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

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Message-ID: <20210413084740.182cfc52@md1za8fc.ad001.siemens.net>
Date:   Tue, 13 Apr 2021 08:47:40 +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 20:34:45 +0300
schrieb Andy Shevchenko <andriy.shevchenko@...ux.intel.com>:

> 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.

Ok, just found that there is a null pointer deref in the probe function
of the pinctrl driver, looking into that.

Meanwhile i think i will need a similar patch for
pinctrl-sunrisepoint.c for that wdt, do you happen to have that as
well? Or a spec where to find all the magic numbers.

regards,
Henning

> 
> > 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.
>