Re: [PATCH v2 05/10] drm/simpledrm: Convert to atomic helpers

[Javier Martinez Canillas <javierm@redhat.com>]

On 7/20/22 16:27, Thomas Zimmermann wrote:
> Replace the simple-KMS helpers with the regular atomic helpers. The
> regular helpers are better architectured and therefore allow for easier
> code sharing among drivers. No functional changes.
>

Acked-by: Javier Martinez Canillas <javierm@redhat.com>

But I've a question below...
 
> Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
> ---
>  drivers/gpu/drm/tiny/simpledrm.c | 283 ++++++++++++++++++++-----------
>  1 file changed, 180 insertions(+), 103 deletions(-)

[...]

> +static void simpledrm_crtc_helper_atomic_enable(struct drm_crtc *crtc,
> +						struct drm_atomic_state *old_state)
> +{
> +	/*
> +	 * Always enabled; screen updates are performed by
> +	 * the primary plane's atomic_update function.
> +	 */
> +}
> +
> +static void simpledrm_crtc_helper_atomic_disable(struct drm_crtc *crtc,
> +						 struct drm_atomic_state *old_state)
> +{
> +	/*
> +	 * Always enabled; disabling clears the screen in the
> +	 * primary plane's atomic_disable function.
> +	 */
> +}

...do we really need to have these ? Can't we just not set them ?

> +
> +static const struct drm_crtc_helper_funcs simpledrm_crtc_helper_funcs = {
> +	.mode_valid = simpledrm_crtc_helper_mode_valid,
> +	.atomic_check = simpledrm_crtc_helper_atomic_check,
> +	.atomic_enable = simpledrm_crtc_helper_atomic_enable,
> +	.atomic_disable = simpledrm_crtc_helper_atomic_disable,
> +};
> +
looking at https://elixir.bootlin.com/linux/latest/source/include/drm/drm_modeset_helper_vtables.h#L703
that says the .atomic_{en,dis}able handlers are optional.

-- 
Best regards,

Javier Martinez Canillas
Linux Engineering
Red Hat