BeagleBoneBlueTutorial/0003-Use-linkded-list-in-hello-module.patch at master · HosseinAssaran/BeagleBoneBlueTutorial · GitHub

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From c2d433810a89fe6606b605803a16f90de6bbe70d Mon Sep 17 00:00:00 2001
From: "Hossein.Assaran" <Hossein.Assaran@gmail.com>
Date: Fri, 10 Jul 2020 12:01:58 +0430
Subject: [PATCH] Use linkded list in hello module

---
 drivers/test-module/hello.c | 54 ++++++++++++++++++++++---------------
 1 file changed, 32 insertions(+), 22 deletions(-)

diff --git a/drivers/test-module/hello.c b/drivers/test-module/hello.c
index 64918bf03..68363245f 100644
--- a/drivers/test-module/hello.c
+++ b/drivers/test-module/hello.c
@@ -4,6 +4,7 @@
 #include <linux/kernel.h>
 #include <linux/slab.h>
 #include <linux/string.h>
+#include <linux/list.h>

 static char *string = "Hello world";
 module_param(string,charp,S_IRUSR | S_IWUSR);
@@ -13,7 +14,7 @@ static int count = 5;
 module_param(count, int, S_IRUSR | S_IWUSR);
 MODULE_PARM_DESC(count, "The number of objects");

-static char **string_list = 0;
+static LIST_HEAD(device_list);

 int add(int a, int b)
 {
@@ -24,6 +25,7 @@ EXPORT_SYMBOL(add);
 typedef struct my_dev {
 	 char *name;
 	 int id;
+	 struct list_head node;
 }my_dev;

 static int count_backup;
@@ -31,54 +33,62 @@ static int __init hello_init(void)
 {
 	int i = 0;
 	int ret_code = 0;
+	struct my_dev *dev = 0;
+	struct list_head *cursor = 0, *tmp = 0;
+	char *name = 0;
 	if (count <0)
 		count = 0;
 	if (count > 9999)
 		count = 9999;
-	string_list = kcalloc(count, sizeof(char*), GFP_KERNEL);
-	if (!string_list){
-		 pr_alert("No memo!\n");
-		 ret_code = -ENOMEM;
-		 goto exit_point1;
-	}
-	char *name = kmalloc(sizeof("device_0000"), GFP_KERNEL);
-	count_backup = count;
+	name = kmalloc(sizeof("device_0000"), GFP_KERNEL);
 	if(!name){
 		pr_alert("No memory!\n");
 		ret_code = -ENOMEM;
 		goto exit_point;
 	}
 	for (i = 0; i < count ; i++) {
+		dev = kzalloc(sizeof(struct my_dev), GFP_KERNEL);
 		sprintf(name, "device_%04d", i);
-		string_list[i] = kstrdup(name, GFP_KERNEL);
-        pr_alert("Adding new device: %s\n", string_list[i]);
-		if (!string_list[i]){
+        pr_alert("Adding new device: %s\n", name);
+		dev->id = i;
+		dev->name = kstrdup(name, GFP_KERNEL);
+		if (!dev->name){
 			 pr_alert("No Memory for %d-th object\n", i);
 			ret_code = -ENOMEM;
 			goto exit_point;
 		}
+		list_add_tail(&dev->node, &device_list);
 	}

 exit_point:
 	kfree (name);
 	if(ret_code && i){
-		do{
-			kfree(string_list[--i]);
-		}while(i);
-		kfree(string_list);
+		list_for_each_safe(cursor, tmp, &device_list){
+			dev = list_entry(cursor, struct my_dev, node);
+			list_del(&dev->node);
+			kfree(dev->name);
+			kfree(dev);
+		}
 	}
-exit_point1:
 	return ret_code;
 }

 static void __exit hello_exit(void)
 {
-	int i;
-	for (i = 0; i < count_backup; i++){
-		pr_alert("device name %d = %s\n", i, string_list[i]);
-		kfree(string_list[i]);
+	struct list_head *cursor, *tmp;
+	struct my_dev *dev;
+	list_for_each_safe(cursor, tmp, &device_list){
+		dev = list_entry(cursor, struct my_dev, node);
+		pr_alert("device id=%d, name= %s\n", dev->id, dev->name);
+		list_del(&dev->node);
+		kfree(dev->name);
+		kfree(dev);
 	}
-	kfree(string_list);
+	if(!list_empty(&device_list))
+		pr_alert("Why am I here!\n");
+	else
+		pr_alert("The list is empty\n");
+
 	pr_alert("Good bye the string was %s\n", string);
 }

--
2.17.1