drm/exynos: Add a new function to get gem buffer size

This patch adds a new function to get gem buffer size. And this
funtion could be used for g2d driver or others can get gem buffer
size to check if the buffer is valid or not.
Signed-off-by: NInki Dae <inki.dae@samsung.com>
Signed-off-by: NKyungmin Park <inki.dae@samsung.com>

drivers/gpu/drm/exynos/exynos_drm_gem.c

@@ -164,6 +164,27 @@ void exynos_drm_gem_destroy(struct exynos_drm_gem_obj *exynos_gem_obj)
 	exynos_gem_obj = NULL;
 }
 
+unsigned long exynos_drm_gem_get_size(struct drm_device *dev,
+						unsigned int gem_handle,
+						struct drm_file *file_priv)
+{
+	struct exynos_drm_gem_obj *exynos_gem_obj;
+	struct drm_gem_object *obj;
+
+	obj = drm_gem_object_lookup(dev, file_priv, gem_handle);
+	if (!obj) {
+		DRM_ERROR("failed to lookup gem object.\n");
+		return 0;
+	}
+
+	exynos_gem_obj = to_exynos_gem_obj(obj);
+
+	drm_gem_object_unreference_unlocked(obj);
+
+	return exynos_gem_obj->buffer->size;
+}
+
+
 struct exynos_drm_gem_obj *exynos_drm_gem_init(struct drm_device *dev,
 						      unsigned long size)
 {

drivers/gpu/drm/exynos/exynos_drm_gem.h

@@ -130,6 +130,11 @@ int exynos_drm_gem_userptr_ioctl(struct drm_device *dev, void *data,
 int exynos_drm_gem_get_ioctl(struct drm_device *dev, void *data,
 				      struct drm_file *file_priv);
 
+/* get buffer size to gem handle. */
+unsigned long exynos_drm_gem_get_size(struct drm_device *dev,
+						unsigned int gem_handle,
+						struct drm_file *file_priv);
+
 /* initialize gem object. */
 int exynos_drm_gem_init_object(struct drm_gem_object *obj);