[PATCH v2 0/6] drm/st7571-i2c: add support for grayscale xrgb8888

[Marcus Folkesson <marcus.folkesson@gmail.com>]

The goal with this series is to add support for 2bit grayscale with
the xrgb8888 pixel format for the st7571 display controller.

The first patch only corrects a comment of the pixel format.

The next four patches adds support for inverting pixels. This is
necessary as the connected display may or may not use the "right" (0 =>
black, 1 => white) pixel format expected by the supported formats
(R1/R2/XRGB8888).

The fifth patch adds a helper function (drm_fb_xrgb8888_to_gray2) to
convert xrgb8888 to gray2.

The last path adds support for gray2 in the st7571 driver.
Compare the mono [1] and the gray2 [2] variants of our penguin.

[1] https://www.marcusfolkesson.se/gray2.png
[2] https://www.marcusfolkesson.se/xrgb8888.png

Signed-off-by: Marcus Folkesson <marcus.folkesson@gmail.com>
---
Changes in v2:
- Do not share code between _to_mono() and _to_gray2()
- Correct formatting (remove  "|") in the dt bindings
- Implement support for inverting pixels for st7567
- Link to v1: https://lore.kernel.org/r/20250714-st7571-format-v1-0-a27e5112baff@gmail.com

---
Marcus Folkesson (6):
      drm/st7571-i2c: correct pixel data format description
      dt-bindings: display: sitronix,st7571: add optional inverted property
      dt-bindings: display: sitronix,st7567: add optional inverted property
      drm/st7571-i2c: add support for inverted pixel format
      drm/format-helper: introduce drm_fb_xrgb8888_to_gray2()
      drm/st7571-i2c: add support for 2bit grayscale for XRGB8888

 .../bindings/display/sitronix,st7567.yaml          |   5 +
 .../bindings/display/sitronix,st7571.yaml          |   5 +
 drivers/gpu/drm/drm_format_helper.c                | 108 +++++++++++++++++++++
 drivers/gpu/drm/sitronix/st7571-i2c.c              |  41 ++++----
 include/drm/drm_format_helper.h                    |   4 +
 5 files changed, 144 insertions(+), 19 deletions(-)
---
base-commit: ca2a6abdaee43808034cdb218428d2ed85fd3db8
change-id: 20250520-st7571-format-2ce6badc48c6

Best regards,
-- 
Marcus Folkesson <marcus.folkesson@gmail.com>