linux-kernel - Re: [PATCH] ACPI: glue: Use acpi_device_adr() in acpi_find_child

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Message-ID: <YXmJjlY6+oFy4siX@smile.fi.intel.com>
Date:   Wed, 27 Oct 2021 20:17:02 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:     Linux ACPI <linux-acpi@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Hans de Goede <hdegoede@...hat.com>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>
Subject: Re: [PATCH] ACPI: glue: Use acpi_device_adr() in
 acpi_find_child_device()

On Wed, Oct 27, 2021 at 06:59:06PM +0200, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> Instead of evaluating _ADR in acpi_find_child_device(), use the
> observation that it has already been evaluated and the value returned
> by it has been stored in the pnp.type.bus_address field of the ACPI
> device object at hand.

...

> +		acpi_bus_address addr = acpi_device_adr(adev);
>  		int score;
>  
> -		status = acpi_evaluate_integer(adev->handle, METHOD_NAME__ADR,
> -					       NULL, &addr);
> -		if (ACPI_FAILURE(status) || addr != address)
> +		if (!adev->pnp.type.bus_address || addr != address)
>  			continue;

I'm not sure I understand the new check, i.e. !adev->pnp.type.bus_address.
IIUC _ADR == 0 is a valid value and children may have it like this.

I believe this change will break the working things (first comes to my mind
is drivers/mfd/intel_quark_i2c_gpio.c).

-- 
With Best Regards,
Andy Shevchenko