作者future314 (未来π)
看板Linux
标题[问题] linux driver 写入
时间Wed Mar 18 00:47:29 2015
不知道在这里问这个对不对，最近在研究撰写linux driver，找到一些网路上简单的范例
但那些范例一次只能写入一笔资料，我想一次能写入多笔资料然後读出来
可是怎麽改都不对...
以下是一些程式码：
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");
}
我想要出现30 31 32 33 34但是却不是，到底哪里有问题?
--
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※ 编辑: future314 (1.168.74.55), 03/18/2015 00:54:40
1F：→ future314: 好吧...自己找到答案了 原来是在test里 write function 03/18 20:58
2F：→ future314: &val要改成val不然会把地址传出...简单的C语言问题... 03/18 21:00
3F：→ future314: 在dev_write中也不用回圈收值 直接pass 5 bytes就好了 03/18 21:01