struct fb_fix_screeninfo fix;	struct fb_con2fbmap con2fb;	int i;		if (! fb)		return -ENODEV;
	switch (cmd) {	case FBIOGET_VSCREENINFO:		if ((i = fb->fb_get_var(&var, PROC_CONSOLE(info), info)))			return i;		return copy_to_user((void *) arg, &var,				    sizeof(var)) ? -EFAULT : 0;	case FBIOPUT_VSCREENINFO:		if (copy_from_user(&var, (void *) arg, sizeof(var)))			return -EFAULT;		i = var.activate & FB_ACTIVATE_ALL			    ? set_all_vcs(fbidx, fb, &var, info)			    : fb->fb_set_var(&var, PROC_CONSOLE(info), info);		if (i)			return i;		if (copy_to_user((void *) arg, &var, sizeof(var)))			return -EFAULT;		return 0;	case FBIOGET_FSCREENINFO:		if ((i = fb->fb_get_fix(&fix, PROC_CONSOLE(info), info)))			return i;		return copy_to_user((void *) arg, &fix, sizeof(fix)) ?			-EFAULT : 0;	case FBIOPUTCMAP:		if (copy_from_user(&cmap, (void *) arg, sizeof(cmap)))			return -EFAULT;		return (fb->fb_set_cmap(&cmap, 0, PROC_CONSOLE(info), info));	case FBIOGETCMAP:		if (copy_from_user(&cmap, (void *) arg, sizeof(cmap)))			return -EFAULT;		return (fb->fb_get_cmap(&cmap, 0, PROC_CONSOLE(info), info));	case FBIOPAN_DISPLAY:		if (copy_from_user(&var, (void *) arg, sizeof(var)))			return -EFAULT;		if (fb->fb_pan_display == NULL)			return (var.xoffset || var.yoffset) ? -EINVAL : 0;		if ((i=fb->fb_pan_display(&var, PROC_CONSOLE(info), info)))			return i;		if (copy_to_user((void *) arg, &var, sizeof(var)))			return -EFAULT;		return i;	case FBIOGET_CON2FBMAP:		if (copy_from_user(&con2fb, (void *)arg, sizeof(con2fb)))			return -EFAULT;		if (con2fb.console < 1 || con2fb.console > MAX_NR_CONSOLES)		    return -EINVAL;		con2fb.framebuffer = con2fb_map[con2fb.console-1];		return copy_to_user((void *)arg, &con2fb,				    sizeof(con2fb)) ? -EFAULT : 0;	case FBIOPUT_CON2FBMAP:		if (copy_from_user(&con2fb, (void *)arg, sizeof(con2fb)))			return - EFAULT;		if (con2fb.console < 0 || con2fb.console > MAX_NR_CONSOLES)		    return -EINVAL;		if (con2fb.framebuffer < 0 || con2fb.framebuffer >= FB_MAX)		    return -EINVAL;#ifdef CONFIG_KMOD		if (!registered_fb[con2fb.framebuffer])		    try_to_load(con2fb.framebuffer);#endif /* CONFIG_KMOD */		if (!registered_fb[con2fb.framebuffer])		    return -EINVAL;		if (con2fb.console != 0)		    set_con2fb_map(con2fb.console-1, con2fb.framebuffer);		else		    /* set them all */		    for (i = 0; i < MAX_NR_CONSOLES; i++)			set_con2fb_map(i, con2fb.framebuffer);		return 0;	case FBIOBLANK:		if (info->blank == 0)			return -EINVAL;		(*info->blank)(arg, info);		return 0;	default:		if (fb->fb_ioctl == NULL)			return -EINVAL;		return fb->fb_ioctl(inode, file, cmd, arg, PROC_CONSOLE(info),				    info);	}}static int fb_mmap(struct file *file, struct vm_area_struct * vma){	int fbidx = GET_FB_IDX(file->f_dentry->d_inode->i_rdev);	struct fb_info *info = registered_fb[fbidx];	struct fb_ops *fb = info->fbops;	unsigned long off;#if !defined(__sparc__) || defined(__sparc_v9__)	struct fb_fix_screeninfo fix;	struct fb_var_screeninfo var;	unsigned long start;	u32 len;#endif	if (vma->vm_pgoff > (~0UL >> PAGE_SHIFT))		return -EINVAL;	off = vma->vm_pgoff << PAGE_SHIFT;	if (!fb)		return -ENODEV;	if (fb->fb_mmap) {		int res;		lock_kernel();		res = fb->fb_mmap(info, file, vma);		unlock_kernel();		/* This is an IO map - tell maydump to skip this VMA */		vma->vm_flags |= VM_IO;		return res;	}#if defined(__sparc__) && !defined(__sparc_v9__)	/* Should never get here, all fb drivers should have their own	   mmap routines */	return -EINVAL;#else	/* !sparc32... */	lock_kernel();	fb->fb_get_fix(&fix, PROC_CONSOLE(info), info);	/* frame buffer memory */	start = fix.smem_start;	len = PAGE_ALIGN((start & ~PAGE_MASK)+fix.smem_len);	if (off >= len) {		/* memory mapped io */		off -= len;		fb->fb_get_var(&var, PROC_CONSOLE(info), info);		if (var.accel_flags) {			unlock_kernel();			return -EINVAL;		}		start = fix.mmio_start;		len = PAGE_ALIGN((start & ~PAGE_MASK)+fix.mmio_len);	}	unlock_kernel();	start &= PAGE_MASK;	if ((vma->vm_end - vma->vm_start + off) > len)		return -EINVAL;	off += start;	vma->vm_pgoff = off >> PAGE_SHIFT;	/* This is an IO map - tell maydump to skip this VMA */	vma->vm_flags |= VM_IO;#if defined(__sparc_v9__)	vma->vm_flags |= (VM_SHM | VM_LOCKED);	if (io_remap_page_range(vma, vma->vm_start, off,				vma->vm_end - vma->vm_start, vma->vm_page_prot, 0))		return -EAGAIN;#else#if defined(__mc68000__)#if defined(CONFIG_SUN3)	pgprot_val(vma->vm_page_prot) |= SUN3_PAGE_NOCACHE;#else	if (CPU_IS_020_OR_030)		pgprot_val(vma->vm_page_prot) |= _PAGE_NOCACHE030;	if (CPU_IS_040_OR_060) {		pgprot_val(vma->vm_page_prot) &= _CACHEMASK040;		/* Use no-cache mode, serialized */		pgprot_val(vma->vm_page_prot) |= _PAGE_NOCACHE_S;	}#endif#elif defined(__powerpc__)	pgprot_val(vma->vm_page_prot) |= _PAGE_NO_CACHE|_PAGE_GUARDED;#elif defined(__alpha__)	/* Caching is off in the I/O space quadrant by design.  */#elif defined(__i386__) || defined(__x86_64__)	if (boot_cpu_data.x86 > 3)		pgprot_val(vma->vm_page_prot) |= _PAGE_PCD;#elif defined(__arm__) || defined(__mips__)	vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);#elif defined(__sh__)	pgprot_val(vma->vm_page_prot) &= ~_PAGE_CACHABLE;#elif defined(__hppa__)	pgprot_val(vma->vm_page_prot) |= _PAGE_NO_CACHE; #elif defined(__ia64__)	vma->vm_page_prot = pgprot_writecombine(vma->vm_page_prot);#elif defined(__hppa__)	pgprot_val(vma->vm_page_prot) |= _PAGE_NO_CACHE; #else#warning What do we have to do here??#endif	if (io_remap_page_range(vma, vma->vm_start, off,			     vma->vm_end - vma->vm_start, vma->vm_page_prot))		return -EAGAIN;#endif /* !__sparc_v9__ */	return 0;#endif /* !sparc32 */}#if 1 /* to go away in 2.5.0 */int GET_FB_IDX(kdev_t rdev){    int fbidx = MINOR(rdev);    if (fbidx >= 32) {	int newfbidx = fbidx >> 5;	static int warned;	if (!(warned & (1<<newfbidx))) {	    warned |= 1<<newfbidx;	    printk("Warning: Remapping obsolete /dev/fb* minor %d to %d\n",		   fbidx, newfbidx);	}	fbidx = newfbidx;    }    return fbidx;}#endifstatic intfb_open(struct inode *inode, struct file *file){	int fbidx = GET_FB_IDX(inode->i_rdev);	struct fb_info *info;	int res = 0;#ifdef CONFIG_KMOD	if (!