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drm/bridge: Add new atomic_create_state callback

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Commit 47b5ac7daa ("drm/atomic: Add new atomic_create_state callback
to drm_private_obj") introduced a new pattern for allocating drm object
states: atomic_create_state, a dedicated hook that allocates and
initializes a pristine state without any side effect.

The bridge atomic_reset callback is already fallible and in practice
only allocates and initializes state without touching hardware.
However, the reset name does not make this contract clear: callers
and implementers cannot tell from the name alone whether the hardware
will be affected or when the hook is safe to call.

Add an atomic_create_state callback to drm_bridge_funcs to make the
contract explicit: allocate a pristine state, initialize it, no side
effects. The core calls it when available, falling back to
atomic_reset otherwise.

Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Tested-by: Luca Ceresoli <luca.ceresoli@bootlin.com> # imx8mp + sn65dsi84 + bridge hotplug
Link: https://patch.msgid.link/20260619-drm-no-more-bridge-reset-v3-6-ff399263111b@kernel.org
Signed-off-by: Maxime Ripard <mripard@kernel.org>
This commit is contained in:
Maxime Ripard 2026-06-19 14:24:11 +02:00
parent 16710bcb96
commit 376542696c
No known key found for this signature in database
GPG Key ID: 275FCE19A23DBE76
3 changed files with 27 additions and 5 deletions
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5
drivers/gpu/drm/drm_atomic_state_helper.c
View File

@ -894,8 +894,9 @@ EXPORT_SYMBOL(drm_atomic_helper_bridge_destroy_state);
* @state is assumed to be zeroed.
*
* Initializes the bridge state to default values. This is meant to be called
* by the bridge &drm_bridge_funcs.atomic_reset hook for bridges that subclass
* the bridge state.
* by the bridge &drm_bridge_funcs.atomic_create_state or
* &drm_bridge_funcs.atomic_reset hook for bridges that subclass the bridge
* state.
*/
void __drm_atomic_helper_bridge_state_init(struct drm_bridge_state *state,
struct drm_bridge *bridge)

8
drivers/gpu/drm/drm_bridge.c
View File

@ -542,7 +542,10 @@ drm_bridge_atomic_create_priv_state(struct drm_private_obj *obj)
struct drm_bridge *bridge = drm_priv_to_bridge(obj);
struct drm_bridge_state *state;
state = bridge->funcs->atomic_reset(bridge);
if (bridge->funcs->atomic_create_state)
state = bridge->funcs->atomic_create_state(bridge);
else
state = bridge->funcs->atomic_reset(bridge);
if (IS_ERR(state))
return ERR_CAST(state);
@ -557,7 +560,8 @@ static const struct drm_private_state_funcs drm_bridge_priv_state_funcs = {
static bool drm_bridge_is_atomic(struct drm_bridge *bridge)
{
return bridge->funcs->atomic_reset != NULL;
return (bridge->funcs->atomic_create_state ||
bridge->funcs->atomic_reset);
}
/**

19
include/drm/drm_bridge.h
View File

@ -530,6 +530,22 @@ struct drm_bridge_funcs {
*/
struct drm_bridge_state *(*atomic_reset)(struct drm_bridge *bridge);
/**
* @atomic_create_state:
*
* Allocate a pristine, initialized, state for the bridge
* object and return it. This callback must have no side
* effects: in 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, bridge state instance or an error pointer
* on failure.
*/
struct drm_bridge_state *(*atomic_create_state)(struct drm_bridge *bridge);
/**
* @detect:
*
@ -1375,7 +1391,8 @@ drm_bridge_get_current_state(struct drm_bridge *bridge)
* drm_atomic_private_obj_init(), so we need to make sure we're
* working with one before we try to use the lock.
*/
if (!bridge->funcs || !bridge->funcs->atomic_reset)
if (!bridge->funcs ||
!(bridge->funcs->atomic_reset || bridge->funcs->atomic_create_state))
return NULL;
drm_modeset_lock_assert_held(&bridge->base.lock);