Re: [PATCH] drm/simpledrm: Drop superfluous primary plane .atomic_check return logic

[Thomas Zimmermann]

Hi Javier

Am 31.08.22 um 13:12 schrieb Javier Martinez Canillas:

The simpledrm_primary_plane_helper_atomic_check() function is more complex
than needed. It first checks drm_atomic_helper_check_plane_state() returns
value to decide whether to return this or zero.

But it could just return that function return value directly. It also does
a check if new_plane_state->visible isn't set, but returns zero regardless.

Signed-off-by: Javier Martinez Canillas <javi...@redhat.com>
---

  drivers/gpu/drm/tiny/simpledrm.c | 15 ++++-----------
  1 file changed, 4 insertions(+), 11 deletions(-)

diff --git a/drivers/gpu/drm/tiny/simpledrm.c b/drivers/gpu/drm/tiny/simpledrm.c
index a81f91814595..0be47f40247a 100644
--- a/drivers/gpu/drm/tiny/simpledrm.c
+++ b/drivers/gpu/drm/tiny/simpledrm.c
@@ -485,21 +485,14 @@ static int 
simpledrm_primary_plane_helper_atomic_check(struct drm_plane *plane,
        struct drm_plane_state *new_plane_state = 
drm_atomic_get_new_plane_state(new_state, plane);
        struct drm_crtc *new_crtc = new_plane_state->crtc;
        struct drm_crtc_state *new_crtc_state = NULL;
-       int ret;

                new_crtc_state = drm_atomic_get_new_crtc_state(new_state, 
new_crtc);

-                                                 DRM_PLANE_NO_SCALING,
-                                                 DRM_PLANE_NO_SCALING,
-                                                 false, false);
-       if (ret)
-               return ret;
-       else if (!new_plane_state->visible)
-               return 0;
-
-       return 0;
+       return drm_atomic_helper_check_plane_state(new_plane_state, 
new_crtc_state,
+                                                  DRM_PLANE_NO_SCALING,
+                                                  DRM_PLANE_NO_SCALING,
+                                                  false, false);

if (new_crtc) - ret = drm_atomic_helper_check_plane_state(new_plane_state, new_crtc_state,

Best regards
Thomas

I'm undecided on this change. I know it's correct and more to the point. But the call's logic is non-intuitive: the call either returns an error or we have to test ->visible afterwards. So I wrote it explicitly. I saw that your change to ssd130x also uses the pattern. If we find more such drivers, we could implement the atomic check as a helper. I suggest drm_plane_helper_atomic_check_fixed() in drm_plane_helper.c

  }

static void simpledrm_primary_plane_helper_atomic_update(struct drm_plane *plane,

--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Ivo Totev

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