Add support for displays that have a register interface and can be operated using a simple vtable.
I have looked through the staging/fbtft drivers and it seems that, except the MIPI controllers, most if not all controllers are operated through a register. And since most controllers have more than one bus interface option, regmap seems like a good choice to describe the interface (tested[1,2]). MIPI DCS can't be represented using regmap since some commands doesn't have a parameter. That would be like a register without a value, which doesn't make sense.
In my second RFC of tinydrm I used drm_panel to decribe the panels since it was a good match to the fbtft displays. I was then told that drm_panel wasn't supposed to used like that, so I dropped it and have tried to use the drm_simple_display_pipe_funcs vtable directly. This hasn't been all successful, since I ended up using devm_add_action() to power down the controller at the right time. Thierry Reding wasn't happy with this and suggested "to add an explicit callback somewhere". My solution has been to copy the drm_panel_funcs vtable. Since I now have a vtable, I also added a callback to flush the framebuffer. So presumably all the fbtft drivers can now be operated through the tinydrm_panel_funcs vtable.
After having done this the question arises: Why not extend tinydrm_device instead of subclassing it?
The benefit of subclassing is that it keeps the door open for drivers that can use tinydrm_device, but not tinydrm_panel. But I don't know of such a driver now, then again who knows what the future brings. Something that might or might not happen isn't a good reason, so it seems that I want it this way because I just like it. And it's easy to merge the two should it be that no one uses tinydrm_device directly three years down the line. But I'm actually not sure what's best.
To recap:
tinydrm_device - Combines drm_simple_display_pipe with CMA backed framebuffer and fbdev. - Optional pipe setup with a connector with one mode, but the driver can do it's own.
tinydrm_panel - All drm operations are distilled down to tinydrm_panel_funcs. - Some common driver properties
Noralf.
[1] https://github.com/notro/tinydrm/blob/master/tinydrm-ili9325.c [2] https://github.com/notro/tinydrm/blob/master/fb_ili9325.c
Noralf Trønnes (5): drm/tinydrm: Add tinydrm_rgb565_buf_copy() drm/tinydrm: Add tinydrm_panel abstraction drm/tinydrm/mipi-dbi: Start conversion to tinydrm_panel drm/tinydrm/mi0283qt: Use tinydrm_panel drm/tinydrm/mipi-dbi: Clean up after tinydrm_panel conversion
Documentation/gpu/tinydrm.rst | 12 + drivers/gpu/drm/tinydrm/Kconfig | 1 + drivers/gpu/drm/tinydrm/core/Makefile | 2 +- drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c | 56 ++- drivers/gpu/drm/tinydrm/core/tinydrm-panel.c | 532 +++++++++++++++++++++++++ drivers/gpu/drm/tinydrm/mi0283qt.c | 113 ++---- drivers/gpu/drm/tinydrm/mipi-dbi.c | 246 ++++-------- include/drm/tinydrm/mipi-dbi.h | 35 +- include/drm/tinydrm/tinydrm-helpers.h | 2 + include/drm/tinydrm/tinydrm-panel.h | 153 +++++++ 10 files changed, 867 insertions(+), 285 deletions(-) create mode 100644 drivers/gpu/drm/tinydrm/core/tinydrm-panel.c create mode 100644 include/drm/tinydrm/tinydrm-panel.h
-- 2.10.2