From c00edd6c4c9d300bc721328de2f4aa299db24839 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Christian=20L=C3=B6pke?= <loepke@edfritsch.de>
Date: Sun, 1 May 2016 10:54:30 +0200
Subject: [PATCH] Created modified version of chardev-1 which is able to hold a
given name and make personalized outputs.
---
20160425/Makefile | 1 +
20160425/chardev-1write.c | 205 ++++++++++++++++++++++++++++++++++++++
2 files changed, 206 insertions(+)
create mode 100644 20160425/chardev-1write.c
diff --git a/20160425/Makefile b/20160425/Makefile
index 263a0a5..6075827 100644
--- a/20160425/Makefile
+++ b/20160425/Makefile
@@ -1,5 +1,6 @@
obj-m += hellomod-1.o
obj-m += chardev-1.o
+obj-m += chardev-1write.o
all:
make -C /lib/modules/$(shell uname -r)/build M=$(PWD) modules
diff --git a/20160425/chardev-1write.c b/20160425/chardev-1write.c
new file mode 100644
index 0000000..bb6c15e
--- /dev/null
+++ b/20160425/chardev-1write.c
@@ -0,0 +1,205 @@
+/* Modified by: Christian Löpke <christian.loepke@hs-bochum.de>
+ * chardev-1write.c: Creates a char device that says Mr. Anderson or a
+ * written name how many times he read from the dev
+ * file.
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/fs.h>
+#include <asm/uaccess.h> /* for put_user */
+
+/*
+ * Prototypes - this would normally go in a .h file
+ */
+int init_module(void);
+void cleanup_module(void);
+static int device_open(struct inode *, struct file *);
+static int device_release(struct inode *, struct file *);
+static ssize_t device_read(struct file *, char *, size_t, loff_t *);
+static ssize_t device_write(struct file *, const char *, size_t, loff_t *);
+
+#define SUCCESS 0
+#define DEVICE_NAME "chardev" /* Dev name as it appears in /proc/devices */
+#define BUF_LEN 80 /* Max length of the message from the device */
+#define USERBUF_LEN 20 /* Max length for user definable name */
+/*
+ * Global variables are declared as static, so are global within the file.
+ */
+
+static int Major; /* Major number assigned to our device driver */
+static int Device_Open = 0; /* Is device open?
+ * Used to prevent multiple access to device */
+static char msg[BUF_LEN]; /* The msg the device will give when asked */
+static char *msg_Ptr; /* The current char from msg we are writing */
+
+static char msg_username[USERBUF_LEN]; /* User definable name */
+static int told_you_counter = 0; /* Counts the outputs I've made */
+
+static struct file_operations fops = {
+ .read = device_read,
+ .write = device_write,
+ .open = device_open,
+ .release = device_release
+};
+
+/*
+ * This function is called when the module is loaded
+ */
+int init_module(void)
+{
+ Major = register_chrdev(0, DEVICE_NAME, &fops);
+
+ if (Major < 0) {
+ printk( KERN_ALERT
+ "%s: Registering char device failed with %d\n",
+ DEVICE_NAME,
+ Major);
+ return Major;
+ }
+
+ printk( KERN_INFO "%s: I was assigned major number %d. To talk to\n",
+ DEVICE_NAME,
+ Major);
+ printk( KERN_INFO
+ "%s: the driver, create a dev file with\n", DEVICE_NAME);
+ printk( KERN_INFO "%s: 'mknod /dev/%s c %d 0'.\n",
+ DEVICE_NAME,
+ DEVICE_NAME,
+ Major);
+ printk( KERN_INFO
+ "%s: Try various minor numbers. Try to cat and echo to\n",
+ DEVICE_NAME);
+ printk( KERN_INFO "%s: the device file.\n", DEVICE_NAME);
+ printk( KERN_INFO
+ "%s: Remove the device file and module when done.\n",
+ DEVICE_NAME);
+
+ sprintf(msg_username, "Mr. Anderson"); //Setup initial username.
+ return SUCCESS;
+}
+
+/*
+ * This function is called when the module is unloaded
+ */
+void cleanup_module(void)
+{
+ /*
+ * Unregister the device
+ */
+ unregister_chrdev(Major, DEVICE_NAME);
+}
+
+/*
+ * Methods
+ */
+
+/*
+ * Called when a process tries to open the device file, like
+ * "cat /dev/mycharfile"
+ */
+static int device_open(struct inode *inode, struct file *file)
+{
+ if (Device_Open)
+ return -EBUSY;
+
+ Device_Open++;
+ sprintf(msg,
+ "I already told you %d times Hello world!, %s.\n",
+ told_you_counter++,
+ msg_username);
+ msg_Ptr = msg;
+ try_module_get(THIS_MODULE);
+
+ return SUCCESS; /* Device successfully opened */
+}
+
+/*
+ * Called when a process closes the device file.
+ */
+static int device_release(struct inode *inode, struct file *file)
+{
+ Device_Open--; /* We're now ready for our next caller */
+
+ /*
+ * Decrement the usage count, or else once you opened the file, you'll
+ * never get get rid of the module.
+ */
+ module_put(THIS_MODULE);
+
+ return 0; /* Device sucessfully closed */
+}
+
+/*
+ * Called when a process, which already opened the dev file, attempts to
+ * read from it.
+ */
+static ssize_t device_read(struct file *filp, /* see include/linux/fs.h */
+ char *buffer, /* buffer to fill with data */
+ size_t length, /* length of the buffer */
+ loff_t * offset)
+{
+ /*
+ * Number of bytes actually written to the buffer
+ */
+ int bytes_read = 0;
+
+ /*
+ * If we're at the end of the message,
+ * return 0 signifying end of file
+ */
+ if (*msg_Ptr == 0)
+ return 0;
+
+ /*
+ * Actually put the data into the buffer
+ */
+ while (length && *msg_Ptr) {
+
+ /*
+ * The buffer is in the user data segment, not the kernel
+ * segment so "*" assignment won't work. We have to use
+ * put_user which copies data from the kernel data segment to
+ * the user data segment.
+ */
+ put_user(*(msg_Ptr++), buffer++);
+
+ length--;
+ bytes_read++;
+ }
+
+ /*
+ * Most read functions return the number of bytes put into the buffer
+ */
+ return bytes_read;
+}
+
+/*
+ * Called when a process writes to dev file: echo "hi" > /dev/hello
+ */
+static ssize_t
+device_write(struct file *filp, const char *buff, size_t len, loff_t * off)
+{
+ /* Since nobody wants to read I have to correct the already told you
+ counter! */
+ told_you_counter--;
+ if(len > USERBUF_LEN) {
+ printk( KERN_WARNING
+ "%s: Sorry, your input is too long. Max %d allowed!\n",
+ DEVICE_NAME,
+ USERBUF_LEN);
+ return -ENOMEM; //Return not enaugh memory
+ }
+ else {
+ int i;
+ for(i = 0; i < len; i++) //Save the given string
+ msg_username[i] = buff[i];
+ for(i = len; i < USERBUF_LEN; i++) //Zeroing out the rest of mem
+ msg_username[i] = 0;
+ printk( KERN_INFO "%s: Successfully got %d bytes!\n",
+ DEVICE_NAME, (int)len);
+ if(msg_username[len-1] == '\n') //Got new line terminator ?
+ msg_username[len-1] = 0; //Then terminate it!
+ return len; //Emit successfully stored len bytes
+ }
+}
--
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