Re: [PATCH v3 15/20] drm/connector: Add new atomic_create_state callback

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

Hi Maxime,

Thank you for the patch.

On Fri, Apr 24, 2026 at 12:18:55PM +0200, Maxime Ripard wrote:
> Commit 47b5ac7daa46 ("drm/atomic: Add new atomic_create_state callback
> to drm_private_obj") introduced a new pattern for allocating drm object
> states.
> 
> Instead of relying on the reset() callback, it created a new
> atomic_create_state hook. This is helpful because reset is a bit
> overloaded: it's used to create the initial software state, reset it,
> but also reset the hardware.
> 
> It can also be used either at probe time, to create the initial state
> and possibly reset the hardware to an expected default, but also during
> suspend/resume.
> 
> Both these cases come with different expectations too: during the
> initialization, we want to initialize all states, but during
> suspend/resume, drm_private_states for example are expected to be kept
> around.
> 
> reset() also isn't fallible, which makes it harder to handle
> initialization errors properly. This is only really relevant for some
> drivers though, since all the helpers for reset only create a new
> state, and don't touch the hardware at all.
> 
> It was thus decided to create a new hook that would allocate and
> initialize a pristine state without any side effect:
> atomic_create_state to untangle a bit some of it, and to separate the
> initialization with the actual reset one might need during a
> suspend/resume.
> 
> Continue the transition to the new pattern with connectors.
> 
> Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
> Signed-off-by: Maxime Ripard <mripard@kernel.org>
> ---
>  drivers/gpu/drm/drm_atomic_state_helper.c | 26 ++++++++++++++++++++++++++
>  drivers/gpu/drm/drm_mode_config.c         | 21 ++++++++++++++++++++-
>  include/drm/drm_atomic_state_helper.h     |  2 ++
>  include/drm/drm_connector.h               | 16 ++++++++++++++++
>  4 files changed, 64 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/drm_atomic_state_helper.c b/drivers/gpu/drm/drm_atomic_state_helper.c
> index f67aacaa3b6e..6140926f4605 100644
> --- a/drivers/gpu/drm/drm_atomic_state_helper.c
> +++ b/drivers/gpu/drm/drm_atomic_state_helper.c
> @@ -554,10 +554,36 @@ void drm_atomic_helper_connector_reset(struct drm_connector *connector)
>  	kfree(connector->state);
>  	__drm_atomic_helper_connector_reset(connector, conn_state);
>  }
>  EXPORT_SYMBOL(drm_atomic_helper_connector_reset);
>  
> +/**
> + * drm_atomic_helper_connector_create_state - default &drm_connector_funcs.atomic_create_state hook for connectors

Same comment as in 10/20.

> + * @connector: connector object
> + *
> + * Initializes a pristine @drm_connector_state.

"Allocate and initialize ..."

