字符设备文件操作write的count传入总是为0?

mmkiller

自做字符驱动，文件操作函数write：

static ssize_t
my_write(struct file *filp, const char *buff, size_t count, loff_t *off)
{
     char mybuff[4000];
     int c;

     c = count;
     memset(mybuff, 0, sizeof(mybuff));
     copy_from_user(mybuff, buff, 100);
     DBG("writting: %s, filp = %X, pos = %d, count = %d\n", mybuff, (unsigned int)filp, (unsigned int)*off, c);
     return count;
}

无论写入什么内容，count 总是为0，为什么会这样？

mmkiller

已解决。..