Re: [PATCH v4 01/11] drm/colorop: Add DRM_COLOROP_FIXED_MATRIX

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] Validation check for a 64-bit bitmask on 32-bit platforms incorrectly uses the 32-bit `BIT()` macro, causing upper bits to be silently ignored.
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--- Patch [1]: [PATCH v4 01/11] drm/colorop: Add DRM_COLOROP_FIXED_MATRIX ---
commit e2a1cc91ee8bca2062d87fc6c62ee5b47046aaf8
Author: Chaitanya Kumar Borah <chaitanya.kumar.borah@intel.com>
Subject: drm/colorop: Add DRM_COLOROP_FIXED_MATRIX

This commit introduces DRM_COLOROP_FIXED_MATRIX, a new colorop type
representing hardware that performs a fixed matrix operation. It adds a new
FIXED_MATRIX_TYPE enum property to select predefined hardware modes instead
of using programmable coefficients.

> diff --git a/drivers/gpu/drm/drm_colorop.c b/drivers/gpu/drm/drm_colorop.c
> index 682fcc6515259..e7ccf7d053b89 100644
> --- a/drivers/gpu/drm/drm_colorop.c
> +++ b/drivers/gpu/drm/drm_colorop.c
[ ... ]
> +int drm_plane_colorop_fixed_matrix_init(struct drm_device *dev, struct drm_colorop *colorop,
> +					struct drm_plane *plane,
> +					const struct drm_colorop_funcs *funcs,
> +					u64 supported_fm, uint32_t flags)
> +{
[ ... ]
> +	if (!supported_fm) {
> +		drm_err(dev,
> +			"No supported FM type op for new Fixed Matrix colorop on [PLANE:%d:%s]\n",
> +			plane->base.id, plane->name);
> +		return -EINVAL;
> +	}
> +
> +	if ((supported_fm & -BIT(DRM_COLOROP_FM_COUNT)) != 0) {

[Severity: Medium]
Since supported_fm is a u64, will this check properly mask the upper 32 bits on
32-bit platforms where BIT() evaluates to a 32-bit unsigned long?

When -BIT(DRM_COLOROP_FM_COUNT) is promoted to 64 bits for the bitwise AND, it
will be zero-extended, causing the upper 32 bits of the mask to be zero. This
could allow invalid upper bits in supported_fm to pass validation silently.

Should this use BIT_ULL() instead?

> +		drm_err(dev, "Unknown Fixed Matrix provided on [PLANE:%d:%s]\n",
> +			plane->base.id, plane->name);
> +		return -EINVAL;
> +	}

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Sashiko AI review · https://sashiko.dev/#/patchset/20260722134607.136293-1-harry.wentland@amd.com?part=1