Re: [PATCH v2 2/2] drm/tiny: allow a framebuffer larger than the panel on MIPI DBI drivers

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] drm/sitronix: missed st7735r in max framebuffer size update for MIPI DBI drivers
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commit 50f420ca1ad2ba6dcb54d9452d2d9f6ac5dcbc2d
Author: Jonathan Frazin <frazinjonathan@gmail.com>

drm/tiny: allow a framebuffer larger than the panel on MIPI DBI drivers

This commit raises the max_width and max_height limits to
DRM_SHADOW_PLANE_MAX_WIDTH and DRM_SHADOW_PLANE_MAX_HEIGHT for MIPI DBI
drivers that flush through drm_mipi_dbi_plane_helper_atomic_update(). This
allows userspace to allocate larger framebuffers and pick the displayed
region via the plane source rectangle without scaling.

> Raise the maximums to DRM_SHADOW_PLANE_MAX_WIDTH/HEIGHT (which its
> kerneldoc recommends for shadow-plane drivers) on the drivers that flush
> through the shared drm_mipi_dbi_plane_helper_atomic_update(), so a client
> can allocate a larger framebuffer and pick the displayed region through
> the plane source rectangle - a crop / pan with no scaling, now that
> drm_mipi_dbi honours the source offset (previous patch):
> 
>     ili9341, hx8357d, ili9486, mi0283qt, ili9163, panel-mipi-dbi

[Severity: Medium]
Was the st7735r driver intentionally omitted from this list?

It appears that st7735r also uses DRM_MIPI_DBI_PLANE_HELPER_FUNCS (which
sets drm_mipi_dbi_plane_helper_atomic_update) but continues to restrict the
framebuffer size to the panel dimensions.

In drivers/gpu/drm/sitronix/st7735r.c:st7735r_probe():

	drm->mode_config.min_width = dbidev->mode.hdisplay;
	drm->mode_config.max_width = dbidev->mode.hdisplay;
	drm->mode_config.min_height = dbidev->mode.vdisplay;
	drm->mode_config.max_height = dbidev->mode.vdisplay;

Since it is located in drivers/gpu/drm/sitronix/ rather than
drivers/gpu/drm/tiny/, could it have been overlooked? This omission leaves
the st7735r driver unable to support the crop and pan functionality being
enabled for the other MIPI DBI drivers.

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Sashiko AI review · https://sashiko.dev/#/patchset/20260923195713.88-1-frazinjonathan@gmail.com?part=2