> struct file *file, /* The file itself */
> const char *buf, /* The buffer with the input */
> int length) /* The buffer's length */
>#endif
>{
> int i;
> /* Put the input into Message, where module_output
> * will later be able to use it */
> for(i=0; i
>#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,2,0)
> get_user(Message[i], buf+i);
>#else
> Message[i] = get_user(buf+i);
>#endif
> /* we want a standard, zero terminated string */
> Message[i] = '\0';
> /* We need to return the number of input characters used */
> return i;
>}
>/* 1 if the file is currently open by somebody */
>int Already_Open = 0;
> /* Queue of processes who want our file */
>static struct wait_queue *WaitQ = NULL;
>/* Called when the /proc file is opened */
>static int module_open(struct inode *inode, struct file *file) {
> /* If the file's flags include O_NONBLOCK, it means
> * the process doesn't want to wait for the file.
> * In this case, if the file is already open, we
> * should fail with -EAGAIN, meaning "you'll have to
> * try again", instead of blocking a process which
> * would rather stay awake. */
> if ((file->f_flags & O_NONBLOCK) && Already_Open) return -EAGAIN;
> /* This is the correct place for MOD_INC_USE_COUNT
> * because if a process is in the loop, which is
> * within the kernel module, the kernel module must
> * not be removed. */
> MOD_INC_USE_COUNT;
> /* If the file is already open, wait until it isn't */
> while (Already_Open) {
>#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,2,0)
> int i, is_sig=0;
>#endif
> /* This function puts the current process,
> * including any system calls, such as us, to sleep.
> * Execution will be resumed right after the function
> * call, either because somebody called
> * wake_up(&WaitQ) (only module_close does that,
> * when the file is closed) or when a signal, such
> * as Ctrl-C, is sent to the process */
> module_interruptible_sleep_on(&WaitQ);
> /* If we woke up because we got a signal we're not
> * blocking, return -EINTR (fail the system call).
> * This allows processes to be killed or stopped. */
> /*
> * Emmanuel Papirakis:
> *
> * This is a little update to work with 2.2.*. Signals
> * now are contained in two words (64 bits) and are
> * stored in a structure that contains an array of two
> * unsigned longs. We now have to make 2 checks in our if.
> *
> * Ori Pomerantz:
> *
> * Nobody promised me they'll never use more than 64
> * bits, or that this book won't be used for a version
> * of Linux with a word size of 16 bits. This code
