drm/drv: Add drmm managed registration helper for dmem cgroups.

Drivers will need to register dmem regions at probe time, so let's
give them a drm-managed helper.

Signed-off-by: Maarten Lankhorst <dev@lankhorst.se>
Acked-by: Tejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20241204134410.1161769-3-dev@lankhorst.se
Signed-off-by: Maxime Ripard <mripard@kernel.org>

Author: mripard

drivers/gpu/drm/drm_drv.c

@@ -26,6 +26,7 @@
  * DEALINGS IN THE SOFTWARE.
  */
 
+#include <linux/cgroup_dmem.h>
 #include <linux/debugfs.h>
 #include <linux/fs.h>
 #include <linux/module.h>
@@ -820,6 +821,37 @@ void drm_dev_put(struct drm_device *dev)
 }
 EXPORT_SYMBOL(drm_dev_put);
 
+static void drmm_cg_unregister_region(struct drm_device *dev, void *arg)
+{
+	dmem_cgroup_unregister_region(arg);
+}
+
+/**
+ * drmm_cgroup_register_region - Register a region of a DRM device to cgroups
+ * @dev: device for region
+ * @region_name: Region name for registering
+ * @size: Size of region in bytes
+ *
+ * This decreases the ref-count of @dev by one. The device is destroyed if the
+ * ref-count drops to zero.
+ */
+struct dmem_cgroup_region *drmm_cgroup_register_region(struct drm_device *dev, const char *region_name, u64 size)
+{
+	struct dmem_cgroup_region *region;
+	int ret;
+
+	region = dmem_cgroup_register_region(size, "drm/%s/%s", dev->unique, region_name);
+	if (IS_ERR_OR_NULL(region))
+		return region;
+
+	ret = drmm_add_action_or_reset(dev, drmm_cg_unregister_region, region);
+	if (ret)
+		return ERR_PTR(ret);
+
+	return region;
+}
+EXPORT_SYMBOL_GPL(drmm_cgroup_register_region);
+
 static int create_compat_control_link(struct drm_device *dev)
 {
 	struct drm_minor *minor;

include/drm/drm_drv.h

@@ -34,6 +34,7 @@
 
 #include <drm/drm_device.h>
 
+struct dmem_cgroup_region;
 struct drm_fb_helper;
 struct drm_fb_helper_surface_size;
 struct drm_file;
@@ -438,6 +439,10 @@ void *__devm_drm_dev_alloc(struct device *parent,
 			   const struct drm_driver *driver,
 			   size_t size, size_t offset);
 
+struct dmem_cgroup_region *
+drmm_cgroup_register_region(struct drm_device *dev,
+			    const char *region_name, u64 size);
+
 /**
  * devm_drm_dev_alloc - Resource managed allocation of a &drm_device instance
  * @parent: Parent device object