linux-kernel - Re: [PATCH v1 1/2] usb: core: acpi: Use the sysdev pointer instead of controller device

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Date:   Tue, 26 Apr 2022 12:18:24 +0200
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Heikki Krogerus <heikki.krogerus@...ux.intel.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Felipe Balbi <balbi@...nel.org>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Mathias Nyman <mathias.nyman@...ux.intel.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        USB <linux-usb@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1 1/2] usb: core: acpi: Use the sysdev pointer instead of
 controller device

On Mon, Apr 25, 2022 at 3:41 PM Heikki Krogerus
<heikki.krogerus@...ux.intel.com> wrote:
>
> The controller device (hcd) does not always have the ACPI
> companion assigned to it at all. We can not rely on it when
> finding the ACPI companion for the root hub. Instead we need
> to use the sysdev pointer here.

...

>         if (!udev->parent) {
>                 /* root hub is only child (_ADR=0) under its parent, the HC */

I believe the comment can be amended now to point out that we use the
physical device representing the parent of this child, and not
(always) a direct parent of the device in terms of Linux device model.

> -               adev = ACPI_COMPANION(udev->dev.parent);
> +               adev = ACPI_COMPANION(udev->bus->sysdev);
>                 return acpi_find_child_device(adev, 0, false);
>         }


-- 
With Best Regards,
Andy Shevchenko