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"Pre-multiplied" is the default pixel blend mode for KMS/DRM, as documented in supported_modes of drm_plane_create_blend_mode_property(): https://cgit.freedesktop.org/drm/drm-misc/tree/drivers/gpu/drm/drm_blend.c In this mode, both 'pixel alpha' and 'plane alpha' participate in the calculation, as described by the pixel blend mode formula in KMS/DRM documentation: out.rgb = plane_alpha * fg.rgb + (1 - (plane_alpha * fg.alpha)) * bg.rgb Considering the blend config mechanisms we have in the driver so far, the alpha mode that better fits this blend mode is the _PER_PIXEL_ALPHA_COMBINED_GLOBAL_GAIN, where the value for global_gain is the plane alpha (global_alpha). With this change, alpha property stops to be ignored. It also addresses Bug: https://gitlab.freedesktop.org/drm/amd/-/issues/1734 v2: * keep the 8-bit value for global_alpha_value (Nicholas) * correct the logical ordering for combined global gain (Nicholas) * apply to dcn10 too (Nicholas) Signed-off-by: Melissa Wen <mwen@igalia.com> Tested-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com> Reviewed-by: Harry Wentland <harry.wentland@amd.com> Tested-by: Simon Ser <contact@emersion.fr> Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.