Re: [rfc] leds: add TI LMU backlight driver

From: Pavel Machek
Date: Thu Aug 30 2018 - 16:18:31 EST


> > Here's preview of driver for TI LMU. It controls LEDs on Droid 4
> > smartphone, including keyboard and screen backlights.
> >
> > This adds backlight support for the following TI LMU
> > chips: LM3532, LM3631, LM3632, LM3633, LM3695 and LM3697.
> >
> > Signed-off-by: Milo Kim <>
> > [add LED subsystem support for keyboard backlight and rework DT
> > binding according to Rob Herrings feedback]
> > Signed-off-by: Sebastian Reichel <sebastian.reichel@xxxxxxxxxxxxxxx>
> > [remove backlight subsystem support for now]
> > Signed-off-by: Pavel Machek <pavel@xxxxxx>
> >
> > ---
> >
> > Does it looks mostly reasonable? I guess it will need some
> > s/BACKLIGHT/LEDS/ , and I'll need to remove my debugging hacks.
> >
> > I'd prefer this to be LED driver, first; I'll need to figure out what
> > to do with backlight. I guess something like existing "backlight"
> > trigger should do the trick.
> >
> I looked at this driver from Milo before submitting a specific LM3697 driver.

Aha. I did not realize that was for same hardware... I should have
cc-ed you, I guess.

> I do not like this driver.
> I don't like that it smashes numerous devices into some structure with varying register maps.

Can you elaborate? The chips are similar enough that single driver
makes sense, and we certainly want to maintain one driver, not 6
drivers differing only in .. what exactly?

> Not only that but it appears that you just pulled this driver from a repo and posted it without clean up.

a) No I did not, feel free to generate a diff.

b) Even if I did, why would that be a problem?

> If the devices share register maps and can be added to families I would prefer to do it that way.
> So if the LM3695 and LM3697 share the same features and register map they should be one driver
> The LM363x series may be able to be a different driver.

Well all 6 chips this driver supports seem to be similar enough, so
that single driver makes sense.

Best regards,
(cesky, pictures)

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