[PATCH v3 10/20] drm/plane: Add new atomic_create_state callback

[Maxime Ripard]

Hi,

On Mon, May 04, 2026 at 07:52:29PM +0300, Laurent Pinchart wrote:
> On Fri, Apr 24, 2026 at 12:18:50PM +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 planes.
> > 
> > Signed-off-by: Maxime Ripard <mripard at kernel.org>
> > ---
> >  drivers/gpu/drm/drm_atomic_state_helper.c | 25 +++++++++++++++++++++++++
> >  drivers/gpu/drm/drm_mode_config.c         | 21 ++++++++++++++++++++-
> >  include/drm/drm_atomic_state_helper.h     |  2 ++
> >  include/drm/drm_plane.h                   | 16 ++++++++++++++++
> >  4 files changed, 63 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/gpu/drm/drm_atomic_state_helper.c b/drivers/gpu/drm/drm_atomic_state_helper.c
> > index 285efbf29520..50fe4eec41a8 100644
> > --- a/drivers/gpu/drm/drm_atomic_state_helper.c
> > +++ b/drivers/gpu/drm/drm_atomic_state_helper.c
> > @@ -338,10 +338,35 @@ void drm_atomic_helper_plane_reset(struct drm_plane *plane)
> >  	if (plane->state)
> >  		__drm_atomic_helper_plane_reset(plane, plane->state);
> >  }
> >  EXPORT_SYMBOL(drm_atomic_helper_plane_reset);
> >  
> > +/**
> > + * drm_atomic_helper_plane_create_state - default &drm_plane_funcs.atomic_create_state hook for planes
> 
> drm_atomic_helper_colorop_create_state() states "Allocates and
> initializes colorop atomic state", while here you document it as
> "default hook for planes". Consistency would be good.

I don't think it's inconsistent?

colorops don't have a create_state callback, so the only function to
create it is defined as "Allocates and initializes colorop atomic
state". For planes, the hook is documented as "Allocates a pristine,
initialized, state for the plane object and returns it.", and here we
have the default implementation for that hook, which is documented as
such.

It all seems consistent to me?

Maxime
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