• Thomas Zimmermann's avatar
    drm/fb-helper: Map DRM client buffer only when required · 87e281f8
    Thomas Zimmermann authored
    This patch changes DRM clients to not map the buffer by default. The
    buffer, like any buffer object, should be mapped and unmapped when
    needed.
    
    An unmapped buffer object can be evicted to system memory and does
    not consume video ram until displayed. This allows to use generic fbdev
    emulation with drivers for low-memory devices, such as ast and mgag200.
    
    This change affects the generic framebuffer console. HW-based consoles
    map their console buffer once and keep it mapped. Userspace can mmap this
    buffer into its address space. The shadow-buffered framebuffer console
    only needs the buffer object to be mapped during updates. While not being
    updated from the shadow buffer, the buffer object can remain unmapped.
    Userspace will always mmap the shadow buffer.
    
    v2:
    	* change DRM client to not map buffer by default
    	* manually map client buffer for fbdev with HW framebuffer
    Signed-off-by: default avatarThomas Zimmermann <tzimmermann@suse.de>
    Reviewed-by: default avatarNoralf Trønnes <noralf@tronnes.org>
    Link: https://patchwork.freedesktop.org/patch/315830/Signed-off-by: default avatarGerd Hoffmann <kraxel@redhat.com>
    87e281f8
drm_client.c 11.8 KB