drm: cleanup drm_core_{init,exit}()

Various cleanups to the DRM core initialization and exit handlers:

 - Register chrdev last: Once register_chrdev() returns, open() will
   succeed on the given chrdevs. This is usually not an issue, as no
   chardevs are registered, yet. However, nodes can be created by
   user-space via mknod(2), even though such major/minor combinations are
   unknown to the kernel. Avoid calling into drm_stub_open() in those
   cases.
   Again, drm_stub_open() would just bail out as the inode is unknown,
   but it's really non-obvious if you hack on drm_stub_open().

 - Unify error-paths into just one label. All the error-path helpers can
   be called even though the constructors were not called yet, or failed.
   Hence, just call all cleanups unconditionally.

 - Call into drm_global_release(). This is a no-op, but provides
   debugging helpers in case there're GLOBALS left on module unload. This
   function was unused until now.

 - Use DRM_ERROR() instead of printk(), and also print the error-code on
   failure (even if it is static!).

 - Don't throw away error-codes of register_chrdev()!

 - Don't hardcode -1 as errno. This is just plain wrong.

 - Order exit-handlers in the exact reverse order of initialization
   (except if the order actually matters for syncing-reasons, which is
   not the case here, though).

v2:
 - Call drm_core_exit() directly from the init-error-handler. Requires to
   drop __exit annotation, though.

Signed-off-by: David Herrmann <dh.herrmann@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/20160901124837.680-7-dh.herrmann@gmail.com

diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
index bcd54d4..f2f6429 100644 (file)
--- a/drivers/gpu/drm/drm_drv.c
+++ b/drivers/gpu/drm/drm_drv.c
@@ -820,52 +820,48 @@ static const struct file_operations drm_stub_fops = {
        .llseek = noop_llseek,
 };
 
+static void drm_core_exit(void)
+{
+       unregister_chrdev(DRM_MAJOR, "drm");
+       debugfs_remove(drm_debugfs_root);
+       drm_sysfs_destroy();
+       idr_destroy(&drm_minors_idr);
+       drm_connector_ida_destroy();
+       drm_global_release();
+}
+
 static int __init drm_core_init(void)
 {
-       int ret = -ENOMEM;
+       int ret;
 
        drm_global_init();
        drm_connector_ida_init();
        idr_init(&drm_minors_idr);
 
-       if (register_chrdev(DRM_MAJOR, "drm", &drm_stub_fops))
-               goto err_p1;
-
        ret = drm_sysfs_init();
        if (ret < 0) {
-               printk(KERN_ERR "DRM: Error creating drm class.\n");
-               goto err_p2;
+               DRM_ERROR("Cannot create DRM class: %d\n", ret);
+               goto error;
        }
 
        drm_debugfs_root = debugfs_create_dir("dri", NULL);
        if (!drm_debugfs_root) {
-               DRM_ERROR("Cannot create /sys/kernel/debug/dri\n");
-               ret = -1;
-               goto err_p3;
+               ret = -ENOMEM;
+               DRM_ERROR("Cannot create debugfs-root: %d\n", ret);
+               goto error;
        }
 
+       ret = register_chrdev(DRM_MAJOR, "drm", &drm_stub_fops);
+       if (ret < 0)
+               goto error;
+
        DRM_INFO("Initialized\n");
        return 0;
-err_p3:
-       drm_sysfs_destroy();
-err_p2:
-       unregister_chrdev(DRM_MAJOR, "drm");
 
-       idr_destroy(&drm_minors_idr);
-err_p1:
+error:
+       drm_core_exit();
        return ret;
 }
 
-static void __exit drm_core_exit(void)
-{
-       debugfs_remove(drm_debugfs_root);
-       drm_sysfs_destroy();
-
-       unregister_chrdev(DRM_MAJOR, "drm");
-
-       drm_connector_ida_destroy();
-       idr_destroy(&drm_minors_idr);
-}
-
 module_init(drm_core_init);
 module_exit(drm_core_exit);