(info = registered_fb[fbidx]))		try_to_load(fbidx);#endif /* CONFIG_KMOD */	if (!(info = registered_fb[fbidx]))		return -ENODEV;	if (info->fbops->owner)		__MOD_INC_USE_COUNT(info->fbops->owner);	if (info->fbops->fb_open) {		res = info->fbops->fb_open(info,1);		if (res && info->fbops->owner)			__MOD_DEC_USE_COUNT(info->fbops->owner);	}	return res;}static int fb_release(struct inode *inode, struct file *file){	int fbidx = GET_FB_IDX(inode->i_rdev);	struct fb_info *info;	lock_kernel();	info = registered_fb[fbidx];	if (info->fbops->fb_release)		info->fbops->fb_release(info,1);	if (info->fbops->owner)		__MOD_DEC_USE_COUNT(info->fbops->owner);	unlock_kernel();	return 0;}static struct file_operations fb_fops = {	owner:		THIS_MODULE,	read:		fb_read,	write:		fb_write,	ioctl:		fb_ioctl,	mmap:		fb_mmap,	open:		fb_open,	release:	fb_release,#ifdef HAVE_ARCH_FB_UNMAPPED_AREA	get_unmapped_area: get_fb_unmapped_area,#endif};static devfs_handle_t devfs_handle;/** *	register_framebuffer - registers a frame buffer device *	@fb_info: frame buffer info structure * *	Registers a frame buffer device @fb_info. * *	Returns negative errno on error, or zero for success. * */intregister_framebuffer(struct fb_info *fb_info){	int i, j;	char name_buf[8];	static int fb_ever_opened[FB_MAX];	static int first = 1;	//若登記的設備已達到最大數目，返回
	if (num_registered_fb == FB_MAX)		return -ENXIO;	num_registered_fb++;

	//查找登記表中未使用的位置，作為該設備的登記位置	for (i = 0 ; i < FB_MAX; i++)		if (!registered_fb[i])			break;
	//分配次設備號	fb_info->node = MKDEV(FB_MAJOR, i);
	//注冊該設備	registered_fb[i] = fb_info;
	//設備未打開	if (!fb_ever_opened[i]) {		struct module *owner = fb_info->fbops->owner;		/*		 *  We assume initial frame buffer devices can be opened this		 *  many times		 */		for (j = 0; j < MAX_NR_CONSOLES; j++)			if (con2fb_map[j] == i) {				if (owner)					__MOD_INC_USE_COUNT(owner);				if (!fb_info->fbops->fb_open)					continue;				if (!fb_info->fbops->fb_open(fb_info,0))					continue;				if (owner)					__MOD_DEC_USE_COUNT(owner);			}		fb_ever_opened[i] = 1;//設置設備為打開狀態	}	if (first) {		first = 0;		take_over_console(&fb_con, first_fb_vc, last_fb_vc, fbcon_is_default);	}	sprintf (name_buf, "%d", i);	fb_info->devfs_handle =	    devfs_register (devfs_handle, name_buf, DEVFS_FL_DEFAULT,			    FB_MAJOR, i, S_IFCHR | S_IRUGO | S_IWUGO,			    &fb_fops, NULL);	return 0;}/** *	unregister_framebuffer - releases a frame buffer device *	@fb_info: frame buffer info structure * *	Unregisters a frame buffer device @fb_info. * *	Returns negative errno on error, or zero for success. * */intunregister_framebuffer(struct fb_info *fb_info){	int i, j;	i = GET_FB_IDX(fb_info->node);//獲取對應的設備號	//查詢設備是否空閑
	for (j = 0; j < MAX_NR_CONSOLES; j++)		if (con2fb_map[j] == i)			return -EBUSY;
	//若設備未登記，返回	if (!registered_fb[i])		return -EINVAL;
	devfs_unregister (fb_info->devfs_handle);	fb_info->devfs_handle = NULL;	devfs_unregister (fb_info->devfs_lhandle);	fb_info->devfs_lhandle = NULL;
