写入设备文件打印“无效参数”

Question

我目前正在使用设备驱动程序，在该驱动程序中我想为该驱动程序写一个句子并将其显示在内核中。读取内部缓冲区并用 cat 拨打驱动程序的工作状况非常好。但是，如果我尝试写入设备驱动程序，它将返回以下消息：

我为设备驱动程序有以下代码。我似乎找不到我在写功能中出错的地方...

#include "device_file.h"
#include <linux/fs.h>       /* file stuff */
#include <linux/kernel.h>   /* printk() */
#include <linux/errno.h>    /* error codes */
#include <linux/module.h>   /* THIS_MODULE */
#include <linux/cdev.h>     /* char device stuff */
#include <linux/uaccess.h>  /* copy_to_user() */

static const char g_s_Hello_World_string[] = "Hello from Job & Arief!\n\0";
static const ssize_t g_s_Hello_World_size = sizeof(g_s_Hello_World_string);
static char memory_buffer[500];

/*===============================================================================================*/
static ssize_t device_file_read(struct file *file_ptr, char __user *user_buffer, size_t count, loff_t *possition){

    printk( KERN_NOTICE "Kurniawan_Meulenbeld-driver: Device file is read at offset = %i, read bytes count = %u\n"
    , (int)*possition
    , (unsigned int)count );

    if( *possition >= g_s_Hello_World_size )
    return 0;

    if( *possition + count > g_s_Hello_World_size )
    count = g_s_Hello_World_size - *possition;

    if( copy_to_user(user_buffer, g_s_Hello_World_string + *possition, count) != 0 )
    return -EFAULT;

    *possition += count;
    return count;
}

/*===============================================================================================*/
static ssize_t memory_write( struct file *filp, const char *buf, size_t count, loff_t *f_pos) {
    const char *tmp;
    tmp=buf+count-1;

    if( copy_from_user(memory_buffer,tmp,1) != 0 )
        return -EFAULT;

    return count;
}
/*===============================================================================================*/
static struct file_operations Kurniawan_Meulenbeld_driver_fops =
        {
                .owner = THIS_MODULE,
                .read = device_file_read,
                .write =  memory_write,
        };

static int device_file_major_number = 0;
static const char device_name[] = "Kurniawan_Meulenbeld-driver";

/*===============================================================================================*/
int register_device(void)
{
    int result = 0;

    printk( KERN_NOTICE "Kurniawan_Meulenbeld-driver: register_device() is called.\n" );

    result = register_chrdev( 0, device_name, &Kurniawan_Meulenbeld_driver_fops );
    if( result < 0 )
    {
        printk( KERN_WARNING "Kurniawan_Meulenbeld-driver:  can\'t register character device with errorcode = %i\n", result );
        return result;
    }

    device_file_major_number = result;
    printk( KERN_NOTICE "Kurniawan_Meulenbeld-driver: registered character device with major number = %i and minor numbers 0...255\n"
            , device_file_major_number );

    return 0;
}

/*===============================================================================================*/
void unregister_device(void)
{
    printk( KERN_NOTICE "Kurniawan_Meulenbeld-driver: unregister_device() is called\n" );
    if(device_file_major_number != 0)
    {
        unregister_chrdev(device_file_major_number, device_name);
    }
}

Answer 1

请注意，重定向＆gt;/dev/my-driver是由当前用户下的shell在调用sudo之前完成的。 einval来自 写 含义 fd已连接到不适合编写的对象上。

尚不清楚Hello是文件还是字符串。 CAT期望它是文件。

要在设备中写下字符串 Hello 尝试：

echo "hello" | sudo tee /dev/my-driver

在设备中写文件 Hello 尝试：

cat hello | sudo tee /dev/my-driver
# or
sudo tee /dev/my-driver <hello