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SubjectRe: [PATCH v3 06/11] drm: Use state helper instead of plane state pointer in atomic_check
Hi Thomas,

On Mon, Feb 22, 2021 at 10:12:49AM +0100, Thomas Zimmermann wrote:
> Am 19.02.21 um 13:00 schrieb Maxime Ripard:
> > Many drivers reference the plane->state pointer in order to get the
> > current plane state in their atomic_check hook, which would be the old
> > plane state in the global atomic state since _swap_state hasn't happened
> > when atomic_check is run.
> >
> > Use the drm_atomic_get_old_plane_state helper to get that state to make
> > it more obvious.
> >
> > This was made using the coccinelle script below:
> >
> > @ plane_atomic_func @
> > identifier helpers;
> > identifier func;
> > @@
> >
> > static struct drm_plane_helper_funcs helpers = {
> > ...,
> > .atomic_check = func,
> > ...,
> > };
> >
> > @ replaces_old_state @
> > identifier plane_atomic_func.func;
> > identifier plane, state, plane_state;
> > @@
> >
> > func(struct drm_plane *plane, struct drm_atomic_state *state) {
> > ...
> > - struct drm_plane_state *plane_state = plane->state;
> > + struct drm_plane_state *plane_state = drm_atomic_get_old_plane_state(state, plane);
> > ...
> > }
> >
> > @@
> > identifier plane_atomic_func.func;
> > identifier plane, state, plane_state;
> > @@
> >
> > func(struct drm_plane *plane, struct drm_atomic_state *state) {
> > struct drm_plane_state *plane_state = drm_atomic_get_old_plane_state(state, plane);
> > <...
> > - plane->state
> > + plane_state
> > ...>
> > }
> >
> > @ adds_old_state @
> > identifier plane_atomic_func.func;
> > identifier plane, state;
> > @@
> >
> > func(struct drm_plane *plane, struct drm_atomic_state *state) {
> > + struct drm_plane_state *old_plane_state = drm_atomic_get_old_plane_state(state, plane);
> > <...
> > - plane->state
> > + old_plane_state
> > ...>
> > }
> >
> > @ include depends on adds_old_state || replaces_old_state @
> > @@
> >
> > #include <drm/drm_atomic.h>
> >
> > @ no_include depends on !include && (adds_old_state || replaces_old_state) @
> > @@
> >
> > + #include <drm/drm_atomic.h>
> > #include <drm/...>
> >
> > Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > Signed-off-by: Maxime Ripard <maxime@cerno.tech>
>
> Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
>
> However, I find 'old plane state' somewhat confusing in this context,
> because it's actually the current plane state. Would it make sense to use
> drm_atomic_get_existing_plane_state() instead?

drm_atomic_get_existing_plane_state is deprecated nowadays, in favour of either
drm_atomic_get_old_plane_state or drm_atomic_get_new_plane_state

Maxime
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