linux-kernel - Re: [PATCH v7 1/6] dt-bindings: ti-lmu: Remove LM3697

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Date:   Mon, 17 Sep 2018 21:22:54 +0200
From:   Jacek Anaszewski <jacek.anaszewski@...il.com>
To:     Dan Murphy <dmurphy@...com>, Pavel Machek <pavel@....cz>
Cc:     robh+dt@...nel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, lee.jones@...aro.org,
        linux-omap@...r.kernel.org, linux-leds@...r.kernel.org
Subject: Re: [PATCH v7 1/6] dt-bindings: ti-lmu: Remove LM3697

Dan,

On 09/17/2018 05:24 PM, Dan Murphy wrote:
> Jacek
> 
> On 09/15/2018 03:00 PM, Jacek Anaszewski wrote:
>> Hi Pavel.
>>
>> On 09/14/2018 11:42 PM, Pavel Machek wrote:
>>> Hi!
>>>
>>>>> You may want to learn more about device tree and/or talk to the device
>>>>> tree maintainers. This is an old article. https://lwn.net/Articles/561462/
>>>>
>>>> The article title is "Device trees as ABI". A device tree is defined
>>>> in the "*.dts" file that is then compiled to a dtb blob, which
>>>> constitutes the ABI. And this ABI should be kept backwards compatible.
>>>>
>>>> What is discussed here is a documentation of bindings, i.e. according
>>>> to ePAPR: "requirements for how specific types and classes of devices
>>>> are represented in the device tree".
>>>>
>>>> >From the bindings documented in the
>>>> Documentation/devicetree/bindings/mfd/ti-lmu.txt only
>>>> ti,lm3532-backlight is used in the mainline dts file
>>>> (arch/arm/boot/dts/omap4-droid4-xt894.dts).
>>>>
>>>> Having the above it seems that there is no risk of breaking any
>>>> users.
>>>
>>> DTBs and bindings are supposed to be portable between operating
>>> systems. You are right there are no _mainline_ _Linux_ users.
>>
>> No mainline users means no users we should care of.
>> Other people also don't care - see patch [0].
>>
>>>>> NAK on this patch. I see that this binding has problems, but
>>>>> introducing different binding for subset of devices is _not_ a fix.
>>>>>
>>>>>>> What about the multi function devices? They should have same binding.
>>>>>>
>>>>>> The MFD devices defined are not in contention here only the SFD.
>>>>>
>>>>> I'd like to see common solutions for SFD and MFD, as the hardware is
>>>>> similar, and that includes the code. Having code that is easier to
>>>>> maintain is important, and having many drivers are harder to maintain
>>>>> than one driver.
>>>>>
>>>>> Milo's code looks better than yours in that regard. I disagree about
>>>>> Milo's code being "nightmare" to modify, and care about "easy to
>>>>> maintain" more than "binary size".
>>>>
>>>> Easy to maintain will be a dedicated LED class driver.
>>>
>>> You mean, 3 dedicated LED class drivers and 3 MFD drivers with LED
>>> parts? We'll need complex driver anyway, and I'd really like to have
>>> just one.
>>
>> In the LED subsystem we can wrap common functionalities
>> into a library object. MFD driver will be able to reuse it then.
> 
> I am currently working on that code now.  I expect a RFC on this this week.

Will it affect the shape of the driver for lm3697 as of v7 [0]?
Or the patch set [0] state should be deemed "awaiting merge"?

[0] https://lkml.org/lkml/2018/9/11/760

-- 
Best regards,
Jacek Anaszewski