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Date: Mon, 29 Apr 2024 09:29:42 +0100
From: Jonathan Cameron <Jonathan.Cameron@Huawei.com>
To: "Rafael J. Wysocki" <rjw@rjwysocki.net>
CC: Linux ACPI <linux-acpi@vger.kernel.org>, LKML
	<linux-kernel@vger.kernel.org>, Salil Mehta <salil.mehta@huawei.com>
Subject: Re: [PATCH v1] ACPI: scan: Avoid enumerating devices with clearly
 invalid _STA values
Message-ID: <20240429092942.00004c96@Huawei.com>
In-Reply-To: <2741433.mvXUDI8C0e@kreacher>
References: <2741433.mvXUDI8C0e@kreacher>
Organization: Huawei Technologies Research and Development (UK) Ltd.
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On Fri, 26 Apr 2024 18:56:21 +0200
"Rafael J. Wysocki" <rjw@rjwysocki.net> wrote:

> From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> 
> The return value of _STA with the "present" bit unset and the "enabled"
> bit set is clearly invalid as per the ACPI specification, Section 6.3.7
> "_STA (Device Status)", so make the ACPI device enumeration code
> disregard devices with such _STA return values.
> 
> Also, because this implies that status.enabled will only be set if
> status.present is set too, acpi_device_is_enabled() can be modified
> to simply return the value of the former.
> 
> Link: https://uefi.org/specs/ACPI/6.5/06_Device_Configuration.html#sta-device-status
> Link: https://lore.kernel.org/linux-acpi/88179311a503493099028c12ca37d430@huawei.com/
> Suggested-by: Salil Mehta <salil.mehta@huawei.com>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Seems a sensible tidying up.  Hopefully nothing was relying on
this looser behavior.  One trivial thing inline.

Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

> ---
>  drivers/acpi/bus.c  |   11 +++++++++++
>  drivers/acpi/scan.c |    2 +-
>  2 files changed, 12 insertions(+), 1 deletion(-)
> 
> Index: linux-pm/drivers/acpi/bus.c
> ===================================================================
> --- linux-pm.orig/drivers/acpi/bus.c
> +++ linux-pm/drivers/acpi/bus.c
> @@ -112,6 +112,17 @@ int acpi_bus_get_status(struct acpi_devi
>  	if (ACPI_FAILURE(status))
>  		return -ENODEV;
>  
> +	if (!device->status.present && device->status.enabled) {
> +		pr_info(FW_BUG "Device [%s] status [%08x]: not present and enabled\n",
> +			device->pnp.bus_id, (u32)sta);
> +		device->status.enabled = 0;
> +		/*
> +		 * The status is clearly invalid, so clear the enabled bit as
> +		 * well to avoid attempting to use the device.
> +		 */

Comment seems to be in a slightly odd place.  Perhaps one line earlier makes
more sense?  Or was the intent to mention functional here?

> +		device->status.functional = 0;
> +	}
> +
>  	acpi_set_device_status(device, sta);
>  
>  	if (device->status.functional && !device->status.present) {
> Index: linux-pm/drivers/acpi/scan.c
> ===================================================================
> --- linux-pm.orig/drivers/acpi/scan.c
> +++ linux-pm/drivers/acpi/scan.c
> @@ -1962,7 +1962,7 @@ bool acpi_device_is_present(const struct
>  
>  bool acpi_device_is_enabled(const struct acpi_device *adev)
>  {
> -	return adev->status.present && adev->status.enabled;
> +	return adev->status.enabled;
>  }
>  
>  static bool acpi_scan_handler_matching(struct acpi_scan_handler *handler,
> 
> 
>