Added buffer length to proc entry.

[cascardo/kernel/samples/02.char/.git] / helloc.c

diff --git a/helloc.c b/helloc.c
index f43a767..b0271df 100644 (file)
--- a/helloc.c
+++ b/helloc.c
@@ -6,6 +6,8 @@
 /* Needed for copying to/from user space */
 #include <asm/uaccess.h>
 #include <linux/slab.h>
+#include <linux/proc_fs.h>
+#include <linux/seq_file.h>
 
 MODULE_LICENSE("GPL");
 MODULE_AUTHOR("Thadeu Lima de Souza Cascardo <cascardo@holoscopio.com>");
@@ -31,6 +33,14 @@ static int helloc_open(struct inode *ino, struct file *filp)
                return -ENODEV;
        msg = hello_message[iminor(ino)];
        filp->private_data = msg;
+       if (filp->f_flags & O_TRUNC) {
+               memset(msg->text, 0, msg->len);
+               msg->len = 0;
+               printk(KERN_INFO "File opened with truncate flags\n");
+       }
+       if (filp->f_flags & O_APPEND) {
+               filp->f_pos = msg->len;
+       }
        return 0;
 }
 
@@ -67,18 +77,27 @@ static ssize_t helloc_write(struct file *filp, const char __user *buf,
        int r;
        struct message *msg = filp->private_data;
        /* do not read pass through the size of the message */
-       if (*pos >= msg->len)
+       if (*pos >= BUFFER_SIZE)
        /* return end of file */
                return 0;
        /* if len is bigger than the rest of the message, clamp it */
-       if (len > msg->len - *pos)
-               len = msg->len - *pos;
+       if (len > BUFFER_SIZE - *pos)
+               len = BUFFER_SIZE - *pos;
+
        /* copy message to user space and return error if it fails */
        r = copy_from_user(msg->text + *pos, buf, len);
-       if (r)
+       if (r) {
+               if (*pos + len > msg->len)
+                       memset(msg->text + msg->len, 0, *pos + len - msg->len);
                return -EFAULT;
+       }
        /* update the file position */
        *pos += len;
+       if (msg->len < *pos) {
+               printk(KERN_DEBUG "Updating size from %d to %lld\n", msg->len, *pos);
+               msg->len = *pos;
+       }
+
        return len;
 }
 
@@ -91,6 +110,27 @@ static struct file_operations helloc_fops = {
        .write = helloc_write,
 };
 
+static int hello_len_show(struct seq_file *seq, void *data)
+{
+       struct message *msg = seq->private;
+       seq_printf(seq, "%d\n", msg->len);
+       return 0;
+}
+
+static int hello_proc_open(struct inode *ino, struct file *filp)
+{
+       return single_open(filp, hello_len_show, hello_message[0]);
+}
+
+static struct file_operations hello_proc_fops = {
+       .owner = THIS_MODULE,
+       .open = hello_proc_open,
+       .llseek = seq_lseek,
+       .read = seq_read,
+       .release = seq_release,
+};
+
+
 /* the device number and the char device struct */
 static dev_t dev;
 static struct cdev *cdev;
@@ -128,6 +168,7 @@ out:
 
 static int __init helloc_init(void)
 {
+       struct proc_dir_entry *hello_pde;
        int r;
        r = helloc_alloc();
        if (r)
@@ -150,7 +191,12 @@ static int __init helloc_init(void)
        r = cdev_add(cdev, dev, DEVICE_NUMBER);
        if (r)
                goto out_add;
+       hello_pde = proc_create("hello_len", 0666, NULL, &hello_proc_fops);
+       if (!hello_pde)
+               goto out_pde;
        return 0;
+out_pde:
+       cdev_del(cdev);
 out_add:
        /* release memory allocated to the cdev device */
        kfree(cdev);
@@ -164,6 +210,7 @@ out_alloc2:
 
 static void __exit helloc_exit(void)
 {
+       remove_proc_entry("hello_len", NULL);
        /* remove the chardev from the system */
        cdev_del(cdev);
        /* release the device number allocated */