linux driver 寫入 - Linux

不知道在這裡問這個對不對，最近在研究撰寫linux driver，找到一些網路上簡單的範例
但那些範例一次只能寫入一筆資料，我想一次能寫入多筆資料然後讀出來
可是怎麼改都不對...

以下是一些程式碼：

ssize_t dev_write(struct file *filp, const char __user *buf, size_t count,
loff_t *f_pos)
{
struct dev_data *p = filp->private_data;
unsigned char val[5];
int retval = 0, i;

printk("%s: count %d pos %lld\n", __func__, count, *f_pos);

for(i=0;i<count;i++){
if (copy_from_user(&val[i], &buf[i], 1)) {
retval = -EFAULT;
goto out;
}
}

write_lock(&p->lock);
for(i=0;i<5;i++)
p->val[i] = val[i];
write_unlock(&p->lock);
retval = count;
out:
return (retval);
}


ssize_t dev_read(struct file *filp, char __user *buf, size_t count, loff_t
*f_pos)
{
struct dev_data *p = filp->private_data;
unsigned char val[5];
int retval, i;

read_lock(&p->lock);
for(i=0;i<5;i++)
val[i] = p->val[i];
read_unlock(&p->lock);

printk("%s: count %d pos %lld\n", __func__, count, *f_pos);

for (i = 0 ; i < count ; i++) {
if (copy_to_user(&buf[i], &val[i], 1)) {
retval = -EFAULT;
goto out;
}
}

retval = count;
out:
return (retval);
}

TEST:

write_file(fd, "01234");
read_file(fd);

void write_file(int fd, unsigned char *val)
{
ssize_t ret;

ret = write(fd, &val, 5);
if (ret <= 0) {
perror("write");
}
}

void read_file(int fd)
{
unsigned char buf[5], *p;
ssize_t ret;

ret = read(fd, buf, sizeof(buf));
if (ret > 0) {
p = buf;
while (ret--)
printf("%02x ", *p++);
} else {
perror("read");
}

printf("\n");
}

我想要出現30 31 32 33 34但是卻不是，到底哪裡有問題?

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