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

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Date:   Wed, 30 Sep 2020 15:39:13 +0000
From:   Flavio Suligoi <f.suligoi@...m.it>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
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 ...

Hi Andy,

> I guess you simply didn't get. The "gpio-line-names" property of GPIO
> *controller* (provider!) and you are trying to do something with the
> *consumer*
> if I got it right.
> 
> And of course GPIO line, which has name, has no difference in use from
> another
> w/o name assigned. You will need to request it by *consumer* either in
> kernel
> or in user space.
> 
> To be more precise we have to look at your DSDT.
> 
> --
> With Best Regards,
> Andy Shevchenko
> 

My SSDT table is:

DefinitionBlock ("gpio_button.aml", "SSDT", 5, "ASEMsp", "GPIO_BTN", 1)
{
	External (_SB_.GPO1, DeviceObj)

	Scope (\_SB.GPO1)
	{
		Device (BTNS)
		{
			Name (_HID, "PRP0001")
			Name (_DDN, "GPIO buttons device")

			Name (_CRS, ResourceTemplate ()
			{
				GpioIo (
				Exclusive,               // Not shared
				PullNone,                // No need for pulls
				0,                       // Debounce timeout
				0,                       // Drive strength
				IoRestrictionInputOnly,  // Only used as input
				"\\_SB.GPO1",            // GPIO controller
				0, ResourceConsumer, , ) // Must be 0
				{
					1,              // GPIO number
				}
			})
	
			Name (_DSD, Package () {
				ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
				Package () {
					Package () {
						"gpio-line-names",
						Package () {
							"USER_PUSH_BUTTON",
						}
					},
				}
			})
		}
	}
}

And the kernel messages, after loading the table, are:

ACPI: Host-directed Dynamic ACPI Table Load:
ACPI: SSDT 0xFFFF908274285200 0000E8 (v05 ASEMsp GPIO_BTN 00000001 INTL 20200717)
ACPI: \_SB_.GPO1.BTNS: PRP0001 requires 'compatible' property

So I need a "consumer", but I don't want to export the GPIO using its number...
If you have any suggestion ...

Thanks!

Flavi