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From:   "Rafael J. Wysocki" <rjw@rjwysocki.net>
To:     Linux ACPI <linux-acpi@vger.kernel.org>
Cc:     LKML <linux-kernel@vger.kernel.org>,
        Linux PM <linux-pm@vger.kernel.org>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        Mika Westerberg <mika.westerberg@linux.intel.com>,
        Hans de Goede <hdegoede@redhat.com>,
        Sakari Ailus <sakari.ailus@linux.intel.com>,
        Lee Jones <lee.jones@linaro.org>
Subject: [PATCH v2 13/16] mfd: core: Use acpi_dev_for_each_child()
Date:   Mon, 13 Jun 2022 20:31:08 +0200
Message-ID: <2726954.BEx9A2HvPv@kreacher>
In-Reply-To: <2653857.mvXUDI8C0e@kreacher>
References: <1843211.tdWV9SEqCh@kreacher> <2653857.mvXUDI8C0e@kreacher>
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From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Instead of walking the list of children of an ACPI device directly,
use acpi_dev_for_each_child() to carry out an action for all of
the given ACPI device's children.

This will help to eliminate the children list head from struct
acpi_device as it is redundant and it is used in questionable ways
in some places (in particular, locking is needed for walking the
list pointed to it safely, but it is often missing).

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
---

v1 -> v2:
   * Add R-by from Andy.

---
 drivers/mfd/mfd-core.c |   31 ++++++++++++++++++++++++-------
 1 file changed, 24 insertions(+), 7 deletions(-)

Index: linux-pm/drivers/mfd/mfd-core.c
===================================================================
--- linux-pm.orig/drivers/mfd/mfd-core.c
+++ linux-pm/drivers/mfd/mfd-core.c
@@ -60,12 +60,29 @@ int mfd_cell_disable(struct platform_dev
 EXPORT_SYMBOL(mfd_cell_disable);
 
 #if IS_ENABLED(CONFIG_ACPI)
+struct match_ids_walk_data {
+	struct acpi_device_id *ids;
+	struct acpi_device *adev;
+};
+
+static int match_device_ids(struct acpi_device *adev, void *data)
+{
+	struct match_ids_walk_data *wd = data;
+
+	if (!acpi_match_device_ids(adev, wd->ids)) {
+		wd->adev = adev;
+		return 1;
+	}
+
+	return 0;
+}
+
 static void mfd_acpi_add_device(const struct mfd_cell *cell,
 				struct platform_device *pdev)
 {
 	const struct mfd_cell_acpi_match *match = cell->acpi_match;
-	struct acpi_device *parent, *child;
 	struct acpi_device *adev = NULL;
+	struct acpi_device *parent;
 
 	parent = ACPI_COMPANION(pdev->dev.parent);
 	if (!parent)
@@ -83,14 +100,14 @@ static void mfd_acpi_add_device(const st
 	if (match) {
 		if (match->pnpid) {
 			struct acpi_device_id ids[2] = {};
+			struct match_ids_walk_data wd = {
+				.adev = NULL,
+				.ids = ids,
+			};
 
 			strlcpy(ids[0].id, match->pnpid, sizeof(ids[0].id));
-			list_for_each_entry(child, &parent->children, node) {
-				if (!acpi_match_device_ids(child, ids)) {
-					adev = child;
-					break;
-				}
-			}
+			acpi_dev_for_each_child(parent, match_device_ids, &wd);
+			adev = wd.adev;
 		} else {
 			adev = acpi_find_child_device(parent, match->adr, false);
 		}