linux-kernel - Re: [RESEND PATCH v3 1/2] dt-bindings: i2c: Add Mediatek MT2701 i2c binding

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Date:   Tue, 28 Mar 2017 21:22:58 +0200
From:   Wolfram Sang <wsa@...-dreams.de>
To:     Jun Gao <jun.gao@...iatek.com>
Cc:     Matthias Brugger <matthias.bgg@...il.com>, robh@...nel.org,
        srv_heupstream@...iatek.com, devicetree@...r.kernel.org,
        linux-i2c@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, linux-mediatek@...ts.infradead.org,
        yingjoe.chen@...iatek.com
Subject: Re: [RESEND PATCH v3 1/2] dt-bindings: i2c: Add Mediatek MT2701 i2c
 binding

On Tue, Mar 28, 2017 at 05:50:12PM +0800, Jun Gao wrote:
> On Wed, 2017-03-22 at 10:05 +0100, Wolfram Sang wrote:
> > On Thu, Mar 09, 2017 at 11:13:04AM +0800, Jun Gao wrote:
> > > From: Jun Gao <jun.gao@...iatek.com>
> > > 
> > > Add MT2701 i2c binding to i2c-mt6577.txt and there is no need to
> > > modify i2c driver.
> > > 
> > > Signed-off-by: Jun Gao <jun.gao@...iatek.com>
> > 
> > There is still the issue which Matthias Brugger pointed out on January,
> > 24th: you need to describe the fallback compatibles.
> > 
> 
> IMHO the value under compatible are just inputs which can be accepted.
> It's little strange to add fallback information in binding. Some other
> bindings do not describe so detailedly.
> Is it OK to make binding as minimum standard?
> If we describe it very detailedly, we will have to modify binding if
> there are some changes for mt2701.

My reading of the below is that I could simply use "mediatek,mt2701-i2c"
as compatible and things will work. But it won't, we don't have that in
the driver IIRC. So, we need a fallback for that to work.

> Rob, could you give some suggestions?  Thanks!

Would be welcome, yes. I lost track what the preferred solution is.

> 
> > > ---
> > >  .../devicetree/bindings/i2c/i2c-mt6577.txt         |   11 ++++++-----
> > >  1 file changed, 6 insertions(+), 5 deletions(-)
> > > 
> > > diff --git a/Documentation/devicetree/bindings/i2c/i2c-mt6577.txt b/Documentation/devicetree/bindings/i2c/i2c-mt6577.txt
> > > index 0ce6fa3..27dbbf9 100644
> > > --- a/Documentation/devicetree/bindings/i2c/i2c-mt6577.txt
> > > +++ b/Documentation/devicetree/bindings/i2c/i2c-mt6577.txt
> > > @@ -4,11 +4,12 @@ The Mediatek's I2C controller is used to interface with I2C devices.
> > >  
> > >  Required properties:
> > >    - compatible: value should be either of the following.
> > > -      (a) "mediatek,mt6577-i2c", for i2c compatible with mt6577 i2c.
> > > -      (b) "mediatek,mt6589-i2c", for i2c compatible with mt6589 i2c.
> > > -      (c) "mediatek,mt8127-i2c", for i2c compatible with mt8127 i2c.
> > > -      (d) "mediatek,mt8135-i2c", for i2c compatible with mt8135 i2c.
> > > -      (e) "mediatek,mt8173-i2c", for i2c compatible with mt8173 i2c.
> > > +	"mediatek,mt2701-i2c"
> > > +	"mediatek,mt6577-i2c"
> > > +	"mediatek,mt6589-i2c"
> > > +	"mediatek,mt8127-i2c"
> > > +	"mediatek,mt8135-i2c"
> > > +	"mediatek,mt8173-i2c"
> > >    - reg: physical base address of the controller and dma base, length of memory
> > >      mapped region.
> > >    - interrupts: interrupt number to the cpu.
> > > -- 
> > > 1.7.9.5
> > > 
> 
> 

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