linux-kernel - [PATCH v2 7/8] ACPI: APEI: EINJ: Transition to the faux device interface

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Message-Id: <20250318-plat2faux_dev-v2-7-e6cc73f78478@arm.com>
Date: Tue, 18 Mar 2025 17:01:45 +0000
From: Sudeep Holla <sudeep.holla@....com>
To: linux-kernel@...r.kernel.org
Cc: Sudeep Holla <sudeep.holla@....com>, 
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
 "Rafael J. Wysocki" <rafael@...nel.org>, Borislav Petkov <bp@...en8.de>, 
 linux-acpi@...r.kernel.org
Subject: [PATCH v2 7/8] ACPI: APEI: EINJ: Transition to the faux device
 interface

The APEI error injection driver does not require the creation of a
platform device. Originally, this approach was chosen for simplicity
when the driver was first implemented.

With the introduction of the lightweight faux device interface, we now
have a more appropriate alternative. Migrate the driver to utilize the
faux bus, given that the platform device it previously created was not
a real one anyway. This will simplify the code, reducing its footprint
while maintaining functionality.

Cc: "Rafael J. Wysocki" <rafael@...nel.org>
Cc: Borislav Petkov <bp@...en8.de>
Cc: linux-acpi@...r.kernel.org
Signed-off-by: Sudeep Holla <sudeep.holla@....com>
---
 drivers/acpi/apei/einj-core.c | 51 +++++--------------------------------------
 1 file changed, 6 insertions(+), 45 deletions(-)

diff --git a/drivers/acpi/apei/einj-core.c b/drivers/acpi/apei/einj-core.c
index 04731a5b01faaba534bad853d0acc4c8a873a53b..5fddd01074bafab2f7b23fd7ef9f863c0856637b 100644
--- a/drivers/acpi/apei/einj-core.c
+++ b/drivers/acpi/apei/einj-core.c
@@ -21,7 +21,7 @@
 #include <linux/nmi.h>
 #include <linux/delay.h>
 #include <linux/mm.h>
-#include <linux/platform_device.h>
+#include <linux/device/faux.h>
 #include <linux/unaligned.h>
 
 #include "apei-internal.h"
@@ -749,7 +749,7 @@ static int einj_check_table(struct acpi_table_einj *einj_tab)
 	return 0;
 }
 
-static int __init einj_probe(struct platform_device *pdev)
+static int __init einj_probe(struct faux_device *fdev)
 {
 	int rc;
 	acpi_status status;
@@ -838,6 +838,8 @@ static int __init einj_probe(struct platform_device *pdev)
 
 	pr_info("Error INJection is initialized.\n");
 
+	einj_initialized = true;
+
 	return 0;
 
 err_release:
@@ -851,7 +853,7 @@ static int __init einj_probe(struct platform_device *pdev)
 	return rc;
 }
 
-static void __exit einj_remove(struct platform_device *pdev)
+static void __exit einj_remove(struct faux_device *fdev)
 {
 	struct apei_exec_context ctx;
 
@@ -872,48 +874,7 @@ static void __exit einj_remove(struct platform_device *pdev)
 	acpi_put_table((struct acpi_table_header *)einj_tab);
 }
 
-static struct platform_device *einj_dev;
-/*
- * einj_remove() lives in .exit.text. For drivers registered via
- * platform_driver_probe() this is ok because they cannot get unbound at
- * runtime. So mark the driver struct with __refdata to prevent modpost
- * triggering a section mismatch warning.
- */
-static struct platform_driver einj_driver __refdata = {
-	.remove = __exit_p(einj_remove),
-	.driver = {
-		.name = "acpi-einj",
-	},
-};
-
-static int __init einj_init(void)
-{
-	struct platform_device_info einj_dev_info = {
-		.name = "acpi-einj",
-		.id = -1,
-	};
-	int rc;
-
-	einj_dev = platform_device_register_full(&einj_dev_info);
-	if (IS_ERR(einj_dev))
-		return PTR_ERR(einj_dev);
-
-	rc = platform_driver_probe(&einj_driver, einj_probe);
-	einj_initialized = rc == 0;
-
-	return 0;
-}
-
-static void __exit einj_exit(void)
-{
-	if (einj_initialized)
-		platform_driver_unregister(&einj_driver);
-
-	platform_device_unregister(einj_dev);
-}
-
-module_init(einj_init);
-module_exit(einj_exit);
+module_faux_driver(acpi_einj, einj_probe, __exit_p(einj_remove), true);
 
 MODULE_AUTHOR("Huang Ying");
 MODULE_DESCRIPTION("APEI Error INJection support");

-- 
2.34.1