[PATCH 1/2] dt-bindings: display: bridge: ldb: Implement simple NXP i.MX8M LDB bridge

[Krzysztof Kozlowski]

On 13/03/2022 18:09, Marek Vasut wrote:
> On 3/13/22 16:47, Krzysztof Kozlowski wrote:
> 
> Hi,
> 
> [...]
> 
>>> diff --git a/Documentation/devicetree/bindings/display/bridge/nxp,ldb.yaml b/Documentation/devicetree/bindings/display/bridge/nxp,ldb.yaml
>>> new file mode 100644
>>> index 0000000000000..a05dd05547836
>>> --- /dev/null
>>> +++ b/Documentation/devicetree/bindings/display/bridge/nxp,ldb.yaml
>>> @@ -0,0 +1,99 @@
>>> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
>>> +%YAML 1.2
>>> +---
>>> +$id: http://devicetree.org/schemas/display/bridge/nxp,ldb.yaml#
>>
>> In title, description and commit msg you point this is specific to
>> i.MX8M, so maybe reflect it in the file name as well.
> 
> That's how it is so far, however NXP does recycle their IPs quite a bit 
> so I don't want to encode the SoC type into the bindings file name. I do 
> expect them to re-use this bridge somewhere else sooner rather than later.
> 
> [...]
> 
> The rest is fixed.
> 
> [...]
> 
>>> +examples:
>>> +  - |
>>> +    #include <dt-bindings/clock/imx8mp-clock.h>
>>> +
>>> +    lvds-ldb {
>>
>> Generic node name, so "bridge" or "display-bridge"
>>
>>> +        #address-cells = <0>;
>>> +        #size-cells = <0>;
>>
>> Why do you need address and size cells? This will complain if you test
>> your bindings with proper compatible.
> 
> Because the subnodes of this bridge have no dimension, so address/size 
> cells = 0.
> 
> I don't understand the second part about "proper compatible", can you 
> elaborate ?

You have wrong compatible in example and in bindings, so you do not see
the error of address/size cells.

They are also not required in your example, since you do not have unit
address. Otherwise your lvds-ldb node would be wrong (see its
address/size cells).

If you supply address-cells you should see a W=1 warning:
#address-cells/#size-cells without "ranges" or child "reg" property

Best regards,
Krzysztof