[PATCH v3 7/7] drm: Allow drivers to leave encoder->possible_crtcs==0

[Daniel Vetter]

On Tue, Feb 11, 2020 at 06:22:08PM +0200, Ville Syrjala wrote:
> From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> 
> Let's simplify life of driver by allowing them to leave
> encoder->possible_crtcs unset if they have no restrictions
> in crtc<->encoder linkage. We'll just populate possible_crtcs
> with the full crtc mask when registering the encoder so that
> userspace doesn't have to deal with drivers not populating
> this correctly.
> 
> Cc: Thomas Zimmermann <tzimmermann at suse.de>
> Cc: Daniel Vetter <daniel at ffwll.ch>
> Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
> ---
> We might not actually need/want this, but included it here for
> future reference if that assumption turns out to be wrong.

I think this one is most definitely needed. _Lots_ of drivers get this
toally wrong and just leave the value blank. It's encoded as official
fallback in most userspace compositors.

Reviewed-by: Daniel Vetter <daniel.vetter at ffwll.ch>

> ---
>  drivers/gpu/drm/drm_mode_config.c | 15 ++++++++++++++-
>  include/drm/drm_encoder.h         |  4 ++++
>  2 files changed, 18 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/drm_mode_config.c b/drivers/gpu/drm/drm_mode_config.c
> index 4c1b350ddb95..ce18c3dd0bde 100644
> --- a/drivers/gpu/drm/drm_mode_config.c
> +++ b/drivers/gpu/drm/drm_mode_config.c
> @@ -592,6 +592,17 @@ static u32 full_crtc_mask(struct drm_device *dev)
>  	return crtc_mask;
>  }
>  
> +/*
> + * Make life easy for drivers by allowing them to leave
> + * possible_crtcs unset if there are not crtc<->encoder
> + * restrictions.
> + */
> +static void fixup_encoder_possible_crtcs(struct drm_encoder *encoder)
> +{
> +	if (encoder->possible_crtcs == 0)
> +		encoder->possible_crtcs = full_crtc_mask(encoder->dev);
> +}
> +
>  static void validate_encoder_possible_crtcs(struct drm_encoder *encoder)
>  {
>  	u32 crtc_mask = full_crtc_mask(encoder->dev);
> @@ -608,8 +619,10 @@ void drm_mode_config_validate(struct drm_device *dev)
>  {
>  	struct drm_encoder *encoder;
>  
> -	drm_for_each_encoder(encoder, dev)
> +	drm_for_each_encoder(encoder, dev) {
>  		fixup_encoder_possible_clones(encoder);
> +		fixup_encoder_possible_crtcs(encoder);
> +	}
>  
>  	drm_for_each_encoder(encoder, dev) {
>  		validate_encoder_possible_clones(encoder);
> diff --git a/include/drm/drm_encoder.h b/include/drm/drm_encoder.h
> index b236269f41ac..bd033c5618bf 100644
> --- a/include/drm/drm_encoder.h
> +++ b/include/drm/drm_encoder.h
> @@ -142,6 +142,10 @@ struct drm_encoder {
>  	 * the bits for all &drm_crtc objects this encoder can be connected to
>  	 * before calling drm_dev_register().
>  	 *
> +	 * As an exception to the above rule if any crtc can be connected to
> +	 * the encoder the driver can leave @possible_crtcs set to 0. The core
> +	 * will automagically fix this up by setting the bit for every crtc.
> +	 *
>  	 * You will get a WARN if you get this wrong in the driver.
>  	 *
>  	 * Note that since CRTC objects can't be hotplugged the assigned indices
> -- 
> 2.24.1
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch