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From: Andy Shevchenko <andy.shevchenko@gmail.com>
To: Andrew Jeffery <andrew@aj.id.au>
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: Tue, 3 Aug 2021 13:33:38 +0300	[thread overview]
Message-ID: <CAHp75Ve-6zKE9UX+LR022cGAA6xvd8CeLnnKE_fT3snnzmNusA@mail.gmail.com> (raw)
In-Reply-To: <50aaf381-8cda-4656-9222-f23fda75d3bc@www.fastmail.com>

On Tue, Aug 3, 2021 at 7:07 AM Andrew Jeffery <andrew@aj.id.au> wrote:
> On Thu, 29 Jul 2021, at 17:10, Andy Shevchenko wrote:
> > On Thu, Jul 29, 2021 at 3:39 AM Andrew Jeffery <andrew@aj.id.au> wrote:
> > > 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:
> > > > > 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.
> >
> > So, "it never works" means there is no bug. Now, what we need is to
> > keep the same enumeration scheme, but if you wish to be used half/half
> > (or any other ratio), the driver should do like the above mentioned
> > PWM, i.e. register entire space and depending on the requestor either
> > proceed with a line or mark it as BUSY.
> >
> > Ideally, looking into what the chip can do, this should be indeed
> > converted to some like pin control + PWM + LED + GPIO drivers. Then
> > the function in pin mux configuration can show what exactly is enabled
> > on the certain line(s).
>
> So just to clarify, you want both solutions here?
>
> 1. A gpiochip that covers the entire pin space
> 2. A pinmux implementation that manages pin allocation to the different drivers
>
> In that case we can largely leave this series as is? We only need to
> adjust how we configure the gpiochip by dropping the pin-mapping
> implementation?

Nope. It's far from what I think of. Re-reading again your cover
letter it points out that pin mux per se does not exist in the
hardware. In this case things become a bit too complicated, but we
still may manage to handle them. Before I was thinking about this
hierarchy

1. pinmux driver (which is actually the main driver here)
2. LED driver (using regmap API)
3. GPIO driver (via gpio-regmap)
4. PWM driver.

Now what we need here is some kind of "virtual" pinmux. Do I
understand correctly?

To be clear: I do not like putting everything into one driver when the
logical parts may be separated.

-- 
With Best Regards,
Andy Shevchenko

  reply	other threads:[~2021-08-03 10:34 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   ` [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
2021-07-29  7:40         ` Andy Shevchenko
2021-08-03  4:07           ` Andrew Jeffery
2021-08-03 10:33             ` Andy Shevchenko [this message]
2021-08-04  4:55               ` Andrew Jeffery

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