Re: [PATCH 3/4] dt-bindings: mt8173-mtu3: add generic compatible and rename file

[Matthias Brugger]

On 08/11/2017 09:00 AM, Chunfeng Yun wrote:
> On Thu, 2017-08-10 at 21:54 -0500, Rob Herring wrote:
> > On Tue, Aug 08, 2017 at 01:42:51PM +0800, Chunfeng Yun wrote:
> > > The mt8173-mtu3.txt actually holds the bindings for all mediatek
> > > SoCs with usb3 DRD IP, so add a generic compatible and change the
> > > name to mtu3.txt.
> > >
> > > Signed-off-by: Chunfeng Yun <chunfeng.yun@xxxxxxxxxxxx>
> > > ---
> > >   .../bindings/usb/{mt8173-mtu3.txt => mtu3.txt}     |    6 ++++--
> > >   1 file changed, 4 insertions(+), 2 deletions(-)
> > >   rename Documentation/devicetree/bindings/usb/{mt8173-mtu3.txt => mtu3.txt} (95%)
> > >
> > > diff --git a/Documentation/devicetree/bindings/usb/mt8173-mtu3.txt b/Documentation/devicetree/bindings/usb/mtu3.txt
> > > similarity index 95%
> > > rename from Documentation/devicetree/bindings/usb/mt8173-mtu3.txt
> > > rename to Documentation/devicetree/bindings/usb/mtu3.txt
> > > index 1d7c3bc..832741d 100644
> > > --- a/Documentation/devicetree/bindings/usb/mt8173-mtu3.txt
> > > +++ b/Documentation/devicetree/bindings/usb/mtu3.txt
> >
> > mediatek,mtu3.txt
> Ok
> > > @@ -1,7 +1,9 @@
> > >   The device node for Mediatek USB3.0 DRD controller
> > >   
> > >   Required properties:
> > > - - compatible : should be "mediatek,mt8173-mtu3"
> > > + - compatible : should be one of
> > > +	"mediatek,mt8173-mtu3" (deprecated, use "mediatek,mtu3" instead),
> >
> > NAK. You can add generic compatibles, but you need SoC specific ones in
> > addition.
> It's for backward compatibility

I think backwards compatibility should be in the driver but not in the binding 
description. Apart from that device tree files will need to provide a SoC 
specific binding apart from the generic one, for example:

"mediatek,mt8173-mtu3", "mediatek,mtu3": for mt8173
"mediatek,mt7623-mtu3", "mediatek,mtu3": for mt6723

This is needed to cover possible bugs/features that can be found in the future 
for a specific SoC. The driver can match just against the generic binding and 
will only implement a match against the SoC specific one if a bug/feature is 
present.

Makes sense?

Regards,
Matthias