linux-kernel - Re: How to use an ACPI declared GPIO in a userspace ...

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Date:   Fri, 2 Oct 2020 16:23:32 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Flavio Suligoi <f.suligoi@...m.it>
Cc:     Bartosz Golaszewski <brgl@...ev.pl>,
        "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
        "linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: How to use an ACPI declared GPIO in a userspace ...

On Fri, Oct 2, 2020 at 3:48 PM Andy Shevchenko
<andy.shevchenko@...il.com> wrote:
>
> On Fri, Oct 2, 2020 at 1:02 PM Flavio Suligoi <f.suligoi@...m.it> wrote:
>
> > > > > My SSDT table is:
> > > >
> > > > ^^^^ See the difference? I can't help here.
> >
> > This is the DSDT table related to the GPIO controller of my board:
> >
> > Device (GPO1)
> >         {
> >             Name (_ADR, Zero)  // _ADR: Address
> >             Name (_HID, "INT3452")  // _HID: Hardware ID
> >             Name (_CID, "INT3452")  // _CID: Compatible ID
> >             Name (_DDN, "General Purpose Input/Output (GPIO) Controller - Northwest")  // _DDN: DOS Device Name
> >             Name (_UID, 0x02)  // _UID: Unique ID
> >             Name (RBUF, ResourceTemplate ()
> >             {
> >                 Memory32Fixed (ReadWrite,
> >                     0x00000000,         // Address Base
> >                     0x00004000,         // Address Length
> >                     _Y08)
> >                 Interrupt (ResourceConsumer, Level, ActiveLow, Shared, ,, )
> >                 {
> >                     0x0000000E,
> >                 }
> >             })
> >             Method (_CRS, 0, NotSerialized)  // _CRS: Current Resource Settings
> >             {
> >                 CreateDWordField (RBUF, \_SB.GPO1._Y08._BAS, B0BA)  // _BAS: Base Address
> >                 CreateDWordField (RBUF, \_SB.GPO1._Y08._LEN, B0LN)  // _LEN: Length
> >                 B0BA = GP1A /* \GP1A */
> >                 B0LN = GP1L /* \GP1L */
> >                 Return (RBUF) /* \_SB_.GPO1.RBUF */
> >             }
> >
> >             Method (_STA, 0, NotSerialized)  // _STA: Status
> >             {
> >                 If ((OSYS < 0x07DC))
> >                 {
> >                     Return (Zero)
> >                 }
> >
> >                 Return (0x0F)
> >             }
> >         }
>
> So, what about adding the following
>
> DefinitionBlock ("linename.aml", "SSDT", 5, "", "LINENAME", 1)
> {
>   External (_SB_.GPO1, DeviceObj)
>   Scope (\_SB.GPO1)
>   {
>       Name (_DSD, Package () {
>           ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
>           Package () {
>               Package () {
>                   "gpio-line-names",
>                   Package () {
>                       "Line0",
>                       "Line1",
>                       "Line2",
>                       ...
>                   }
>               },
>           }
>       })
>   }
> }
>
> ?
>
> (Replace '...' with meaningful line names or drop for now, but in any
> case you need to provide as much names as lines of such GPIO
> controller)

I have checked the code, so it allows you to define from 0 up to all
lines, but no gaps.
Thus, I have dropped '...' line in above excerpt, added the compiled
AML to initramfs (initrd method) and voila!

% gpioinfo gpiochip1
gpiochip1 - 77 lines:
       line   0:      "Line0"       unused   input  active-high
       line   1:      "Line1"       unused   input  active-high
       line   2:      "Line2"       unused   input  active-high
       line   3:      unnamed       unused   input  active-high


% gpiofind Line2
gpiochip1 2

Of course you may convert _DSD to be a Method and fill the line names
dynamically with help of ASL.

-- 
With Best Regards,
Andy Shevchenko