Re: [PATCH 1/2] leds: Add driver for Qualcomm LPG

From: Rob Herring <robh@kernel.org>
To: Pavel Machek <pavel@ucw.cz>
Cc: Bjorn Andersson <bjorn.andersson@linaro.org>,
	Richard Purdie <rpurdie@rpsys.net>,
	Jacek Anaszewski <jacek.anaszewski@gmail.com>,
	linux-kernel@vger.kernel.org, linux-leds@vger.kernel.org,
	linux-arm-msm@vger.kernel.org,
	Mark Rutland <mark.rutland@arm.com>,
	devicetree@vger.kernel.org
Subject: Re: [PATCH 1/2] leds: Add driver for Qualcomm LPG
Date: Tue, 28 Mar 2017 21:17:34 -0500	[thread overview]
Message-ID: <20170329021734.afhqmfpmbcjyv7bu@rob-hp-laptop> (raw)
In-Reply-To: <20170323203749.GB8563@amd>

On Thu, Mar 23, 2017 at 09:37:49PM +0100, Pavel Machek wrote:
> Hi!
> 
> > The Light Pulse Generator (LPG) is a PWM-block found in a wide range of
> > PMICs from Qualcomm. It can operate on fixed parameters or based on a
> > lookup-table, altering the duty cycle over time - which provides the
> > means for e.g. hardware assisted transitions of LED brightness.
> 
> Ok, this is not first hardware that supports something like this. We
> have similar hardware that can do blinking on Nokia N900 -- please
> take a look at leds-lp55*.c

And perhaps some alignment on the bindings too if the N900 has bindings.

> And it would be really good to provide hardware abstraction. We really
> don't want to have different userspace for LPG and for N900 and for

I'm interested in what this looks like as several AOSP platforms do 
tri-color LEDs with custom sysfs extensions.

Do any of the Dragonboards have tri-color LEDs?

Rob