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From: "Andrew Jeffery" <firstname.lastname@example.org>
To: "Andy Shevchenko" <email@example.com>
Cc: "firstname.lastname@example.org" <email@example.com>,
"Cédric Le Goater" <firstname.lastname@example.org>,
"Rob Herring" <email@example.com>,
"Joel Stanley" <firstname.lastname@example.org>, "Pavel Machek" <email@example.com>,
"Linus Walleij" <firstname.lastname@example.org>,
Subject: Re: [RFC PATCH 0/6] leds: Fix pca955x GPIO pin mappings
Date: Wed, 28 Jul 2021 15:13:24 +0930 [thread overview]
Message-ID: <email@example.com> (raw)
On Fri, 23 Jul 2021, at 17:45, Andy Shevchenko wrote:
> On Friday, July 23, 2021, Andrew Jeffery <firstname.lastname@example.org> wrote:
> > Hello,
> > This series does a bunch of crimes, so it's an RFC. I'm cross-posting to the
> > pinctrl/GPIO and LEDs lists because the PCA955x devices impact all of them. What
> > needs fixing is the leds-pca955x driver's failure to map the GPIO numberspace to
> > the pin numberspace of the PCA955x devices. The series solves that by
> > implementing pinctrl and pinmux in the leds-pca955x driver.
> > Things I'm unsure about:
> > 1. Patch 1: The pinctrl_gpio_as_pin() API feels a bit dirty, not sure what
> > others thoughts are on that (Linus?).
> > 2. Patch 2: I've added a new callback to hook the entirety of the pinctrl map
> > parsing rather than supplying a subnode-specific callback. This was necessary
> > to handle the PCA955x devicetree binding in a backwards compatible way.
> > 3. Patch 4: The PCA955x devices don't actually have any pinmux hardware, but the
> > properties of the pinctrl/pinmux subsystems in the kernel map nicely onto the
> > problem we have. But it's quite a bit of code...
> > 4. Patch 6: I also lost a bunch of time to overlooking the get_group_pins()
> > callback for pinctrl, and it seems odd to me that it isn't required.
> > Please review!
> Sounds like a hack.
Yes, possibly. Feedback like this is why I sent the series as an RFC.
> 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). 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
next prev parent reply other threads:[~2021-07-28 5:43 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-23 7:58 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 ` Andrew Jeffery [this message]
2021-07-28 9:13 ` [RFC PATCH 0/6] leds: Fix pca955x GPIO pin mappings Andy Shevchenko
2021-07-29 0:38 ` Andrew Jeffery
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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