From: "Andrew Jeffery" <andrew@aj.id.au>
To: "Andy Shevchenko" <andy.shevchenko@gmail.com>
Cc: "linux-leds@vger.kernel.org" <linux-leds@vger.kernel.org>,
"linux-gpio@vger.kernel.org" <linux-gpio@vger.kernel.org>,
"Cédric Le Goater" <clg@kaod.org>,
"Rob Herring" <robh+dt@kernel.org>,
"Joel Stanley" <joel@jms.id.au>, "Pavel Machek" <pavel@ucw.cz>,
"Linus Walleij" <linus.walleij@linaro.org>,
"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
"linux-aspeed@lists.ozlabs.org" <linux-aspeed@lists.ozlabs.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [RFC PATCH 0/6] leds: Fix pca955x GPIO pin mappings
Date: Thu, 29 Jul 2021 10:08:38 +0930 [thread overview]
Message-ID: <6cc64039-f82a-4c1e-ad2c-16fad7aa3178@www.fastmail.com> (raw)
In-Reply-To: <CAHp75Vc2W+WmwNj1AvH6EiT_80c+5gADV9QzK+asHxpd1Ucppw@mail.gmail.com>
On Wed, 28 Jul 2021, at 18:43, Andy Shevchenko wrote:
> On Wed, Jul 28, 2021 at 8:43 AM Andrew Jeffery <andrew@aj.id.au> wrote:
> > On Fri, 23 Jul 2021, at 17:45, Andy Shevchenko wrote:
> >
> > > I was briefly looking into patches 1-4 and suddenly
> > > realized that the fix can be similar as in PCA9685 (PWM), I.e. we
> > > always have chips for the entire pin space and one may map them
> > > accordingly, requested in one realm (LED) in the other (GPIO)
> > > automatically is BUSY. Or I missed the point?
> >
> > No, you haven't missed the point. I will look at the PCA9685 driver.
> >
> > That said, my goal was to implement the behaviour intended by the
> > existing binding (i.e. fix a bug).
>
> Okay, so it implies that this used to work at some point.
I don't think this is true. It only "works" if the lines specified as
GPIO in the devicetree are contiguous from line 0. That way the pin and
GPIO number spaces align. I suspect that's all that's been tested up
until this point.
We now have a board with a PCA9552 where the first 8 pins are LED and
the last 8 pins are GPIO, and if you specify this in the devicetree
according to the binding you hit the failure to map between the two
number spaces.
> What has
> changed from that point? Why can't we simply fix the culprit commit?
As such nothing has changed, I think it's always been broken, just we
haven't had hardware configurations that demonstrated the failure.
>
> > However, userspace would never have
> > got the results it expected with the existing driver implementation, so
> > I guess you could argue that no such (useful) userspace exists. Given
> > that, we could adopt the strategy of always defining a gpiochip
> > covering the whole pin space, and parts of the devicetree binding just
> > become redundant.
>
> I'm lost now. GPIO has its own userspace ABI, how does it work right
> now in application to this chip?
As above, it "works" if the GPIOs specified in the devicetree are
contiguous from line 0. It's broken if they're not.
Andrew
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next prev parent reply other threads:[~2021-07-29 0:41 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-23 7:58 [RFC PATCH 0/6] leds: Fix pca955x GPIO pin mappings Andrew Jeffery
2021-07-23 7:58 ` [RFC PATCH 1/6] pinctrl: Add pinctrl_gpio_as_pin() Andrew Jeffery
2021-08-10 13:34 ` Linus Walleij
2021-08-11 0:24 ` Andrew Jeffery
2021-07-23 7:58 ` [RFC PATCH 2/6] pinctrl: Add hook for device-specific map parsing Andrew Jeffery
2021-07-23 7:58 ` [RFC PATCH 3/6] leds: pca955x: Relocate chipdef-related descriptors Andrew Jeffery
2021-07-23 7:58 ` [RFC PATCH 4/6] leds: pca955x: Use pinctrl to map GPIOs to pins Andrew Jeffery
2021-08-10 13:54 ` Linus Walleij
2021-08-11 0:19 ` Andrew Jeffery
2021-07-23 7:58 ` [RFC PATCH 5/6] ARM: dts: rainier: Add presence-detect and fault indictor GPIO expander Andrew Jeffery
2021-07-23 7:58 ` [RFC PATCH 6/6] pinctrl: Check get_group_pins callback on init Andrew Jeffery
[not found] ` <CAHp75VeQML7njMZ6x8kC-ZJVexC1xJ6n1cB3JneVMAVfuOJgWw@mail.gmail.com>
2021-07-28 5:43 ` [RFC PATCH 0/6] leds: Fix pca955x GPIO pin mappings Andrew Jeffery
2021-07-28 9:13 ` Andy Shevchenko
2021-07-29 0:38 ` Andrew Jeffery [this message]
2021-07-29 7:40 ` Andy Shevchenko
2021-08-03 4:07 ` Andrew Jeffery
2021-08-03 10:33 ` Andy Shevchenko
2021-08-04 4:55 ` Andrew Jeffery
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