一 scullpipe的代码

    1 scull.h

#ifndef _SCULL_H_
#define _SCULL_H_

#include <linux/ioctl.h> /* needed for the _IOW etc stuff used later */

/*
 * Macros to help debugging
 */

#undef PDEBUG             /* undef it, just in case */
#ifdef SCULL_DEBUG
#  ifdef __KERNEL__
     /* This one if debugging is on, and kernel space */
#    define PDEBUG(fmt, args...) printk( KERN_DEBUG "scull: " fmt, ## args)
#  else
     /* This one for user space */
#    define PDEBUG(fmt, args...) fprintf(stderr, fmt, ## args)
#  endif
#else
#  define PDEBUG(fmt, args...) /* not debugging: nothing */
#endif

#undef PDEBUGG
#define PDEBUGG(fmt, args...) /* nothing: it's a placeholder */

#ifndef SCULL_MAJOR
#define SCULL_MAJOR 0   /* dynamic major by default */
#endif

#ifndef SCULL_P_NR_DEVS
#define SCULL_P_NR_DEVS 4  /* scullpipe0 through scullpipe3 */
#endif

/*
 * The pipe device is a simple circular buffer. Here its default size
 */
#ifndef SCULL_P_BUFFER
#define SCULL_P_BUFFER 4000
#endif

/*
 * Representation of scull quantum sets.
 */

/*
 * Split minors in two parts
 */
#define TYPE(minor)	(((minor) >> 4) & 0xf)	/* high nibble */
#define NUM(minor)	((minor) & 0xf)		/* low  nibble */


/*
 * The different configurable parameters
 */
extern int scull_major;     /* main.c */
extern int scull_p_nr_devs;

extern int scull_p_buffer;	/* pipe.c */


/*
 * Prototypes for shared functions
 */

int     scull_p_init(void);
void    scull_p_cleanup(void);

/*
 * Ioctl definitions
 */

/* Use 'k' as magic number */
#define SCULL_IOC_MAGIC  'k'
/* Please use a different 8-bit number in your code */

#define SCULL_P_IOCTSIZE _IO(SCULL_IOC_MAGIC,   0)
#define SCULL_P_IOCQSIZE _IO(SCULL_IOC_MAGIC,   1)
/* ... more to come */

#define SCULL_IOC_MAXNR 1

#endif /* _SCULL_H_ */

2 pipe.c的源码

/*
 * pipe.c -- fifo driver for scull
 *
 * Copyright (C) 2001 Alessandro Rubini and Jonathan Corbet
 * Copyright (C) 2001 O'Reilly & Associates
 *
 * The source code in this file can be freely used, adapted,
 * and redistributed in source or binary form, so long as an
 * acknowledgment appears in derived source files.  The citation
 * should list that the code comes from the book "Linux Device
 * Drivers" by Alessandro Rubini and Jonathan Corbet, published
 * by O'Reilly & Associates.   No warranty is attached;
 * we cannot take responsibility for errors or fitness for use.
 *
 */
 
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/init.h>

#include <linux/kernel.h>	/* printk(), min() */
#include <linux/slab.h>		/* kmalloc() */
#include <linux/fs.h>		/* everything... */
#include <linux/proc_fs.h>
#include <linux/errno.h>	/* error codes */
#include <linux/types.h>	/* size_t */
#include <linux/fcntl.h>
#include <linux/poll.h>
#include <linux/cdev.h>
#include <asm/uaccess.h>

#include "scull.h"		/* local definitions */

int scull_major =   SCULL_MAJOR;
int scull_minor =   0;
int scull_p_nr_devs = SCULL_P_NR_DEVS;	/* number of pipe devices */
int scull_p_buffer =  SCULL_P_BUFFER;	/* buffer size */


module_param(scull_major, int, S_IRUGO);
module_param(scull_minor, int, S_IRUGO);
module_param(scull_p_nr_devs, int, 0);	/* FIXME check perms */
module_param(scull_p_buffer, int, 0);

struct scull_pipe {
        wait_queue_head_t inq, outq;       /* read and write queues */
        char *buffer, *end;                /* begin of buf, end of buf */
        int buffersize;                    /* used in pointer arithmetic */
        char *rp, *wp;                     /* where to read, where to write */
        int nreaders, nwriters;            /* number of openings for r/w */
        struct fasync_struct *async_queue; /* asynchronous readers */