+- Quick aside: The unregister devm stuff is kinda getting the lifetimes of
+  a drm_device wrong. Doesn't matter, since everyone else gets it wrong
+  too :-)
+
+- With the fbdev pointer in dev->mode_config we could also make
+  suspend/resume helpers entirely generic, at least if we add a
+  dev->mode_config.suspend_state. We could even provide a generic pm_ops
+  structure with those.
+
+- also rework the drm_framebuffer_funcs->dirty hook wire-up, see above.
+
+Contact: Noralf Trønnes, Daniel Vetter
+
 Outside DRM
 ===========
-- 
2.11.0