[PATCH v1] ACPI: PAD: xen: Convert to a platform driver

["Rafael J. Wysocki" <rafael@xxxxxxxxxx>]

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

In all cases in which a struct acpi_driver is used for binding a driver
to an ACPI device object, a corresponding platform device is created by
the ACPI core and that device is regarded as a proper representation of
underlying hardware.  Accordingly, a struct platform_driver should be
used by driver code to bind to that device.  There are multiple reasons
why drivers should not bind directly to ACPI device objects [1].

Overall, it is better to bind drivers to platform devices than to their
ACPI companions, so convert the Xen ACPI processor aggregator device
(PAD) driver to a platform one.

While this is not expected to alter functionality, it changes sysfs
layout and so it will be visible to user space.

Link: https://lore.kernel.org/all/2396510.ElGaqSPkdT@rafael.j.wysocki/ [1]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
---

Note that the original ACPI PAD driver has been a platform driver for
quite some time already.

---
 drivers/xen/xen-acpi-pad.c | 23 ++++++++++++-----------
 1 file changed, 12 insertions(+), 11 deletions(-)

diff --git a/drivers/xen/xen-acpi-pad.c b/drivers/xen/xen-acpi-pad.c
index ede69a5278d3..75a39862c1df 100644
--- a/drivers/xen/xen-acpi-pad.c
+++ b/drivers/xen/xen-acpi-pad.c
@@ -11,6 +11,7 @@
 #include <linux/kernel.h>
 #include <linux/types.h>
 #include <linux/acpi.h>
+#include <linux/platform_device.h>
 #include <xen/xen.h>
 #include <xen/interface/version.h>
 #include <xen/xen-ops.h>
@@ -107,8 +108,9 @@ static void acpi_pad_notify(acpi_handle handle, u32 event,
        }
 }
 
-static int acpi_pad_add(struct acpi_device *device)
+static int acpi_pad_probe(struct platform_device *pdev)
 {
+       struct acpi_device *device = ACPI_COMPANION(&pdev->dev);
        acpi_status status;
 
        strcpy(acpi_device_name(device), ACPI_PROCESSOR_AGGREGATOR_DEVICE_NAME);
@@ -122,13 +124,13 @@ static int acpi_pad_add(struct acpi_device *device)
        return 0;
 }
 
-static void acpi_pad_remove(struct acpi_device *device)
+static void acpi_pad_remove(struct platform_device *pdev)
 {
        mutex_lock(&xen_cpu_lock);
        xen_acpi_pad_idle_cpus(0);
        mutex_unlock(&xen_cpu_lock);
 
-       acpi_remove_notify_handler(device->handle,
+       acpi_remove_notify_handler(ACPI_HANDLE(&pdev->dev),
                ACPI_DEVICE_NOTIFY, acpi_pad_notify);
 }
 
@@ -137,13 +139,12 @@ static const struct acpi_device_id pad_device_ids[] = {
        {"", 0},
 };
 
-static struct acpi_driver acpi_pad_driver = {
-       .name = "processor_aggregator",
-       .class = ACPI_PROCESSOR_AGGREGATOR_CLASS,
-       .ids = pad_device_ids,
-       .ops = {
-               .add = acpi_pad_add,
-               .remove = acpi_pad_remove,
+static struct platform_driver acpi_pad_driver = {
+       .probe = acpi_pad_probe,
+       .remove = acpi_pad_remove,
+       .driver = {
+               .name = "acpi_processor_aggregator",
+               .acpi_match_table = pad_device_ids,
        },
 };
 
@@ -157,6 +158,6 @@ static int __init xen_acpi_pad_init(void)
        if (!xen_running_on_version_or_later(4, 2))
                return -ENODEV;
 
-       return acpi_bus_register_driver(&acpi_pad_driver);
+       return platform_driver_register(&acpi_pad_driver);
 }
 subsys_initcall(xen_acpi_pad_init);
-- 
2.51.0