drm/prime: Add drm_gem_prime_mmap()

Add a generic PRIME GEM mmap function.

v2: Fix link in docs (Daniel Vetter)
Suggested-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Acked-by: Christian König <christian.koenig@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20181110145647.17580-3-noralf@tronnes.org

drivers/gpu/drm/drm_prime.c

@@ -651,6 +651,43 @@ int drm_gem_prime_handle_to_fd(struct drm_device *dev,
 }
 EXPORT_SYMBOL(drm_gem_prime_handle_to_fd);
 
+/**
+ * drm_gem_prime_mmap - PRIME mmap function for GEM drivers
+ * @obj: GEM object
+ * @vma: Virtual address range
+ *
+ * This function sets up a userspace mapping for PRIME exported buffers using
+ * the same codepath that is used for regular GEM buffer mapping on the DRM fd.
+ * The fake GEM offset is added to vma->vm_pgoff and &drm_driver->fops->mmap is
+ * called to set up the mapping.
+ *
+ * Drivers can use this as their &drm_driver.gem_prime_mmap callback.
+ */
+int drm_gem_prime_mmap(struct drm_gem_object *obj, struct vm_area_struct *vma)
+{
+	/* Used by drm_gem_mmap() to lookup the GEM object */
+	struct drm_file priv = {
+		.minor = obj->dev->primary,
+	};
+	struct file fil = {
+		.private_data = &priv,
+	};
+	int ret;
+
+	ret = drm_vma_node_allow(&obj->vma_node, &priv);
+	if (ret)
+		return ret;
+
+	vma->vm_pgoff += drm_vma_node_start(&obj->vma_node);
+
+	ret = obj->dev->driver->fops->mmap(&fil, vma);
+
+	drm_vma_node_revoke(&obj->vma_node, &priv);
+
+	return ret;
+}
+EXPORT_SYMBOL(drm_gem_prime_mmap);
+
 /**
  * drm_gem_prime_import_dev - core implementation of the import callback
  * @dev: drm_device to import into

include/drm/drm_prime.h

@@ -70,6 +70,7 @@ struct dma_buf *drm_gem_prime_export(struct drm_device *dev,
 int drm_gem_prime_handle_to_fd(struct drm_device *dev,
 			       struct drm_file *file_priv, uint32_t handle, uint32_t flags,
 			       int *prime_fd);
+int drm_gem_prime_mmap(struct drm_gem_object *obj, struct vm_area_struct *vma);
 struct drm_gem_object *drm_gem_prime_import(struct drm_device *dev,
 					    struct dma_buf *dma_buf);