linux-kernel - [PATCH RESEND v3 3/4] drm/mode_object: add drm_mode_object_read

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Message-Id: <20241216-drm-small-improvements-v3-3-78bbc95ac776@bootlin.com>
Date: Mon, 16 Dec 2024 17:40:50 +0100
From: Luca Ceresoli <luca.ceresoli@...tlin.com>
To: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, 
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>, 
 David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>
Cc: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>, 
 Jani Nikula <jani.nikula@...ux.intel.com>, 
 Thomas Petazzoni <thomas.petazzoni@...tlin.com>, 
 dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org, 
 Luca Ceresoli <luca.ceresoli@...tlin.com>, 
 Louis Chauvet <louis.chauvet@...tlin.com>
Subject: [PATCH RESEND v3 3/4] drm/mode_object: add
 drm_mode_object_read_refcount()

Add a wrapper to kref_read() just like the ones already in place for
kref_get() and kref_put(). This will be used for sanity checks on object
lifetime.

Signed-off-by: Luca Ceresoli <luca.ceresoli@...tlin.com>

---

Changed in v3:

 * use conventions for 'Returns' doc syntax
 * ditch DRM_DEBUG() and as a consequence rework and simplify the entire
   function
 * fix function name in kerneldoc
---
 drivers/gpu/drm/drm_mode_object.c | 17 +++++++++++++++++
 include/drm/drm_mode_object.h     |  1 +
 2 files changed, 18 insertions(+)

diff --git a/drivers/gpu/drm/drm_mode_object.c b/drivers/gpu/drm/drm_mode_object.c
index df4cc0e8e263d5887a799cf1a61d998234be7158..b9a16aceb926782eb033434eb6967ce9fd2e94f7 100644
--- a/drivers/gpu/drm/drm_mode_object.c
+++ b/drivers/gpu/drm/drm_mode_object.c
@@ -217,6 +217,23 @@ void drm_mode_object_get(struct drm_mode_object *obj)
 }
 EXPORT_SYMBOL(drm_mode_object_get);
 
+/**
+ * drm_mode_object_read_refcount - read the refcount for a mode object
+ * @obj: DRM mode object
+ *
+ * Returns:
+ * The current object refcount if it is a refcounted modeset object, or 0
+ * for any other object.
+ */
+unsigned int drm_mode_object_read_refcount(struct drm_mode_object *obj)
+{
+	if (obj->free_cb)
+		return kref_read(&obj->refcount);
+
+	return 0;
+}
+EXPORT_SYMBOL(drm_mode_object_read_refcount);
+
 /**
  * drm_object_attach_property - attach a property to a modeset object
  * @obj: drm modeset object
diff --git a/include/drm/drm_mode_object.h b/include/drm/drm_mode_object.h
index c68edbd126d04d51221f50aa2b4166475543b59f..3d2c739e703888bf4520c61594d480f128d50e56 100644
--- a/include/drm/drm_mode_object.h
+++ b/include/drm/drm_mode_object.h
@@ -123,6 +123,7 @@ struct drm_mode_object *drm_mode_object_find(struct drm_device *dev,
 					     uint32_t id, uint32_t type);
 void drm_mode_object_get(struct drm_mode_object *obj);
 void drm_mode_object_put(struct drm_mode_object *obj);
+unsigned int drm_mode_object_read_refcount(struct drm_mode_object *obj);
 
 int drm_object_property_set_value(struct drm_mode_object *obj,
 				  struct drm_property *property,

-- 
2.34.1