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

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Message-ID: <5a249ae3-e3f7-8eff-4022-ed982e364326@ti.com>
Date:   Mon, 17 Sep 2018 10:24:21 -0500
From:   Dan Murphy <dmurphy@...com>
To:     Jacek Anaszewski <jacek.anaszewski@...il.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

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.

Dan

> 
> [0]
> https://git.kernel.org/pub/scm/linux/kernel/git/tmlind/linux-omap.git/commit/?h=droid4-pending-v4.19&id=d774c7e447ac911e73a1b3c775e6d89f0422218c
> 


-- 
------------------
Dan Murphy