	//將該設備從FB登記表中清除	registered_fb[i]=NULL;	num_registered_fb--;	return 0;}/** *	fbmem_init - init frame buffer subsystem * *	Initialize the frame buffer subsystem. * *	NOTE: This function is _only_ to be called by drivers/char/mem.c. * */void __init fbmem_init(void){	int i;	create_proc_read_entry("fb", 0, 0, fbmem_read_proc, NULL);	devfs_handle = devfs_mk_dir (NULL, "fb", NULL);	if (devfs_register_chrdev(FB_MAJOR,"fb",&fb_fops))		printk("unable to get major %d for fb devs\n", FB_MAJOR);#ifdef CONFIG_FB_OF	if (ofonly) {		offb_init();		return;	}#endif	/*	 *  Probe for all builtin frame buffer devices	 */	for (i = 0; i < num_pref_init_funcs; i++)		pref_init_funcs[i]();	for (i = 0; i < NUM_FB_DRIVERS; i++)		if (fb_drivers[i].init)			fb_drivers[i].init();}/** *	video_setup - process command line options *	@options: string of options * *	Process command line options for frame buffer subsystem. * *	NOTE: This function is a __setup and __init function. * *	Returns zero. * */int __init video_setup(char *options){    int i, j;    if (!options || !*options)	    return 0;	        if (!strncmp(options, "scrollback:", 11)) {	    options += 11;	    if (*options) {		fbcon_softback_size = simple_strtoul(options, &options, 0);		if (*options == 'k' || *options == 'K') {			fbcon_softback_size *= 1024;			options++;		}		if (*options != ',')			return 0;		options++;	    } else	        return 0;    }    if (!strncmp(options, "map:", 4)) {	    options += 4;	    if (*options)		    for (i = 0, j = 0; i < MAX_NR_CONSOLES; i++) {			    if (!options[j])				    j = 0;			    con2fb_map[i] = (options[j++]-'0') % FB_MAX;		    }	    return 0;    }        if (!strncmp(options, "vc:", 3)) {	    options += 3;	    if (*options)		first_fb_vc = simple_strtoul(options, &options, 10) - 1;	    if (first_fb_vc < 0)		first_fb_vc = 0;	    if (*options++ == '-')		last_fb_vc = simple_strtoul(options, &options, 10) - 1;	    fbcon_is_default = 0;    }#ifdef CONFIG_FB_OF    if (!strcmp(options, "ofonly")) {	    ofonly = 1;	    return 0;    }#endif    if (num_pref_init_funcs == FB_MAX)	    return 0;    for (i = 0; i < NUM_FB_DRIVERS; i++) {	    j = strlen(fb_drivers[i].name);	    if (!strncmp(options, fb_drivers[i].name, j) &&		options[j] == ':') {		    if (!strcmp(options+j+1, "off"))			    fb_drivers[i].init = NULL;		    else {			    if (fb_drivers[i].init) {				    pref_init_funcs[num_pref_init_funcs++] =					    fb_drivers[i].init;				    fb_drivers[i].init = NULL;			    }			    if (fb_drivers[i].setup)				    fb_drivers[i].setup(options+j+1);		    }		    return 0;	    }    }    /*     * If we get here no fb was specified.     * We consider the argument to be a global video mode option.     */    global_mode_option = options;    return 0;}__setup("video=", video_setup);    /*     *  Visible symbols for modules     */EXPORT_SYMBOL(register_framebuffer);EXPORT_SYMBOL(unregister_framebuffer);EXPORT_SYMBOL(registered_fb);EXPORT_SYMBOL(num_registered_fb);#if 1 /* to go away in 2.5.0 */EXPORT_SYMBOL(GET_FB_IDX);#endifMODULE_LICENSE("GPL");