[PATCH v3 0/2] drm/tiny: add support for PIXPAPER 4.26 monochrome e-ink panel

[LiangCheng Wang <zaq14760@gmail.com>]

This patch series adds support for the Mayqueen Pixpaper 4.26
monochrome e-ink display panel, controlled via SPI.

The series includes:
- Device tree binding updates for the Pixpaper 4.26 panel
- A DRM tiny driver implementation for the Pixpaper 4.26 panel
- A MAINTAINERS update for the Pixpaper DRM drivers and binding

The panel supports 800x480 resolution with XRGB8888 framebuffer
input and uses SPI, along with GPIO lines for reset, busy, and
data/command control.

Tested on:
- Raspberry Pi 5 with Linux kernel 7.1.0-rc1

Feedback is welcome.

Signed-off-by: LiangCheng Wang <zaq14760@gmail.com>
---
Changes in v3:
- Keep Conor's Acked-by on the DT binding patch.
- Avoid passing stack and read-only buffers to spi_write().
- Use le32_to_cpu() when reading XRGB8888 pixels.
- Document the panel RAM X direction used during framebuffer conversion.
- Document why busy-wait timeouts remain warning-only.
- Rename the busy-wait helper to pixpaper_wait_for_panel().
- Drop the forward declaration of pixpaper_xrgb8888_to_bw() by moving its
  definition before its first use.
- Use a fixed display mode with drm_connector_helper_get_modes_fixed().
- Drop the redundant mode_config mode_valid callback; resolution is
  validated only by the CRTC mode_valid callback.
- Use drm_err_once() for errors in userspace-triggered update paths.
- Link to v2: https://lore.kernel.org/r/20260526-bar-v2-0-c66df9a840c4@gmail.com

Changes in v2:
- Explain why pixpaper-426m requires a distinct compatible string despite
  sharing the same SPI and GPIO properties with the existing Pixpaper panel.
- Drop the duplicated pixpaper-426m DT binding example.
- Update the binding description for multiple Pixpaper panels.
- Select DRM_GEM_SHMEM_HELPER instead of DRM_GEM_DMA_HELPER for the
  pixpaper-426m driver.
- Link to v1: https://lore.kernel.org/r/20260506-bar-v1-0-12195406f4ef@gmail.com

---
LiangCheng Wang (2):
      dt-bindings: display: mayqueen,pixpaper: add pixpaper-426m
      drm/tiny: add support for PIXPAPER 4.26 monochrome e-ink panel

 .../bindings/display/mayqueen,pixpaper.yaml        |  13 +-
 MAINTAINERS                                        |   3 +-
 drivers/gpu/drm/tiny/Kconfig                       |  16 +
 drivers/gpu/drm/tiny/Makefile                      |   1 +
 drivers/gpu/drm/tiny/pixpaper-426m.c               | 817 +++++++++++++++++++++
 5 files changed, 844 insertions(+), 6 deletions(-)
---
base-commit: a293ec25d59dd96309058c70df5a4dd0f889a1e4
change-id: 20260505-bar-523f2c3f6939

Best regards,
-- 
LiangCheng Wang <zaq14760@gmail.com>