> + *
> + * This is useful for drivers that don't subclass @drm_connector_state.
> + *
> + * RETURNS:
> + * Pointer to new connector state, or ERR_PTR on failure.
> + */
> +struct drm_connector_state *
> +drm_atomic_helper_connector_create_state(struct drm_connector *connector)
> +{
> +	struct drm_connector_state *state;
> +
> +	state = kzalloc_obj(*state);
> +	if (!state)
> +		return ERR_PTR(-ENOMEM);
> +
> +	__drm_atomic_helper_connector_state_init(state, connector);
> +
> +	return state;
> +}
> +EXPORT_SYMBOL(drm_atomic_helper_connector_create_state);
> +
>  /**
>   * drm_atomic_helper_connector_tv_margins_reset - Resets TV connector properties
>   * @connector: DRM connector
>   *
>   * Resets the TV-related properties attached to a connector.
> diff --git a/drivers/gpu/drm/drm_mode_config.c b/drivers/gpu/drm/drm_mode_config.c
> index 182d9a8104e7..92ff907f2485 100644
> --- a/drivers/gpu/drm/drm_mode_config.c
> +++ b/drivers/gpu/drm/drm_mode_config.c
> @@ -212,10 +212,26 @@ static int drm_mode_config_crtc_create_state(struct drm_crtc *crtc)
>  	crtc->state = crtc_state;
>  
>  	return 0;
>  }
>  
> +static int drm_mode_config_connector_create_state(struct drm_connector *connector)
> +{
> +	struct drm_connector_state *conn_state;
> +
> +	if (!connector->funcs->atomic_create_state)
> +		return 0;
> +
> +	conn_state = connector->funcs->atomic_create_state(connector);
> +	if (IS_ERR(conn_state))
> +		return PTR_ERR(conn_state);
> +
> +	connector->state = conn_state;
> +
> +	return 0;
> +}
> +
>  /**
>   * drm_mode_config_reset - call ->reset callbacks
>   * @dev: drm device
>   *
>   * This functions calls all the crtc's, encoder's and connector's ->reset
> @@ -255,13 +271,16 @@ void drm_mode_config_reset(struct drm_device *dev)
>  	drm_for_each_encoder(encoder, dev)
>  		if (encoder->funcs && encoder->funcs->reset)
>  			encoder->funcs->reset(encoder);
>  
>  	drm_connector_list_iter_begin(dev, &conn_iter);
> -	drm_for_each_connector_iter(connector, &conn_iter)
> +	drm_for_each_connector_iter(connector, &conn_iter) {
>  		if (connector->funcs->reset)
>  			connector->funcs->reset(connector);
> +		else if (connector->funcs->atomic_create_state)
> +			drm_mode_config_connector_create_state(connector);
> +	}
>  	drm_connector_list_iter_end(&conn_iter);
>  }
>  EXPORT_SYMBOL(drm_mode_config_reset);
>  
>  /*
> diff --git a/include/drm/drm_atomic_state_helper.h b/include/drm/drm_atomic_state_helper.h
> index e7c097e6dfe3..8576cd256737 100644
> --- a/include/drm/drm_atomic_state_helper.h
> +++ b/include/drm/drm_atomic_state_helper.h
> @@ -75,10 +75,12 @@ void drm_atomic_helper_plane_destroy_state(struct drm_plane *plane,
>  void __drm_atomic_helper_connector_state_init(struct drm_connector_state *conn_state,
>  					       struct drm_connector *connector);
>  void __drm_atomic_helper_connector_reset(struct drm_connector *connector,
>  					 struct drm_connector_state *conn_state);
>  void drm_atomic_helper_connector_reset(struct drm_connector *connector);
> +struct drm_connector_state *
> +drm_atomic_helper_connector_create_state(struct drm_connector *connector);
>  void drm_atomic_helper_connector_tv_reset(struct drm_connector *connector);
>  int drm_atomic_helper_connector_tv_check(struct drm_connector *connector,
>  					 struct drm_atomic_state *state);
>  void drm_atomic_helper_connector_tv_margins_reset(struct drm_connector *connector);
>  void
> diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
> index 3e422a4f2e72..9fb794957d23 100644
> --- a/include/drm/drm_connector.h
> +++ b/include/drm/drm_connector.h
> @@ -1569,10 +1569,26 @@ struct drm_connector_funcs {
>  	 * when a connector is being hot-unplugged for drivers that support
>  	 * connector hotplugging (e.g. DisplayPort MST).
>  	 */
>  	void (*destroy)(struct drm_connector *connector);
>  
> +	/**
> +	 * @atomic_create_state:
> +	 *
> +	 * Allocates a pristine, initialized, state for the connector object

s/Allocates/Allocate/

> +	 * and returns it. This callback must have no side effects: in

s/returns/return/

Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>

> +	 * particular, the returned state must not be assigned to the
> +	 * object's state pointer and it must not affect the hardware
> +	 * state.
> +	 *
> +	 * RETURNS:
> +	 *
> +	 * A new, pristine, connector state instance or an error pointer
> +	 * on failure.
> +	 */
> +	struct drm_connector_state *(*atomic_create_state)(struct drm_connector *connector);
> +
>  	/**
>  	 * @atomic_duplicate_state:
>  	 *
>  	 * Duplicate the current atomic state for this connector and return it.
>  	 * The core and helpers guarantee that any atomic state duplicated with

-- 
Regards,

Laurent Pinchart