ACPI: NFIT: core: Convert the driver to a platform one

While binding drivers directly to struct acpi_device objects allows
basic functionality to be provided, at least in the majority of cases,
there are some problems with it, related to general consistency, sysfs
layout, power management operation ordering, and code cleanliness.

Overall, it is better to bind drivers to platform devices than to their
ACPI companions, so convert the ACPI NFIT core 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.

This change was mostly developed by Michal Wilczynski [1].

Linu: https://lore.kernel.org/linux-acpi/20231011083334.3987477-6-michal.wilczynski@intel.com/ [1]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Link: https://patch.msgid.link/6221453.lOV4Wx5bFT@rafael.j.wysocki
Acked-by: Ira Weiny <ira.weiny@intel.com>
Tested-by: Ira Weiny <ira.weiny@intel.com>

Author: rafaeljw

drivers/acpi/nfit/core.c

@@ -2,6 +2,7 @@
 /*
  * Copyright(c) 2013-2015 Intel Corporation. All rights reserved.
  */
+#include <linux/platform_device.h>
 #include <linux/list_sort.h>
 #include <linux/libnvdimm.h>
 #include <linux/module.h>
@@ -89,15 +90,22 @@ static const guid_t *to_nfit_bus_uuid(int family)
 static struct acpi_device *to_acpi_dev(struct acpi_nfit_desc *acpi_desc)
 {
 	struct nvdimm_bus_descriptor *nd_desc = &acpi_desc->nd_desc;
+	struct acpi_device *adev;
 
-	/*
-	 * If provider == 'ACPI.NFIT' we can assume 'dev' is a struct
-	 * acpi_device.
-	 */
+	/* If provider == 'ACPI.NFIT', a struct acpi_device is there. */
 	if (!nd_desc->provider_name
 			|| strcmp(nd_desc->provider_name, "ACPI.NFIT") != 0)
 		return NULL;
 
+	/*
+	 * But it can be the ACPI companion of acpi_desc->dev when it cones from
+	 * acpi_nfit_probe().
+	 */
+	adev = ACPI_COMPANION(acpi_desc->dev);
+	if (adev)
+		return adev;
+
+	/* Or it is acpi_desc->dev itself when it comes from nfit_ctl_test(). */
 	return to_acpi_device(acpi_desc->dev);
 }
 
@@ -3283,11 +3291,11 @@ static void acpi_nfit_put_table(void *table)
 
 static void acpi_nfit_notify(acpi_handle handle, u32 event, void *data)
 {
-	struct acpi_device *adev = data;
+	struct device *dev = data;
 
-	device_lock(&adev->dev);
-	__acpi_nfit_notify(&adev->dev, handle, event);
-	device_unlock(&adev->dev);
+	device_lock(dev);
+	__acpi_nfit_notify(dev, handle, event);
+	device_unlock(dev);
 }
 
 static void acpi_nfit_remove_notify_handler(void *data)
@@ -3328,18 +3336,19 @@ void acpi_nfit_shutdown(void *data)
 }
 EXPORT_SYMBOL_GPL(acpi_nfit_shutdown);
 
-static int acpi_nfit_add(struct acpi_device *adev)
+static int acpi_nfit_probe(struct platform_device *pdev)
 {
 	struct acpi_buffer buf = { ACPI_ALLOCATE_BUFFER, NULL };
 	struct acpi_nfit_desc *acpi_desc;
-	struct device *dev = &adev->dev;
+	struct device *dev = &pdev->dev;
+	struct acpi_device *adev = ACPI_COMPANION(dev);
 	struct acpi_table_header *tbl;
 	acpi_status status = AE_OK;
 	acpi_size sz;
 	int rc = 0;
 
 	rc = acpi_dev_install_notify_handler(adev, ACPI_DEVICE_NOTIFY,
-					     acpi_nfit_notify, adev);
+					     acpi_nfit_notify, dev);
 	if (rc)
 		return rc;
 
@@ -3369,7 +3378,7 @@ static int acpi_nfit_add(struct acpi_device *adev)
 	acpi_desc = devm_kzalloc(dev, sizeof(*acpi_desc), GFP_KERNEL);
 	if (!acpi_desc)
 		return -ENOMEM;
-	acpi_nfit_desc_init(acpi_desc, &adev->dev);
+	acpi_nfit_desc_init(acpi_desc, dev);
 
 	/* Save the acpi header for exporting the revision via sysfs */
 	acpi_desc->acpi_header = *tbl;
@@ -3474,11 +3483,11 @@ static const struct acpi_device_id acpi_nfit_ids[] = {
 };
 MODULE_DEVICE_TABLE(acpi, acpi_nfit_ids);
 
-static struct acpi_driver acpi_nfit_driver = {
-	.name = KBUILD_MODNAME,
-	.ids = acpi_nfit_ids,
-	.ops = {
-		.add = acpi_nfit_add,
+static struct platform_driver acpi_nfit_driver = {
+	.probe = acpi_nfit_probe,
+	.driver = {
+		.name = "acpi-nfit",
+		.acpi_match_table = acpi_nfit_ids,
 	},
 };
 
@@ -3516,7 +3525,7 @@ static __init int nfit_init(void)
 		return -ENOMEM;
 
 	nfit_mce_register();
-	ret = acpi_bus_register_driver(&acpi_nfit_driver);
+	ret = platform_driver_register(&acpi_nfit_driver);
 	if (ret) {
 		nfit_mce_unregister();
 		destroy_workqueue(nfit_wq);
@@ -3529,7 +3538,7 @@ static __init int nfit_init(void)
 static __exit void nfit_exit(void)
 {
 	nfit_mce_unregister();
-	acpi_bus_unregister_driver(&acpi_nfit_driver);
+	platform_driver_unregister(&acpi_nfit_driver);
 	destroy_workqueue(nfit_wq);
 	WARN_ON(!list_empty(&acpi_descs));
 }