linux-kernel - Re: [PATCH v1 6/7] mfd: lpc_ich: Add support for pinctrl in non-ACPI system

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Date:   Mon, 12 Apr 2021 20:34:45 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Henning Schild <henning.schild@...mens.com>
Cc:     Wolfram Sang <wsa+renesas@...g-engineering.com>,
        Jean Delvare <jdelvare@...e.de>,
        Lee Jones <lee.jones@...aro.org>,
        Tan Jui Nee <jui.nee.tan@...el.com>,
        Jim Quinlan <james.quinlan@...adcom.com>,
        Jonathan Yong <jonathan.yong@...el.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        linux-kernel@...r.kernel.org, linux-i2c@...r.kernel.org,
        linux-pci@...r.kernel.org, Jean Delvare <jdelvare@...e.com>,
        Peter Tyser <ptyser@...-inc.com>, hdegoede@...hat.com
Subject: Re: [PATCH v1 6/7] mfd: lpc_ich: Add support for pinctrl in non-ACPI
 system

On Mon, Apr 12, 2021 at 07:16:53PM +0200, Henning Schild wrote:
> Am Mon, 12 Apr 2021 19:59:05 +0300
> schrieb Andy Shevchenko <andriy.shevchenko@...ux.intel.com>:
> > On Mon, Apr 12, 2021 at 06:40:01PM +0200, Henning Schild wrote:
> > > Tan or Andy,
> > > 
> > > maybe you can point me to a user of that patch. I guess there might
> > > be an out-of-tree driver or userland code on how to use the GPIOs
> > > from there.  
> > 
> > I'm confused. User of this patch is pinctrl-broxton driver.
> > It's in upstream.
> 
> Should this appear in /sys/class/gpio as chip so that pins can be
> exported?

No. Sysfs interface is deprecated. It should appear as /dev/gpiochip0 or so.

> That is what i tried and failed with.
> 
> > Using GPIOs from it is something as done in a few drivers already
> > (Assuming we have no resources described in the ACPI). I.e. you need
> > to register in board file the GPIO mapping table with help of
> > devm_acpi_dev_add_driver_gpios() and use one of gpiod_get() family of
> > functions to request it.
> > 
> > In case of LEDs you simple describe GPIO device name in lookup table
> > and that's it. The drivers/platform/x86/pcengines-apuv2.c not the
> > best but will give you an idea how to use "leds-gpio" driver in board
> > files.
> 
> I am aware of that driver and had a look at it. In order to figure out
> the arguments for the macros/functions i was hoping for userland gpio
> "export", but maybe that does not work here ...
> For now i will assume that it does not show up in sysfs and can maybe
> still be used, and try to build on top.

Just switch to use libgpiod and associated tools / bindings in user space.
Sysfs ABI is not being developed anymore.

-- 
With Best Regards,
Andy Shevchenko