linux-kernel - Re: [PATCH v3 2/7] mfd: retu: Add OF device ID table

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Message-ID: <0bb24412-3e3d-5ad9-ca87-6d1869c5e135@osg.samsung.com>
Date:   Mon, 3 Apr 2017 19:00:24 -0400
From:   Javier Martinez Canillas <javier@....samsung.com>
To:     Tony Lindgren <tony@...mide.com>,
        Aaro Koskinen <aaro.koskinen@....fi>
Cc:     Rob Herring <robh@...nel.org>, Lee Jones <lee.jones@...aro.org>,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
        Linux-OMAP <linux-omap@...r.kernel.org>
Subject: Re: [PATCH v3 2/7] mfd: retu: Add OF device ID table

Hello Aaro and Tony,

On 04/03/2017 06:58 PM, Tony Lindgren wrote:
> * Aaro Koskinen <aaro.koskinen@....fi> [170403 15:56]:
>> Hi,
>>
>> On Mon, Apr 03, 2017 at 06:24:39PM -0400, Javier Martinez Canillas wrote:
>>> On 04/03/2017 06:20 PM, Rob Herring wrote:
>>>> On Mon, Apr 03, 2017 at 11:45:14AM -0400, Javier Martinez Canillas wrote:
>>>>> Hello Lee,
>>>>>
>>>>> On 04/03/2017 07:15 AM, Lee Jones wrote:
>>>>>
>>>>> [snip]
>>>>>
>>>>>>>  
>>>>>>> +static const struct of_device_id retu_of_match[] = {
>>>>>>> +	{ .compatible = "nokia,retu-mfd" },
>>>>>>> +	{ .compatible = "nokia,tahvo-mfd" },
>>>>>>
>>>>>> Please drop the "-mfd".
>>>>>>
>>>>>
>>>>> Yes, I also didn't like it but I didn't want to change it since that would
>>>>> mean that backward compatiblity and bisect-ability will be broken by this
>>>>> change.
>>>>>
>>>>> In other words, just adding a vendor prefix won't cause an issue if patches
>>>>> are merged independently since if DTS patches are merged before, the driver
>>>>> will still lookup using the I2C device ID table. And if the drivers patches
>>>>> are picked before, the DTS will match using the OF device ID table.
>>>>>
>>>>> But changing to "nokia,retu" and "nokia,tahvo" means that you will need to
>>>>> pick all patches and also that the DTS and drivers changes will have to be
>>>>> done in the same patch. If you are OK with that, then I can change in the
>>>>> next version.
>>>>
>>>> tahvo is not documented nor used in any dts (in the kernel at least). 
>>
>> True, there are no known DT users of Tahvo.
>>
>>>> retu is used by 1 board and happened to work, but was never documented. 
>>>> So I think it is okay to change unless the N800 folks object.
>>>
>>> I'm fine with changing it (in fact I just want to fix the I2C of modalias
>>> reporting). Does this mean that backward compatibility and bisect-ability
>>> should be preserved? Or it's OK to split the changes in different patches?
>>
>> There are 2 boards actually, N800 and N810. Retu is critical, because
>> if retu-mfd/watchdog fails to probe the device will power off soon after
>> boot. So for bisect-ability you should make changes in a single patch.
>

Thanks for the confirmation. I'll squash the changes then in a single patch
to maintain bisect-ability.
 
> Also I wonder if this will work with arch/arm/mach-omap1/board-nokia770.c
> that does I2C_BOARD_INFO("tahvo-mfd", 0x02). Seems they all need to be
> changed with a single patch?
>

Yes, it has to be changed as well. So I guess that makes more sense if the
changes goes through your tree since is not only driver + DTS.
 
> Regards,
> 
> Tony
> 

Best regards,
-- 
Javier Martinez Canillas
Open Source Group
Samsung Research America