From: Marek Behun <marek.behun@nic.cz>
To: Hermes Zhang <Hermes.Zhang@axis.com>
Cc: Alexander Dahl <ada@thorsis.com>,
"linux-leds@vger.kernel.org" <linux-leds@vger.kernel.org>,
Pavel Machek <pavel@ucw.cz>, Dan Murphy <dmurphy@ti.com>,
kernel <kernel@axis.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] leds: leds-dual-gpio: Add dual GPIO LEDs driver
Date: Fri, 12 Mar 2021 10:03:27 +0100 [thread overview]
Message-ID: <20210312100327.3c3c47ba@nic.cz> (raw)
In-Reply-To: <e56946d1d85948c7b6ce94982a221981@XBOX03.axis.com>
On Fri, 12 Mar 2021 08:48:55 +0000
Hermes Zhang <Hermes.Zhang@axis.com> wrote:
> Hi Alexander,
>
> > Am Donnerstag, 11. März 2021, 14:04:08 CET schrieb Hermes Zhang:
> > > From: Hermes Zhang <chenhuiz@axis.com>
> > >
> > > Introduce a new Dual GPIO LED driver. These two GPIOs LED will act as
> > > one LED as normal GPIO LED but give the possibility to change the
> > > intensity in four levels: OFF, LOW, MIDDLE and HIGH.
> >
> > Interesting use case. Is there any real world hardware wired like that you
> > could point to?
> >
>
> Yes, we have the HW, it's not a chip but just some circuit to made of.
>
> > > +config LEDS_DUAL_GPIO
> > > + tristate "LED Support for Dual GPIO connected LEDs"
> > > + depends on LEDS_CLASS
> > > + depends on GPIOLIB || COMPILE_TEST
> > > + help
> > > + This option enables support for the two LEDs connected to GPIO
> > > + outputs. These two GPIO LEDs act as one LED in the sysfs and
> > > + perform different intensity by enable either one of them or both.
> >
> > Well, although I never had time to implement that, I suspect that could
> > conflict if someone will eventually write a driver for two pin dual color LEDs
> > connected to GPIO pins. We actually do that on our hardware and I know
> > others do, too.
> >
> > I asked about that back in 2019, see this thread:
> >
> > https://www.spinics.net/lists/linux-leds/msg11665.html
> >
> > At the time the multicolor framework was not yet merged, so today I would
> > probably make something which either uses the multicolor framework or at
> > least has a similar interface to userspace. However, it probably won't surprise
> > you all, this is not highest priority on my ToDo list. ;-)
> >
> > (What we actually do is pretend those are separate LEDs and ignore the
> > conflicting case where both GPIOs are on and the LED is dark then.)
> >
>
> Yes, that case seems conflict with mine, the pattern for me is like:
>
> P1 | P2 | LED
> -- + -- + -----
> 0 | 0 | off
> 0 | 1 | Any color
> 1 | 0 | Any color
> 1 | 1 | both on
>
> Now I'm investigate another way from Marek's suggestion by using REGULATOR_GPIO, to see if could meet my requirement. If yes, then I do think no new driver is needed.
Maybe you could even implement multicolor-gpio, now that we have
multicolor LED class :)
Marek
prev parent reply other threads:[~2021-03-12 9:04 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-11 13:04 [PATCH] leds: leds-dual-gpio: Add dual GPIO LEDs driver Hermes Zhang
2021-03-11 15:38 ` Marek Behun
2021-03-11 15:39 ` Marek Behun
2021-03-12 4:48 ` Hermes Zhang
2021-03-12 5:59 ` Marek Behun
2021-03-11 17:56 ` Pavel Machek
2021-03-11 18:02 ` Pavel Machek
2021-03-18 2:11 ` Hermes Zhang
2021-03-12 8:31 ` Alexander Dahl
2021-03-12 8:48 ` Hermes Zhang
2021-03-12 9:03 ` Marek Behun [this message]
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