regulator: dummy: convert to use the faux device interface

The dummy regulator driver does not need to create a platform device, it
only did so because it was simple to do.  Change it over to use the
faux bus instead as this is NOT a real platform device, and it makes
the code even smaller than before.

Reviewed-by: Mark Brown <broonie@kernel.org>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Link: https://lore.kernel.org/r/2025021027-outclass-stress-59dd@gregkh
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: gregkh

drivers/regulator/dummy.c

@@ -13,7 +13,7 @@
 
 #include <linux/err.h>
 #include <linux/export.h>
-#include <linux/platform_device.h>
+#include <linux/device/faux.h>
 #include <linux/regulator/driver.h>
 #include <linux/regulator/machine.h>
 
@@ -37,15 +37,15 @@ static const struct regulator_desc dummy_desc = {
 	.ops = &dummy_ops,
 };
 
-static int dummy_regulator_probe(struct platform_device *pdev)
+static int dummy_regulator_probe(struct faux_device *fdev)
 {
 	struct regulator_config config = { };
 	int ret;
 
-	config.dev = &pdev->dev;
+	config.dev = &fdev->dev;
 	config.init_data = &dummy_initdata;
 
-	dummy_regulator_rdev = devm_regulator_register(&pdev->dev, &dummy_desc,
+	dummy_regulator_rdev = devm_regulator_register(&fdev->dev, &dummy_desc,
 						       &config);
 	if (IS_ERR(dummy_regulator_rdev)) {
 		ret = PTR_ERR(dummy_regulator_rdev);
@@ -56,36 +56,17 @@ static int dummy_regulator_probe(struct platform_device *pdev)
 	return 0;
 }
 
-static struct platform_driver dummy_regulator_driver = {
-	.probe		= dummy_regulator_probe,
-	.driver		= {
-		.name		= "reg-dummy",
-		.probe_type	= PROBE_PREFER_ASYNCHRONOUS,
-	},
+struct faux_device_ops dummy_regulator_driver = {
+	.probe = dummy_regulator_probe,
 };
 
-static struct platform_device *dummy_pdev;
+static struct faux_device *dummy_fdev;
 
 void __init regulator_dummy_init(void)
 {
-	int ret;
-
-	dummy_pdev = platform_device_alloc("reg-dummy", -1);
-	if (!dummy_pdev) {
+	dummy_fdev = faux_device_create("reg-dummy", NULL, &dummy_regulator_driver);
+	if (!dummy_fdev) {
 		pr_err("Failed to allocate dummy regulator device\n");
 		return;
 	}
-
-	ret = platform_device_add(dummy_pdev);
-	if (ret != 0) {
-		pr_err("Failed to register dummy regulator device: %d\n", ret);
-		platform_device_put(dummy_pdev);
-		return;
-	}
-
-	ret = platform_driver_register(&dummy_regulator_driver);
-	if (ret != 0) {
-		pr_err("Failed to register dummy regulator driver: %d\n", ret);
-		platform_device_unregister(dummy_pdev);
-	}
 }