[RFC PATCH 2/3] media: qcom: camss: allow endpoints with no remote

[Richard Acayan <mailingradian@gmail.com>]

The camera subsystem is part of the Qualcomm platform, and common to
devices of the same platform (minus the devices that may omit it for
some reason). Different devices of the same SoC connect the camss to a
camera sensor with OF port and endpoint nodes. In the devicetree, the
SoC dtsi is responsible for defining the camera subsystem and ports,
while the device dts may connect some ports to a camera sensor and leave
others disconnected.

Currently, the camera subsystem separates SoC dtsi and device dts by
defining the ports in SoC, then using the top-level &camss label in the
device DTS to connect the ports. This is the standard, although still
disliked because a typo can cause the device DTS to define the
connection to the sensor in a newly created, unused node, with no
compile errors.

Another option that functions (the camera is exposed to userspace, even
though the approach is disliked), is defining and labelling the ports in
SoC so the device DTS can use the &camss_portX label to add an endpoint
and connect. This is disliked because an endpoint node is also labelled
in device DTS, so it adds clutter to the labelling.

The option used in SDM670 is to label an endpoint node, but also to
disable it. The device DTS can enable it to connect. This does not work
anymore.

When Vladimir clarified that the SDM670 camera subsystem isn't like DSI
because of the disabling, that gave a possible path forward. The option
used in DSI is to label an endpoint node in SoC and not to disable it,
but to leave it completely blank. Any endpoints that have no remote
endpoint (i.e. endpoints that are disconnected) are skipped. Skip the
endpoints with no remote node to allow an empty endpoint to be
pre-defined.

Cc: Vladimir Zapolskiy <vladimir.zapolskiy@linaro.org>
Cc: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
Cc: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Link: https://lore.kernel.org/r/e9dc1a6f-156b-40aa-9209-2010464d54ed@linaro.org
Link: https://lore.kernel.org/r/488281f6-5e5d-4864-8220-63e2a0b2d7f2@linaro.org
Link: https://lore.kernel.org/r/95704b74-52e7-4831-bc93-d4d7aa32736f@oss.qualcomm.com
Link: https://lore.kernel.org/r/79e2bb5b-9bca-4712-87bb-e0371b36bf50@linaro.org
Signed-off-by: Richard Acayan <mailingradian@gmail.com>
---
 drivers/media/platform/qcom/camss/camss.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/media/platform/qcom/camss/camss.c b/drivers/media/platform/qcom/camss/camss.c
index fcc2b2c3cba0..e9f0926ae92a 100644
--- a/drivers/media/platform/qcom/camss/camss.c
+++ b/drivers/media/platform/qcom/camss/camss.c
@@ -4092,9 +4092,8 @@ static int camss_of_parse_ports(struct camss *camss)
 
 		remote = of_graph_get_remote_port_parent(node);
 		if (!remote) {
-			dev_err(dev, "Cannot get remote parent\n");
-			ret = -EINVAL;
-			goto err_cleanup;
+			dev_dbg(dev, "Skipping endpoint due to missing remote port\n");
+			continue;
 		}
 
 		csd = v4l2_async_nf_add_fwnode(&camss->notifier,
-- 
2.52.0