Linux操作系统内核和设备文件对话(1)(4)

int i;

char *temp;

#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,2,0)

char ch;

#endif

/* Switch according to the ioctl called */

switch (ioctl_num) {

case IOCTL_SET_MSG:

/* Receive a pointer to a message (in user space)

* and set that to be the devices message. */

/* Get the parameter given to ioctl by the process */

temp = (char *) ioctl_param;

/* Find the length of the message */

#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,2,0)

get_user(ch, temp);

for (i=0; ch && ibr temp++) i++,> get_user(ch, temp);

#else

for (i=0; get_user(temp) && ibr temp++) i++,> ;

#endif

/* Dont reinvent the wheel - call device_write */

#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,2,0)

device_write(file, (char *) ioctl_param, i, 0);

#else

device_write(inode, file, (char *) ioctl_param, i);

#endif

break;

case IOCTL_GET_MSG:

/* Give the current message to the calling

* process - the parameter we got is a pointer,

* fill it. */

#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,2,0)

i = device_read(file, (char *) ioctl_param, 99, 0);

#else

i = device_read(inode, file, (char *) ioctl_param,

99);

#endif

/* Warning - we assume here the buffer length is

* 100. If its less than that we might overflow

* the buffer, causing the process to core dump.

*

* The reason we only allow up to 99 characters is

* that the NULL which terminates the string also

* needs room. */

/* Put a zero at the end of the buffer, so it

* will be properly terminated */

put_user(\, (char *) ioctl_param+i);

break;

case IOCTL_GET_NTH_BYTE:

/* This ioctl is both input (ioctl_param) and

* output (the return value of this function) */

return Message[ioctl_param];

break;

}

return SUCCESS;

}