Commit 47b5ac7daa46 ("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 <[email protected]> Reviewed-by: Luca Ceresoli <[email protected]> Signed-off-by: Maxime Ripard <[email protected]> --- drivers/gpu/drm/drm_atomic_state_helper.c | 5 +++-- drivers/gpu/drm/drm_bridge.c | 8 ++++++-- include/drm/drm_bridge.h | 19 ++++++++++++++++++- 3 files changed, 27 insertions(+), 5 deletions(-) diff --git a/drivers/gpu/drm/drm_atomic_state_helper.c b/drivers/gpu/drm/drm_atomic_state_helper.c index f0688f2d83fe..9dfb9b6ba392 100644 --- a/drivers/gpu/drm/drm_atomic_state_helper.c +++ b/drivers/gpu/drm/drm_atomic_state_helper.c @@ -892,12 +892,13 @@ EXPORT_SYMBOL(drm_atomic_helper_bridge_destroy_state); * @bridge: the bridge this state refers to * * @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) { __drm_atomic_helper_private_obj_create_state(&bridge->base, &state->base); diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c index 1daac8a7f4c9..776856e23592 100644 --- a/drivers/gpu/drm/drm_bridge.c +++ b/drivers/gpu/drm/drm_bridge.c @@ -540,11 +540,14 @@ static struct drm_private_state * 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); return &state->base; } @@ -555,11 +558,12 @@ static const struct drm_private_state_funcs drm_bridge_priv_state_funcs = { .atomic_destroy_state = drm_bridge_atomic_destroy_priv_state, }; 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); } /** * drm_bridge_attach - attach the bridge to an encoder's chain * diff --git a/include/drm/drm_bridge.h b/include/drm/drm_bridge.h index 00a95f927e34..70e574fbf034 100644 --- a/include/drm/drm_bridge.h +++ b/include/drm/drm_bridge.h @@ -528,10 +528,26 @@ struct drm_bridge_funcs { * A valid drm_bridge_state object in case of success, an ERR_PTR() * giving the reason of the failure otherwise. */ 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: * * Check if anything is attached to the bridge output. * @@ -1373,11 +1389,12 @@ drm_bridge_get_current_state(struct drm_bridge *bridge) /* * Only atomic bridges will have bridge->base initialized by * 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); if (!bridge->base.state) -- 2.54.0
