[PATCH 01/22] drm: Add drm_mode_init()

[Ville Syrjala]

From: Ville Syrjälä <ville.syrjala at linux.intel.com>

Add a variant of drm_mode_copy() that explicitly clears out
the list head of the destination mode. Helpful to guarantee
we don't have stack garbage left in there for on-stack modes.

Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
---
 drivers/gpu/drm/drm_modes.c | 17 +++++++++++++++++
 include/drm/drm_modes.h     |  2 ++
 2 files changed, 19 insertions(+)

diff --git a/drivers/gpu/drm/drm_modes.c b/drivers/gpu/drm/drm_modes.c
index 96b13e36293c..40d4ce4a1da4 100644
--- a/drivers/gpu/drm/drm_modes.c
+++ b/drivers/gpu/drm/drm_modes.c
@@ -892,6 +892,23 @@ void drm_mode_copy(struct drm_display_mode *dst, const struct drm_display_mode *
 }
 EXPORT_SYMBOL(drm_mode_copy);
 
+/**
+ * drm_mode_init - initialize the mode from another mode
+ * @dst: mode to overwrite
+ * @src: mode to copy
+ *
+ * Copy an existing mode into another mode, zeroing the
+ * list head of the destination mode. Typically used
+ * to guarantee the list head is not left with stack
+ * garbage in on-stack modes.
+ */
+void drm_mode_init(struct drm_display_mode *dst, const struct drm_display_mode *src)
+{
+	memset(dst, 0, sizeof(*dst));
+	drm_mode_copy(dst, src);
+}
+EXPORT_SYMBOL(drm_mode_init);
+
 /**
  * drm_mode_duplicate - allocate and duplicate an existing mode
  * @dev: drm_device to allocate the duplicated mode for
diff --git a/include/drm/drm_modes.h b/include/drm/drm_modes.h
index 29ba4adf0c53..e6e5a588fab1 100644
--- a/include/drm/drm_modes.h
+++ b/include/drm/drm_modes.h
@@ -484,6 +484,8 @@ void drm_mode_set_crtcinfo(struct drm_display_mode *p,
 			   int adjust_flags);
 void drm_mode_copy(struct drm_display_mode *dst,
 		   const struct drm_display_mode *src);
+void drm_mode_init(struct drm_display_mode *dst,
+		   const struct drm_display_mode *src);
 struct drm_display_mode *drm_mode_duplicate(struct drm_device *dev,
 					    const struct drm_display_mode *mode);
 bool drm_mode_match(const struct drm_display_mode *mode1,
-- 
2.34.1