[PATCH v9 3/5] EINJ: Migrate to a platform driver

[Ben Cheatham <Benjamin.Cheatham@amd.com>]

Change the EINJ module to install a platform device/driver on module
init and move the module init() and exit() functions to driver probe and
remove. This change allows the EINJ module to load regardless of whether
setting up EINJ succeeds, which allows dependent modules to still load
(i.e. the CXL core).

Since EINJ may no longer be initialized when the module loads, any
functions that are called from dependent/external modules should check
the einj_initialized variable before calling any EINJ functions.

Signed-off-by: Ben Cheatham <Benjamin.Cheatham@amd.com>
---
 drivers/acpi/apei/einj.c | 43 ++++++++++++++++++++++++++++++++++++++--
 1 file changed, 41 insertions(+), 2 deletions(-)

diff --git a/drivers/acpi/apei/einj.c b/drivers/acpi/apei/einj.c
index 013eb621dc92..10d51cd73fa4 100644
--- a/drivers/acpi/apei/einj.c
+++ b/drivers/acpi/apei/einj.c
@@ -21,6 +21,7 @@
 #include <linux/nmi.h>
 #include <linux/delay.h>
 #include <linux/mm.h>
+#include <linux/platform_device.h>
 #include <asm/unaligned.h>
 
 #include "apei-internal.h"
@@ -136,6 +137,12 @@ static struct apei_exec_ins_type einj_ins_type[] = {
  */
 static DEFINE_MUTEX(einj_mutex);
 
+/*
+ * Functions called from dependent modules should check this variable
+ * before using any EINJ functionality.
+ */
+static bool einj_initialized;
+
 static void *einj_param;
 
 static void einj_exec_ctx_init(struct apei_exec_context *ctx)
@@ -684,7 +691,7 @@ static int einj_check_table(struct acpi_table_einj *einj_tab)
 	return 0;
 }
 
-static int __init einj_init(void)
+static int einj_probe(struct platform_device *pdev)
 {
 	int rc;
 	acpi_status status;
@@ -782,7 +789,7 @@ static int __init einj_init(void)
 	return rc;
 }
 
-static void __exit einj_exit(void)
+static void einj_remove(struct platform_device *pdev)
 {
 	struct apei_exec_context ctx;
 
@@ -801,6 +808,38 @@ static void __exit einj_exit(void)
 	acpi_put_table((struct acpi_table_header *)einj_tab);
 }
 
+static struct platform_device *einj_dev;
+struct platform_driver einj_driver = {
+	.remove_new = einj_remove,
+	.driver = {
+		.name = "einj",
+	},
+};
+
+static int __init einj_init(void)
+{
+	struct platform_device_info einj_dev_info = {
+		.name = "einj",
+		.id = -1,
+	};
+
+	einj_dev = platform_device_register_full(&einj_dev_info);
+	einj_initialized = !platform_driver_probe(&einj_driver, einj_probe);
+
+	if (!(einj_initialized || IS_ERR_OR_NULL(einj_dev)))
+		platform_device_del(einj_dev);
+
+	return 0;
+}
+
+static void __exit einj_exit(void)
+{
+	if (einj_initialized) {
+		platform_driver_unregister(&einj_driver);
+		platform_device_del(einj_dev);
+	}
+}
+
 module_init(einj_init);
 module_exit(einj_exit);
 
-- 
2.34.1