Re: [PATCH] DT: mmc: sh_mmcif: fix "compatible" property text

[Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>]

Hello.

On 7/31/2015 5:23 AM, Magnus Damm wrote:

>> The "compatible" property text contradicts even the example given in the MMCIF
>> binding document itself; moreover, the Renesas MMCIF driver only  matches  on
>> the generic "compatible" string, and doesn't look for at SoC specific strings
>> currently at all. Thus describe "renesas,sh-mmcif" string as mandatory and the
>> others as optional.

>> Fixes: b4c27763d749 ("mmc: sh_mmcif: Document DT bindings")
>> Signed-off-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>

> Thanks for your efforts trying to improve the DT binding documentation.

>> --- renesas.orig/Documentation/devicetree/bindings/mmc/renesas,mmcif.txt
>> +++ renesas/Documentation/devicetree/bindings/mmc/renesas,mmcif.txt
>> @@ -6,11 +6,11 @@ and the properties used by the MMCIF dev
>>
>>   Required properties:
>>
>> -- compatible: must contain one of the following
>> +- compatible: must contain "renesas,sh-mmcif"; may also contain one of
>> +  the following:
>>          - "renesas,mmcif-r8a7740" for the MMCIF found in r8a7740 SoCs
>>          - "renesas,mmcif-r8a7790" for the MMCIF found in r8a7790 SoCs
>>          - "renesas,mmcif-r8a7791" for the MMCIF found in r8a7791 SoCs
>> -       - "renesas,sh-mmcif" for the generic MMCIF

> As you know, each SoC contains a wide range of on-chip devices and the
> MMCIF device is just one of them. Exactly how to manage the DT
> bindings must be up to each maintainer and of course this needs to be
> aligned with the SoC maintainer and SoC vendor with policies used for
> SoC support and BSPs and whatnot. Changing policy like this for a
> single device without at least discussing this with the SoC
> maintainers does not help.

    I'm not changing the policy, I'm making the binding actually reflect the 
driver reality (and even the example given in the binding).

> For Renesas hardware we so far use both SoC part number and optionally
> a generic binding as well. As commonly expected, the DT binding is
> supposed to describe the hardware and if hardware devices are
> compatible. Unless we use SoC part number in the compatible string
> there is a risk that the SoC integrator simply copy-and-pastes generic
> bindings "because it works" but this will result in DT binding based
> on software compatibility and not hardware compatibility. Later when
> the driver support is extended this may result in broken software due
> to incorrect compatibility information through generic bindings.

> If anything is unclear please ask and feel free to discuss this DT
> topic with Simon, Laurent, Geert and/or me.

    I didn't quite understand what you're proposing instead. Making SoC based 
strings mandatory? Changing the driver to look at the SoC based strings?

> Thanks,

> / magnus

MBR, Sergei