[PATCH v2 2/6] drm/fb-helper: Map DRM client buffer only when required

Noralf Trønnes
Sun, 07 Jul 2019 14:25:32 -0000

Den 05.07.2019 11.26, skrev Thomas Zimmermann:
> 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: Thomas Zimmermann <tzimmermann at suse.de>
> ---

Reviewed-by: Noralf Tr?nnes <noralf at tronnes.org>