drm/panel: Add new helpers for refcounted panel allocatons

Introduce reference counted allocations for panels to avoid
use-after-free. The patch adds the macro devm_drm_bridge_alloc()
to allocate a new refcounted panel. Followed the documentation for
drmm_encoder_alloc() and devm_drm_dev_alloc and other similar
implementations for this purpose.

Reviewed-by: Maxime Ripard <mripard@kernel.org>
Signed-off-by: Anusha Srivatsa <asrivats@redhat.com>
Link: https://lore.kernel.org/r/20250331-b4-panel-refcounting-v4-1-dad50c60c6c9@redhat.com
Signed-off-by: Maxime Ripard <mripard@kernel.org>

2 files changed, 47 insertions, 0 deletions

diff --git a/drivers/gpu/drm/drm_panel.c b/drivers/gpu/drm/drm_panel.c
index c627e42a7ce7..bdeab5710ee3 100644
--- a/drivers/gpu/drm/drm_panel.c
+++ b/drivers/gpu/drm/drm_panel.c
@@ -355,6 +355,31 @@ struct drm_panel *of_drm_find_panel(const struct device_node *np)
 }
 EXPORT_SYMBOL(of_drm_find_panel);
 
+void *__devm_drm_panel_alloc(struct device *dev, size_t size, size_t offset,
+			     const struct drm_panel_funcs *funcs,
+			     int connector_type)
+{
+	void *container;
+	struct drm_panel *panel;
+
+	if (!funcs) {
+		dev_warn(dev, "Missing funcs pointer\n");
+		return ERR_PTR(-EINVAL);
+	}
+
+	container = devm_kzalloc(dev, size, GFP_KERNEL);
+	if (!container)
+		return ERR_PTR(-ENOMEM);
+
+	panel = container + offset;
+	panel->funcs = funcs;
+
+	drm_panel_init(panel, dev, funcs, connector_type);
+
+	return container;
+}
+EXPORT_SYMBOL(__devm_drm_panel_alloc);
+
 /**
  * of_drm_get_panel_orientation - look up the orientation of the panel through
  * the "rotation" binding from a device tree node
diff --git a/include/drm/drm_panel.h b/include/drm/drm_panel.h
index a9c042c8dea1..415e85e8b76a 100644
--- a/include/drm/drm_panel.h
+++ b/include/drm/drm_panel.h
@@ -268,6 +268,28 @@ struct drm_panel {
 	bool enabled;
 };
 
+void *__devm_drm_panel_alloc(struct device *dev, size_t size, size_t offset,
+			     const struct drm_panel_funcs *funcs,
+			     int connector_type);
+
+/**
+ * devm_drm_panel_alloc - Allocate and initialize a refcounted panel.
+ *
+ * @dev: struct device of the panel device
+ * @type: the type of the struct which contains struct &drm_panel
+ * @member: the name of the &drm_panel within @type
+ * @funcs: callbacks for this panel
+ * @connector_type: the connector type (DRM_MODE_CONNECTOR_*) corresponding to
+ * the panel interface
+ *
+ * Returns:
+ * Pointer to container structure embedding the panel, ERR_PTR on failure.
+ */
+#define devm_drm_panel_alloc(dev, type, member, funcs, connector_type) \
+	((type *)__devm_drm_panel_alloc(dev, sizeof(type), \
+					offsetof(type, member), funcs, \
+					connector_type))
+
 void drm_panel_init(struct drm_panel *panel, struct device *dev,
 		    const struct drm_panel_funcs *funcs,
 		    int connector_type);