[PATCH 1/4] drm/plane: Make init functions panic consitently and explicitly

[Maxime Ripard]

All of the current plane init / allocation functions behave slightly
differently when it comes to argument sanitizing:

 - drm_universal_plane_init() implicitly panics if the drm_device
   pointer or the drm_plane_funcs pointer are NULL, and calls WARN_ON if
   there's no destroy implementation but goes on with the initialization.

 - drm_universal_plane_alloc() implicitly panics if the drm_device
   pointer is NULL, and will call WARN_ON and return an error if the
   drm_plane_funcs pointer is NULL.

 - drmm_universal_plane_alloc() implicitly panics if the drm_device
   pointer is NULL, and will call WARN_ON and return an error if the
   drm_plane_funcs pointer is NULL or if there is a destroy
   implementation.

The current consensus is that the drm_device pointer, the
drm_plane_funcs pointer, and the drm_plane pointer if relevant, should
be considered pre-requisite and the function should panic if we
encounter such a situation, and that returning an error in such a
situation is not welcome.

Let's make all functions consider those three pointers to be always set
and explicitly panic if they aren't. And let's document that behaviour
too.

Link: https://lore.kernel.org/dri-devel/20231128-kms-hdmi-connector-state-v4-5-c7602158306e@kernel.org/
Signed-off-by: Maxime Ripard <mripard at kernel.org>
---
 drivers/gpu/drm/drm_plane.c | 15 +++++++++++----
 include/drm/drm_plane.h     |  6 ++++++
 2 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/drm_plane.c b/drivers/gpu/drm/drm_plane.c
index 9e8e4c60983d..ce0fa98a0e3f 100644
--- a/drivers/gpu/drm/drm_plane.c
+++ b/drivers/gpu/drm/drm_plane.c
@@ -482,6 +482,9 @@ static int __drm_universal_plane_init(struct drm_device *dev,
  *
  * Returns:
  * Zero on success, error code on failure.
+ *
+ * Panics:
+ * If @dev, @plane or @funcs are NULL.
  */
 int drm_universal_plane_init(struct drm_device *dev, struct drm_plane *plane,
 			     uint32_t possible_crtcs,
@@ -494,6 +497,9 @@ int drm_universal_plane_init(struct drm_device *dev, struct drm_plane *plane,
 	va_list ap;
 	int ret;
 
+	BUG_ON(!dev);
+	BUG_ON(!plane);
+	BUG_ON(!funcs);
 	WARN_ON(!funcs->destroy);
 
 	va_start(ap, name);
@@ -528,8 +534,9 @@ void *__drmm_universal_plane_alloc(struct drm_device *dev, size_t size,
 	va_list ap;
 	int ret;
 
-	if (WARN_ON(!funcs || funcs->destroy))
-		return ERR_PTR(-EINVAL);
+	BUG_ON(!dev);
+	BUG_ON(!funcs);
+	WARN_ON(funcs->destroy);
 
 	container = drmm_kzalloc(dev, size, GFP_KERNEL);
 	if (!container)
@@ -567,8 +574,8 @@ void *__drm_universal_plane_alloc(struct drm_device *dev, size_t size,
 	va_list ap;
 	int ret;
 
-	if (drm_WARN_ON(dev, !funcs))
-		return ERR_PTR(-EINVAL);
+	BUG_ON(!dev);
+	BUG_ON(!funcs);
 
 	container = kzalloc(size, GFP_KERNEL);
 	if (!container)
diff --git a/include/drm/drm_plane.h b/include/drm/drm_plane.h
index c6565a6f9324..2dab1b360fa2 100644
--- a/include/drm/drm_plane.h
+++ b/include/drm/drm_plane.h
@@ -824,6 +824,9 @@ void *__drmm_universal_plane_alloc(struct drm_device *dev,
  *
  * Returns:
  * Pointer to new plane, or ERR_PTR on failure.
+ *
+ * Panics:
+ * If @dev or @funcs are NULL.
  */
 #define drmm_universal_plane_alloc(dev, type, member, possible_crtcs, funcs, formats, \
 				   format_count, format_modifiers, plane_type, name, ...) \
@@ -868,6 +871,9 @@ void *__drm_universal_plane_alloc(struct drm_device *dev,
  *
  * Returns:
  * Pointer to new plane, or ERR_PTR on failure.
+ *
+ * Panics:
+ * If @dev or @funcs are NULL.
  */
 #define drm_universal_plane_alloc(dev, type, member, possible_crtcs, funcs, formats, \
 				   format_count, format_modifiers, plane_type, name, ...) \
-- 
2.43.0