drm/exynos: fix error handling in exynos_drm_subdrv_open

gcc-6 warns about a pointless loop in exynos_drm_subdrv_open:

drivers/gpu/drm/exynos/exynos_drm_core.c: In function 'exynos_drm_subdrv_open':
drivers/gpu/drm/exynos/exynos_drm_core.c:104:199: error: self-comparison always evaluates to false [-Werror=tautological-compare]
  list_for_each_entry_reverse(subdrv, &subdrv->list, list) {

Here, the list_for_each_entry_reverse immediately terminates because
the subdrv pointer is compared to itself as the loop end condition.

If we were to take the current subdrv pointer as the start of the
list (as we would do if list_for_each_entry_reverse() was not a macro),
we would iterate backwards over the &exynos_drm_subdrv_list anchor,
which would be even worse.

Instead, we need to use list_for_each_entry_continue_reverse()
to go back over each subdrv that was successfully opened until
the first entry.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Inki Dae <inki.dae@samsung.com>
[Backport from mainline to fix build warning with gcc6]
Signed-off-by: Seung-Woo Kim <sw0312.kim@samsung.com>

Change-Id: Iee4b9078f0bd521507716521a339b37ea5dd8776

1 files changed, 1 insertions, 1 deletions

diff --git a/drivers/gpu/drm/exynos/exynos_drm_core.c b/drivers/gpu/drm/exynos/exynos_drm_core.c
index 4c9f972eaa07..ba64d23b90a7 100644
--- a/drivers/gpu/drm/exynos/exynos_drm_core.c
+++ b/drivers/gpu/drm/exynos/exynos_drm_core.c
@@ -141,7 +141,7 @@ int exynos_drm_subdrv_open(struct drm_device *dev, struct drm_file *file)
 	return 0;
 
 err:
-	list_for_each_entry_reverse(subdrv, &subdrv->list, list) {
+	list_for_each_entry_continue_reverse(subdrv, &exynos_drm_subdrv_list, list) {
 		if (subdrv->close)
 			subdrv->close(dev, subdrv->dev, file);
 	}