Re: [PATCH 1/6] drm/atomic-helper: document drm_atomic_helper_check() restrictions

[Simona Vetter <simona.vetter@ffwll.ch>]

On Sun, Dec 22, 2024 at 07:00:41AM +0200, Dmitry Baryshkov wrote:
> The drm_atomic_helper_check() calls drm_atomic_helper_check_modeset()
> insternally. Document that corresponding restrictions also apply to the
> drivers that call the former function (as it's easy to miss the
> documentation for the latter function).
> 
> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>

Reviewed-by: Simona Vetter <simona.vetter@ffwll.ch>

> ---
>  drivers/gpu/drm/drm_atomic_helper.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
> index 5186d2114a503701e228e382cc45180b0c578d0c..f26887c3fe8b194137200f9f2426653274c50fda 100644
> --- a/drivers/gpu/drm/drm_atomic_helper.c
> +++ b/drivers/gpu/drm/drm_atomic_helper.c
> @@ -1059,6 +1059,15 @@ EXPORT_SYMBOL(drm_atomic_helper_check_planes);
>   * For example enable/disable of a cursor plane which have fixed zpos value
>   * would trigger all other enabled planes to be forced to the state change.
>   *
> + * IMPORTANT:
> + *
> + * As this function calls drm_atomic_helper_check_modeset() internally, its
> + * restrictions also apply:
> + * Drivers which set &drm_crtc_state.mode_changed (e.g. in their
> + * &drm_plane_helper_funcs.atomic_check hooks if a plane update can't be done
> + * without a full modeset) _must_ call drm_atomic_helper_check_modeset()
> + * function again after that change.
> + *
>   * RETURNS:
>   * Zero for success or -errno
>   */
> 
> -- 
> 2.39.5
> 

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