[PATCH v6 1/3] drm: Add helper to compare edids.

[Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>]

Many drivers would benefit from using
drm helper to compare edid, rather
than bothering with own implementation.

v2: Added documentation for this function.

Signed-off-by: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>
---
 drivers/gpu/drm/drm_edid.c | 33 +++++++++++++++++++++++++++++++++
 include/drm/drm_edid.h     |  9 +++++++++
 2 files changed, 42 insertions(+)

diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
index 82a4ceed3fcf..0639db9fd23f 100644
--- a/drivers/gpu/drm/drm_edid.c
+++ b/drivers/gpu/drm/drm_edid.c
@@ -1362,6 +1362,39 @@ static bool drm_edid_is_zero(const u8 *in_edid, int length)
 	return true;
 }
 
+/**
+ * drm_edid_are_equal - compare two edid blobs.
+ * @edid1: pointer to first blob
+ * @edid2: pointer to second blob
+ * This helper can be used during probing to determine if
+ * edid had changed.
+ */
+bool drm_edid_are_equal(const struct edid *edid1, const struct edid *edid2)
+{
+	int edid1_len, edid2_len;
+	bool edid1_present = edid1 != NULL;
+	bool edid2_present = edid2 != NULL;
+
+	if (edid1_present != edid2_present)
+		return false;
+
+	if (edid1) {
+
+		edid1_len = EDID_LENGTH * (1 + edid1->extensions);
+		edid2_len = EDID_LENGTH * (1 + edid2->extensions);
+
+		if (edid1_len != edid2_len)
+			return false;
+
+		if (memcmp(edid1, edid2, edid1_len))
+			return false;
+	}
+
+	return true;
+}
+EXPORT_SYMBOL(drm_edid_are_equal);
+
+
 /**
  * drm_edid_block_valid - Sanity check the EDID block (base or extension)
  * @raw_edid: pointer to raw EDID block
diff --git a/include/drm/drm_edid.h b/include/drm/drm_edid.h
index b9719418c3d2..b0c68b2d79ed 100644
--- a/include/drm/drm_edid.h
+++ b/include/drm/drm_edid.h
@@ -354,6 +354,15 @@ drm_load_edid_firmware(struct drm_connector *connector)
 }
 #endif
 
+/**
+ * drm_edid_are_equal - compare two edid blobs.
+ * @edid1: pointer to first blob
+ * @edid2: pointer to second blob
+ * This helper can be used during probing to determine if
+ * edid had changed.
+ */
+bool drm_edid_are_equal(const struct edid *edid1, const struct edid *edid2);
+
 int
 drm_hdmi_avi_infoframe_from_display_mode(struct hdmi_avi_infoframe *frame,
 					 struct drm_connector *connector,
-- 
2.17.1

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