linux-kernel - Re: [PATCH v1 00/16] ACPI: Get rid of the list of children in struct acpi

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Message-ID: <YqINyDTfpNBGDYlb@smile.fi.intel.com>
Date:   Thu, 9 Jun 2022 18:12:08 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Frank Rowand <frank.rowand@...y.com>,
        Rob Herring <robh@...nel.org>
Cc:     Linux ACPI <linux-acpi@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Hans de Goede <hdegoede@...hat.com>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>
Subject: Re: [PATCH v1 00/16] ACPI: Get rid of the list of children in struct
 acpi_device

On Thu, Jun 09, 2022 at 03:44:27PM +0200, Rafael J. Wysocki wrote:
> Hi All,
> 
> Confusingly enough, the ACPI subsystem stores the information on the given ACPI
> device's children in two places: as the list of children in struct acpi_device
> and (as a result of device registration) in the list of children in the embedded
> struct device.
> 
> These two lists agree with each other most of the time, but not always (like in
> error paths in some cases), and the list of children in struct acpi_device is
> not generally safe to use without locking.  In principle, it should always be
> walked under acpi_device_lock, but in practice holding acpi_scan_lock is
> sufficient for that too.  However, its users may not know whether or not
> they operate under acpi_scan_lock and at least in some cases it is not accessed
> in a safe way (note that ACPI devices may go away as a result of hot-remove,

> unlike OF nodes).

Hmm... Does it true for DT overlays? Not an expert in DT overlays, though,
adding Rob and Frank.

> For this reason, it is better to consolidate the code that needs to walk the
> children of an ACPI device which is the purpose of this patch series.
> 
> Overall, it switches over all of the users of the list of children in struct
> acpi_device to using helpers based on the driver core's mechanics and finally
> drops that list, but some extra cleanups are done on the way.
> 
> Please refer to the patch changelogs for details.

I'm going to look the individual patches.

-- 
With Best Regards,
Andy Shevchenko