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

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Message-ID: <1843211.tdWV9SEqCh@kreacher>
Date:   Thu, 09 Jun 2022 15:44:27 +0200
From:   "Rafael J. Wysocki" <rjw@...ysocki.net>
To:     Linux ACPI <linux-acpi@...r.kernel.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Hans de Goede <hdegoede@...hat.com>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>
Subject: [PATCH v1 00/16] ACPI: Get rid of the list of children in struct acpi_device

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).

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.

Thanks!