Re: [PATCH 2/2] [media] exynos4-is: FIMC port parse should fail if there's no endpoint

[Javier Martinez Canillas]

Hello Sylwester,

On 03/11/2016 10:03 AM, Sylwester Nawrocki wrote:
> On 03/04/2016 09:20 PM, Javier Martinez Canillas wrote:
>> The fimc_md_parse_port_node() function return 0 if an endpoint node is
>> not found but according to Documentation/devicetree/bindings/graph.txt,
>> a port must always have at least one enpoint.
>>
>> So return an -EINVAL errno code to the caller instead, so it knows that
>> the port node parse failed due an invalid Device Tree description.
> 
> I don't think it is forbidden to have a port node in device tree
> containing no endpoint nodes. Empty port node means only that,
> for example, a subsystem has a port/bus for connecting external
> devices but nothing is actually connected to it.
> 
> In case of Exynos CSIS it might not be so useful to have an empty
> port node specified in some top level *.dtsi file and only
> the endpoints specified in a board specific dts file. Nevertheless,
> I wouldn't be saying in general a port node must always have some
> endpoint node defined.
> 

You are right, I asked Laurent and he confirms what you said that
it's possible to have ports with no endpoints. I still think the
DT binding docs could be more clear but that's a separate issue.

> I could apply this patch as it doesn't do any harm considering
> existing dts files in the kernel tree (arch/arm/boot/dts/
> exynos4412-trats2.dts), but the commit description would need to
> be changed.
> 

No worries, the current code is correct if endpoints are optional
and this patch is wrong so it should not be applied.
Best regards,
-- 
Javier Martinez Canillas
Open Source Group
Samsung Research America