Re: [PATCH v3 1/7] drm: Include the encoder itself in possible_clones

[Daniel Vetter <daniel@ffwll.ch>]

On Tue, Feb 11, 2020 at 06:22:02PM +0200, Ville Syrjala wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> 
> The docs say possible_clones should always include the encoder itself.
> Since most drivers don't want to deal with the complexities of cloning
> let's allow them to set possible_clones=0 and instead we'll fix that
> up in the core.
> 
> We can't put this special case into drm_encoder_init() because drivers
> will have to fill up possible_clones after adding all the relevant
> encoders. Otherwise they wouldn't know the proper encoder indexes to
> use. So we'll just do it just before registering the device.
> 
> v2: Don't set the bit if possible_clones!=0 so that the
>     validation (coming soon) will WARN (Thomas)
>     Fix up the docs to allow possible_clones==0 (Daniel)
>     .late_register() is too late, introduce drm_mode_config_validate()
>     which gets called _before_ we register the char device (Daniel)

Looks solid.

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

> 
> Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
> Cc: Daniel Vetter <daniel@ffwll.ch>
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> ---
>  drivers/gpu/drm/drm_crtc_internal.h |  1 +
>  drivers/gpu/drm/drm_drv.c           |  3 +++
>  drivers/gpu/drm/drm_mode_config.c   | 19 +++++++++++++++++++
>  include/drm/drm_encoder.h           |  4 +++-
>  4 files changed, 26 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/drm_crtc_internal.h b/drivers/gpu/drm/drm_crtc_internal.h
> index 16f2413403aa..ace363b4f82b 100644
> --- a/drivers/gpu/drm/drm_crtc_internal.h
> +++ b/drivers/gpu/drm/drm_crtc_internal.h
> @@ -82,6 +82,7 @@ int drm_mode_setcrtc(struct drm_device *dev,
>  /* drm_mode_config.c */
>  int drm_modeset_register_all(struct drm_device *dev);
>  void drm_modeset_unregister_all(struct drm_device *dev);
> +void drm_mode_config_validate(struct drm_device *dev);
>  
>  /* drm_modes.c */
>  const char *drm_get_mode_status_name(enum drm_mode_status status);
> diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
> index 7b1a628d1f6e..65a0acb79323 100644
> --- a/drivers/gpu/drm/drm_drv.c
> +++ b/drivers/gpu/drm/drm_drv.c
> @@ -946,6 +946,9 @@ int drm_dev_register(struct drm_device *dev, unsigned long flags)
>  	struct drm_driver *driver = dev->driver;
>  	int ret;
>  
> +	if (!driver->load)
> +		drm_mode_config_validate(dev);
> +
>  	if (drm_dev_needs_global_mutex(dev))
>  		mutex_lock(&drm_global_mutex);
>  
> diff --git a/drivers/gpu/drm/drm_mode_config.c b/drivers/gpu/drm/drm_mode_config.c
> index 08e6eff6a179..75e357c7e84d 100644
> --- a/drivers/gpu/drm/drm_mode_config.c
> +++ b/drivers/gpu/drm/drm_mode_config.c
> @@ -532,3 +532,22 @@ void drm_mode_config_cleanup(struct drm_device *dev)
>  	drm_modeset_lock_fini(&dev->mode_config.connection_mutex);
>  }
>  EXPORT_SYMBOL(drm_mode_config_cleanup);
> +
> +/*
> + * For some reason we want the encoder itself included in
> + * possible_clones. Make life easy for drivers by allowing them
> + * to leave possible_clones unset if no cloning is possible.
> + */
> +static void fixup_encoder_possible_clones(struct drm_encoder *encoder)
> +{
> +	if (encoder->possible_clones == 0)
> +		encoder->possible_clones = drm_encoder_mask(encoder);
> +}
> +
> +void drm_mode_config_validate(struct drm_device *dev)
> +{
> +	struct drm_encoder *encoder;
> +
> +	drm_for_each_encoder(encoder, dev)
> +		fixup_encoder_possible_clones(encoder);
> +}
> diff --git a/include/drm/drm_encoder.h b/include/drm/drm_encoder.h
> index 5623994b6e9e..22d6cdf729f1 100644
> --- a/include/drm/drm_encoder.h
> +++ b/include/drm/drm_encoder.h
> @@ -159,7 +159,9 @@ struct drm_encoder {
>  	 * encoders can be used in a cloned configuration, they both should have
>  	 * each another bits set.
>  	 *
> -	 * In reality almost every driver gets this wrong.
> +	 * As an exception to the above rule if the driver doesn't implement
> +	 * any cloning it can leave @possible_clones set to 0. The core will
> +	 * automagically fix this up by setting the bit for the encoder itself.
>  	 *
>  	 * Note that since encoder objects can't be hotplugged the assigned indices
>  	 * are stable and hence known before registering all objects.
> -- 
> 2.24.1
> 

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