[PATCH v1 2/3] ACPI: platform: Use acpi_bus_get_primary_device()

["Rafael J. Wysocki" <rafael@kernel.org>]

From: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>

The acpi_get_first_physical_node() usage in acpi_platform_fill_resource()
and acpi_create_platform_device() is generally unsafe because in theory
the device returned by it may be freed at any time [1].

It is also inefficient because acpi_get_first_physical_node() is called
multiple times for the same argument which can be avoided.

Address these issues by using acpi_bus_get_primary_device() instead of
acpi_get_first_physical_node() and adjusting the code to call it just
once at the beginning of and acpi_create_platform_device() and drop
the device reference acquired by it upon the return from that function.

Fixes: 3b95bd160547 ("ACPI: introduce a function to find the first physical device")
Fixes: a252d881c558 ("ACPI / platform: Pay attention to parent device's resources")
Link: https://sashiko.dev/#/patchset/12955541.O9o76ZdvQC%40rafael.j.wysocki [1]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---
 drivers/acpi/acpi_platform.c |   16 +++++++---------
 1 file changed, 7 insertions(+), 9 deletions(-)

--- a/drivers/acpi/acpi_platform.c
+++ b/drivers/acpi/acpi_platform.c
@@ -102,18 +102,15 @@ static unsigned int acpi_platform_adjust
 	return count;
 }
 
-static void acpi_platform_fill_resource(struct acpi_device *adev,
-	const struct resource *src, struct resource *dest)
+static void acpi_platform_fill_resource(struct device *parent,
+					const struct resource *src,
+					struct resource *dest)
 {
-	struct device *parent;
-
 	*dest = *src;
-
 	/*
 	 * If the device has parent we need to take its resources into
 	 * account as well because this device might consume part of those.
 	 */
-	parent = acpi_get_first_physical_node(acpi_dev_parent(adev));
 	if (parent && dev_is_pci(parent))
 		dest->parent = pci_find_resource(to_pci_dev(parent), dest);
 }
@@ -141,7 +138,8 @@ static unsigned int acpi_platform_resour
 struct platform_device *acpi_create_platform_device(struct acpi_device *adev,
 						    const struct property_entry *properties)
 {
-	struct acpi_device *parent = acpi_dev_parent(adev);
+	struct acpi_device *p = acpi_dev_parent(adev);
+	struct device *parent __free(put_device) = acpi_bus_get_primary_device(p);
 	struct platform_device *pdev = NULL;
 	struct platform_device_info pdevinfo;
 	const struct acpi_device_id *match;
@@ -187,7 +185,7 @@ struct platform_device *acpi_create_plat
 								       rentry->res,
 								       resources,
 								       count);
-				acpi_platform_fill_resource(adev, rentry->res,
+				acpi_platform_fill_resource(parent, rentry->res,
 							    &resources[count++]);
 			}
 			acpi_dev_free_resource_list(&resource_list);
@@ -200,7 +198,7 @@ struct platform_device *acpi_create_plat
 	 * attached to it, that physical device should be the parent of the
 	 * platform device we are about to create.
 	 */
-	pdevinfo.parent = parent ? acpi_get_first_physical_node(parent) : NULL;
+	pdevinfo.parent = parent;
 	pdevinfo.name = dev_name(&adev->dev);
 	pdevinfo.id = PLATFORM_DEVID_NONE;
 	pdevinfo.res = resources;