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

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Date:   Wed, 10 May 2017 12:35:42 +0200
From:   Matthias Brugger <matthias.bgg@...il.com>
To:     Wolfram Sang <wsa@...-dreams.de>, Jun Gao <jun.gao@...iatek.com>
Cc:     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 28/03/17 21:22, Wolfram Sang wrote:
> 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.
> 

We will need to define the fallback binding for each SoC.
As example take the rockchip mmc:
http://elixir.free-electrons.com/linux/latest/source/Documentation/devicetree/bindings/mmc/rockchip-dw-mshc.txt

Regards,
Matthias

>>
>>>> ---
>>>>   .../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
>>>>
>>
>>