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

diff --git a/drivers/gpu/drm/exynos/exynos_drm_core.c b/drivers/gpu/drm/exynos/exynos_drm_core.c
index 4c9f972eaa0771c0b2d9c5ff0f5480da3dc1e93d..ba64d23b90a72242a8ed58eb6cd2d15438634162 100644 (file)
--- 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);
        }