UPSTREAM: media: v4l2-fwnode: link_frequency is an optional property

v4l2_fwnode_endpoint_alloc_parse() is intended as a replacement for
v4l2_fwnode_endpoint_parse(). It parses the "link-frequency" property and
if the property isn't found, it returns an error. However,
"link-frequency" is an optional property and if it does not exist is not
an error. Instead, the number of link frequencies is simply zero in that
case.

Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Reviewed-by: Niklas Sderlund <niklas.soderlund+renesas@ragnatech.se>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
(cherry picked from commit 06f8152027765e55da3afc23d87c5fdaf9e7a686)
Signed-off-by: Marc Herbert <marc.herbert@intel.com>

BUG=b:64133998
TEST=media device topology shows subdevs registered successfully
TEST=no camera regression

Change-Id: I762fe01c77a6cac8f8ec415a2d68a6707e331159
Reviewed-on: https://chromium-review.googlesource.com/711075
Commit-Ready: Tomasz Figa <tfiga@chromium.org>
Tested-by: Hyungwoo Yang <hyungwoo.yang@intel.com>
Reviewed-by: Tomasz Figa <tfiga@chromium.org>
Signed-off-by: Jacob Chen <jacob2.chen@rock-chips.com>

Author: Sakari Ailus

drivers/media/v4l2-core/v4l2-fwnode.c

@@ -247,23 +247,23 @@ struct v4l2_fwnode_endpoint *v4l2_fwnode_endpoint_alloc_parse(
 
 	rval = fwnode_property_read_u64_array(fwnode, "link-frequencies",
 					      NULL, 0);
-	if (rval < 0)
-		goto out_err;
-
-	vep->link_frequencies =
-		kmalloc_array(rval, sizeof(*vep->link_frequencies), GFP_KERNEL);
-	if (!vep->link_frequencies) {
-		rval = -ENOMEM;
-		goto out_err;
-	}
+	if (rval > 0) {
+		vep->link_frequencies =
+			kmalloc_array(rval, sizeof(*vep->link_frequencies),
+				      GFP_KERNEL);
+		if (!vep->link_frequencies) {
+			rval = -ENOMEM;
+			goto out_err;
+		}
 
-	vep->nr_of_link_frequencies = rval;
+		vep->nr_of_link_frequencies = rval;
 
-	rval = fwnode_property_read_u64_array(fwnode, "link-frequencies",
-					      vep->link_frequencies,
-					      vep->nr_of_link_frequencies);
-	if (rval < 0)
-		goto out_err;
+		rval = fwnode_property_read_u64_array(
+			fwnode, "link-frequencies", vep->link_frequencies,
+			vep->nr_of_link_frequencies);
+		if (rval < 0)
+			goto out_err;
+	}
 
 	return vep;