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 19:16:53 +0200
From:   Henning Schild <henning.schild@...mens.com>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.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

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?

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.

regards,
Henning

> 
> > Feel free to send directly to me in case it is not published
> > anywhere and should not yet be on the list, i could just use it for
> > inspiration. A driver will likely be GPL anyways.  
>