linux-kernel - Re: [PATCH v1] ACPI: scan: Avoid enumerating devices with clearly invalid

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Date: Mon, 29 Apr 2024 18:07:32 +0200
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Jonathan Cameron <Jonathan.Cameron@...wei.com>
Cc: "Rafael J. Wysocki" <rjw@...ysocki.net>, Linux ACPI <linux-acpi@...r.kernel.org>, 
	LKML <linux-kernel@...r.kernel.org>, Salil Mehta <salil.mehta@...wei.com>
Subject: Re: [PATCH v1] ACPI: scan: Avoid enumerating devices with clearly
 invalid _STA values

On Mon, Apr 29, 2024 at 10:29 AM Jonathan Cameron
<Jonathan.Cameron@...wei.com> wrote:
>
> On Fri, 26 Apr 2024 18:56:21 +0200
> "Rafael J. Wysocki" <rjw@...ysocki.net> wrote:
>
> > From: Rafael J. Wysocki <rafael.j.wysocki@...el.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@...wei.com>
> > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> Seems a sensible tidying up.  Hopefully nothing was relying on
> this looser behavior.  One trivial thing inline.
>
> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>

Thanks!

> > ---
> >  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?

Rui has noticed this already.

I thought "functional" and wrote "enabled".  Oh well, I'll send a v2.

> > +             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,
> >
> >
> >
>
>