[PATCH] drm/fb-helper: Blacklist writeback when adding connectors to fbdev

[Maxime Ripard]

On Thu, Nov 15, 2018 at 05:32:48PM +0100, Paul Kocialkowski wrote:
> Writeback connectors do not produce any on-screen output and require
> special care for use. Such connectors are hidden from enumeration in
> DRM resources by default, but they are still picked-up by fbdev.
> This makes rather little sense since fbdev is not really adapted for
> dealing with writeback.
> 
> Moreover, this is also a source of issues when userspace disables the
> CRTC (and associated plane) without detaching the CRTC from the
> connector (which is hidden by default). In this case, the connector is
> still using the CRTC, leading to am "enabled/connectors mismatch" and
> eventually the failure of the associated atomic commit. This situation
> happens with VC4 testing under IGT GPU Tools.
> 
> Filter out writeback connectors in the fbdev helper to solve this.
> 
> Signed-off-by: Paul Kocialkowski <paul.kocialkowski at bootlin.com>

Reviewed-by: Maxime Ripard <maxime.ripard at bootlin.com>
Tested-by: Maxime Ripard <maxime.ripard at bootlin.com>

Thanks!
Maxime

-- 
Maxime Ripard, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com
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