Re: [PATCH 02/14] drm/atomic: Drop drm_private_state.obj assignment from create_state

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

On Tue, Mar 10, 2026 at 05:06:54PM +0100, Maxime Ripard wrote:
> The initial intent of the atomic_create_state helper was to simply
> allocate a proper drm_private_state and returning it, without any side
> effect.
> 
> However, the __drm_atomic_helper_private_obj_create_state() introduces a
> side effect by setting the drm_private_obj.state to the newly allocated
> state.
> 
> This assignment defeats the purpose, but is also redundant since
> the only caller, drm_atomic_private_obj_init(), will also set this
> pointer to the newly allocated state.

__drm_atomic_helper_bridge_reset() is called in many places. Most of
them are .atomic_create_state() handlers, called from
drm_atomic_private_obj_init() only. The only exception is
__drm_atomic_helper_bridge_reset(). Are you sure this patch won't cause
any negative side effect there ? The commit message should explain why.

> 
> Let's drop the assignment in __drm_atomic_helper_private_obj_create_state().
> 
> Fixes: e7be39ed1716 ("drm/atomic-helper: Add private_obj atomic_create_state helper")
> Signed-off-by: Maxime Ripard <mripard@kernel.org>
> ---
>  drivers/gpu/drm/drm_atomic_state_helper.c | 2 --
>  1 file changed, 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_atomic_state_helper.c b/drivers/gpu/drm/drm_atomic_state_helper.c
> index bd6faa09f83b498b1417869493f31d876cd13914..323abc9926e084ad595768c06d5c5ee28c22c014 100644
> --- a/drivers/gpu/drm/drm_atomic_state_helper.c
> +++ b/drivers/gpu/drm/drm_atomic_state_helper.c
> @@ -728,12 +728,10 @@ EXPORT_SYMBOL(drm_atomic_helper_connector_destroy_state);
>  void __drm_atomic_helper_private_obj_create_state(struct drm_private_obj *obj,
>  						  struct drm_private_state *state)
>  {
>  	if (state)
>  		state->obj = obj;
> -
> -	obj->state = state;
>  }
>  EXPORT_SYMBOL(__drm_atomic_helper_private_obj_create_state);
>  
>  /**
>   * __drm_atomic_helper_private_obj_duplicate_state - copy atomic private state
> 

-- 
Regards,

Laurent Pinchart