Энциклопедия разработчика модулей ядра Linux

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 return bytes_read;

}

/* This function is called when somebody tries to write into our device file. */

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

static ssize_t device_write(struct file *file, const char *buffer, size_t length, loff_t *offset)

#else

static int device_write(struct inode *inode, struct file *file, const char *buffer, int length)

#endif

{

 int i;

#ifdef DEBUG

 printk("device_write(%p,%s,%d)", file, buffer, length);

#endif

 for(i=0; i<length && i<BUF_LEN; i++)

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

get_user(Message[i], buffer+i);

#else

Message[i] = get_user(buffer+i);

#endif

 Message_Ptr = Message;

 /* Again, return the number of input characters used */

 return i;

}

/* This function is called whenever a process tries to

* do an ioctl on our device file. We get two extra

* parameters (additional to the inode and file

* structures, which all device functions get): the number

* of the ioctl called and the parameter given to the ioctl function.

*

* If the ioctl is write or read/write (meaning output

* is returned to the calling process), the ioctl call

* returns the output of this function. */

int device_ioctl(struct inode *inode, struct file *file,

 unsigned int ioctl_num, /* The number of the ioctl */

 unsigned long ioctl_param) /* The parameter to it */

{

 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 device's 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 && i<BUF_LEN; i++, temp++) get_user(ch, temp);

#else

for (i=0; get_user(temp) && i<BUF_LEN; i++, temp++) ;

#endif

/* Don't 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 it's 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('\0', (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;

}

/* Module Declarations *************************** */

/* This structure will hold the functions to be called

* when a process does something to the device we

* created. Since a pointer to this structure is kept in

* the devices table, it can't be local to

* init_module. NULL is for unimplemented functions. */