• Brian Starkey's avatar
    drm: Add writeback connector type · 935774cd
    Brian Starkey authored
    Writeback connectors represent writeback engines which can write the
    CRTC output to a memory framebuffer. Add a writeback connector type and
    related support functions.
    
    Drivers should initialize a writeback connector with
    drm_writeback_connector_init() which takes care of setting up all the
    writeback-specific details on top of the normal functionality of
    drm_connector_init().
    
    Writeback connectors have a WRITEBACK_FB_ID property, used to set the
    output framebuffer, and a WRITEBACK_PIXEL_FORMATS blob used to expose the
    supported writeback formats to userspace.
    
    When a framebuffer is attached to a writeback connector with the
    WRITEBACK_FB_ID property, it is used only once (for the commit in which
    it was included), and userspace can never read back the value of
    WRITEBACK_FB_ID. WRITEBACK_FB_ID can only be set if the connector is
    attached to a CRTC.
    
    Changes since v1:
     - Added drm_writeback.c + documentation
     - Added helper to initialize writeback connector in one go
     - Added core checks
     - Squashed into a single commit
     - Dropped the client cap
     - Writeback framebuffers are no longer persistent
    
    Changes since v2:
     Daniel Vetter:
     - Subclass drm_connector to drm_writeback_connector
     - Relax check to allow CRTC to be set without an FB
     - Add some writeback_ prefixes
     - Drop PIXEL_FORMATS_SIZE property, as it was unnecessary
     Gustavo Padovan:
     - Add drm_writeback_job to handle writeback signalling centrally
    
    Changes since v3:
     - Rebased
     - Rename PIXEL_FORMATS -> WRITEBACK_PIXEL_FORMATS
    
    Chances since v4:
     - Embed a drm_encoder inside the drm_writeback_connector to
       reduce the amount of boilerplate code required from the drivers
       that are using it.
    
    Changes since v5:
     - Added Rob Clark's atomic_commit() vfunc to connector helper
       funcs, so that writeback jobs are committed from atomic helpers
     - Updated create_writeback_properties() signature to return an
       error code rather than a boolean false for failure.
     - Free writeback job with the connector state rather than when
       doing the cleanup_work()
    
    Changes since v7:
     - fix extraneous use of out_fence that is only introduced in a
       subsequent patch.
    
    Changes since v8:
     - whitespace changes pull from subsequent patch
    
    Changes since v9:
     - Revert the v6 changes that free the writeback job in the connector
       state cleanup and return to doing it in the cleanup_work() function
    Signed-off-by: default avatarBrian Starkey <brian.starkey@arm.com>
    [rebased and fixed conflicts]
    Signed-off-by: default avatarMihail Atanassov <mihail.atanassov@arm.com>
    [rebased and added atomic_commit() vfunc for writeback jobs]
    Signed-off-by: default avatarRob Clark <robdclark@gmail.com>
    Signed-off-by: default avatarLiviu Dudau <liviu.dudau@arm.com>
    Reviewed-by: default avatarEric Anholt <eric@anholt.net>
    Link: https://patchwork.freedesktop.org/patch/229037/
    935774cd
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