Linux kernel “回声”；小号&燃气轮机；杂项字符驱动程序-被截断

我已经编写了一个misc char驱动程序，当我将驱动程序的次要编号回显到misc char驱动程序时，它不会收到第一个数字

写函数是这样的

static ssize_t hellowld_write(struct file *file, const char *buf,size_t len, 
                loff_t *ppos)
{
    pr_debug("In hellowld_write len %d buf %s \n",len,buf);
    minor[0] = '\0';    
    snprintf(minor, 20,"%d", hellowld_device.minor);
    strncpy(inputminor, buf,len);
    pr_debug("In hellowld_write -- minor %s -- recvNum  %s end\n",minor, inputminor);
    pr_debug("In hellowld_write -- strlen minor %d -- strlen inputminor  %d end\n", strlen(minor), strlen(inputminor));
    if( strncmp(minor, inputminor, strlen(minor)) ==  0)
    {
        pr_debug("In hellowld_write -- strcmp passed \n");
        return strlen(minor);   
    }
    else 
    {
        pr_debug("In hellowld_write -- strcmp failed \n");
        return -EFAULT;
    }   
}

当我这样做的时候， echo“54”>/dev/hellowld

Dec 31 11:36:40 pavan-linux kernel: [16981.382424] In hellowld_write len 1 buf 
Dec 31 11:36:40 pavan-linux kernel: [16981.382424] 
Dec 31 11:36:40 pavan-linux kernel: [16981.382424] o
Dec 31 11:36:40 pavan-linux kernel: [16981.382437] In hellowld_write -- minor 54 -- recvNum  
Dec 31 11:36:40 pavan-linux kernel: [16981.382437] 4
Dec 31 11:36:40 pavan-linux kernel: [16981.382437]  end
Dec 31 11:36:40 pavan-linux kernel: [16981.382444] In hellowld_write -- strlen minor 2 -- strlen inputminor  3 end
Dec 31 11:36:40 pavan-linux kernel: [16981.382448] In hellowld_write -- strcmp failed 

Dec 31 11:36:52 pavan-linux kernel: [16993.356993] In hellowld_write len 3 buf 22
Dec 31 11:36:52 pavan-linux kernel: [16993.356993] 
Dec 31 11:36:52 pavan-linux kernel: [16993.356993] o
Dec 31 11:36:52 pavan-linux kernel: [16993.357011] In hellowld_write -- minor 54 -- recvNum  22
Dec 31 11:36:52 pavan-linux kernel: [16993.357011]  end
Dec 31 11:36:52 pavan-linux kernel: [16993.357017] In hellowld_write -- strlen minor 2 -- strlen inputminor  3 end
Dec 31 11:36:52 pavan-linux kernel: [16993.357021] In hellowld_write -- strcmp failed 

echo“22”>/dev/hellowld

Dec 31 11:36:40 pavan-linux kernel: [16981.382424] In hellowld_write len 1 buf 
Dec 31 11:36:40 pavan-linux kernel: [16981.382424] 
Dec 31 11:36:40 pavan-linux kernel: [16981.382424] o
Dec 31 11:36:40 pavan-linux kernel: [16981.382437] In hellowld_write -- minor 54 -- recvNum  
Dec 31 11:36:40 pavan-linux kernel: [16981.382437] 4
Dec 31 11:36:40 pavan-linux kernel: [16981.382437]  end
Dec 31 11:36:40 pavan-linux kernel: [16981.382444] In hellowld_write -- strlen minor 2 -- strlen inputminor  3 end
Dec 31 11:36:40 pavan-linux kernel: [16981.382448] In hellowld_write -- strcmp failed 

Dec 31 11:36:52 pavan-linux kernel: [16993.356993] In hellowld_write len 3 buf 22
Dec 31 11:36:52 pavan-linux kernel: [16993.356993] 
Dec 31 11:36:52 pavan-linux kernel: [16993.356993] o
Dec 31 11:36:52 pavan-linux kernel: [16993.357011] In hellowld_write -- minor 54 -- recvNum  22
Dec 31 11:36:52 pavan-linux kernel: [16993.357011]  end
Dec 31 11:36:52 pavan-linux kernel: [16993.357017] In hellowld_write -- strlen minor 2 -- strlen inputminor  3 end
Dec 31 11:36:52 pavan-linux kernel: [16993.357021] In hellowld_write -- strcmp failed 

---

为什么当我回显次要数字时，hellowld_write中接收到的数据会被截断？

您的函数

hellowld_write

做了两件坏事：它直接访问

buf

（不从用户

copy_

），并且不返回值。请在测试中使用此函数的实现：

pr_debug（“在hellowld_write len%d\n中”，len）；回程透镜。您能发布完整的驱动程序代码吗？Tsyvarev的评论很有帮助