Re: [PATCH v4 2/7] dt-bindings: ti-lmu: Modify dt bindings for the LM3697
From: Dan Murphy
Date: Thu Oct 25 2018 - 14:07:43 EST
On 10/24/2018 09:54 AM, Rob Herring wrote:
> On Wed, Oct 24, 2018 at 07:07:57AM -0500, Dan Murphy wrote:
>> On 10/24/2018 04:04 AM, Pavel Machek wrote:
>>>> The LM3697 is a single function LED driver. The single function LED
>>>> driver needs to reside in the LED directory as a dedicated LED driver
>>>> and not as a MFD device. The device does have common brightness and ramp
>>> So it is single function LED driver. That does not mean it can not
>>> share bindings with the rest. Where the bindings live is not imporant.
>> It can share bindings that are correctly done, not ones that are incomplete and incorrect.
>> Where bindings live is important to new Linux kernel developers and product
>> developers looking for the proper documentation on the H/W bindings.
>>>> reside in the Documentation/devicetree/bindings/leds directory and follow the
>>>> current LED and general bindings guidelines.
>>> What you forgot to tell us in the changelog:
>> I can add this to the changelog.
>>>> +Optional child properties:
>>>> + - runtime-ramp-up-msec: Current ramping from one brightness level to
>>>> + the a higher brightness level.
>>>> + Range from 2048 us - 117.44 s
>>> The other binding uses "ramp-up-msec". Tell us why you are changing this, or
>>> better don't change things needlessly.
>>> We don't want to be using "runtime-ramp-up-msec" for one device and
>>> "ramp-up-msec" for the other.
>> This is another example of how the original bindings were incorrect and misleading.
>> The LM3697 have 2 ramp implementations that can be used.
>> Startup/Shutdown ramp and Runtime Ramp. Same Ramp rates different registers and
>> different end user experience.
>> So having a single node call ramp-up-msec is misleading and it does not
>> indicate what the H/W will do.
> The existing ones aren't documented (present in the example is not
> documented). This seems like something that should be common rather than
> TI specific. Though it also seems more like something the user would
> want to control (i.e. sysfs) rather than fixed in DT.
Changing the runtime ramping or startup/shutdown ramping could also be done via sysfs.
I am not dedicated to having it in the DT file I was following prior art.
Do you have an opinion on this?