drm/aperture: Add infrastructure for aperture ownership
Platform devices might operate on firmware framebuffers, such as VESA or EFI. Before a native driver for the graphics hardware can take over the device, it has to remove any platform driver that operates on the firmware framebuffer. Aperture helpers provide the infrastructure for platform drivers to acquire firmware framebuffers, and for native drivers to remove them later on. It works similar to the related fbdev mechanism. During initialization, the platform driver acquires the firmware framebuffer's I/O memory and provides a callback to be removed. The native driver later uses this information to remove any platform driver for it's framebuffer I/O memory. The aperture removal code is integrated into the existing code for removing conflicting framebuffers, so native drivers use it automatically. v5: * fix build error introduced by rebasing v4 * fix typo in documentation v4: * hide detach callback in implementation (Daniel) * documentation fixes v3: * rebase onto existing aperture infrastructure * release aperture from list during detach; fix dangling apertures * don't export struct drm_aperture * document struct drm_aperture_funcs v2: * rename plaform helpers to aperture helpers * tie to device lifetime with devm_ functions * removed unsued remove() callback * rename kickout to detach * make struct drm_aperture private * rebase onto existing drm_aperture.h header file * use MIT license only for simplicity * documentation Signed-off-by:Thomas Zimmermann <tzimmermann@suse.de> Acked-by:
Daniel Vetter <daniel.vetter@ffwll.ch> Acked-by:
Maxime Ripard <maxime@cerno.tech> Tested-by:
nerdopolis <bluescreen_avenger@verizon.net> Link: https://patchwork.freedesktop.org/patch/msgid/20210430105840.30515-4-tzimmermann@suse.de
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