LDD之input子系统--代码分析

-----------------------------------------------------------------------本文系本站原创,欢迎转载!转载请注明出处:http://blog.csdn.net/android_huber交流邮箱：[e-mail]-----------------------------------------------------------------------                                                   input子系统 ---  代码分析                                                       input初始化分析static int __init input_init(void){int err;input_init_abs_bypass();err = class_register(&input_class); //注册一个input的类，所有的input设备都是这个类if (err) {printk(KERN_ERR "input: unable to register input_dev class\n");return err;}err = input_proc_init();if (err)goto fail1;err = register_chrdev(INPUT_MAJOR, "input", &input_fops); 注册字符设备，input设备主设备号为13if (err) {printk(KERN_ERR "input: unable to register char major %d", INPUT_MAJOR);goto fail2;}return 0; fail2:input_proc_exit(); fail1:class_unregister(&input_class);return err;}static const struct file_operations input_fops = {.owner = THIS_MODULE,.open = input_open_file,};int input_register_device(struct input_dev *dev){static atomic_t input_no = ATOMIC_INIT(0);struct input_handler *handler;const char *path;int error;/* Every input device generates EV_SYN/SYN_REPORT events. */__set_bit(EV_SYN, dev->evbit); //设置支持的事件/* KEY_RESERVED is not supposed to be transmitted to userspace. */__clear_bit(KEY_RESERVED, dev->keybit);/* Make sure that bitmasks not mentioned in dev->evbit are clean. */input_cleanse_bitmasks(dev);/* * If delay and period are pre-set by the driver, then autorepeating * is handled by the driver itself and we don't do it in input.c. */init_timer(&dev->timer); //初始化定时器if (!dev->rep[REP_DELAY] && !dev->rep[REP_PERIOD]) {dev->timer.data = (long) dev;dev->timer.function = input_repeat_key;dev->rep[REP_DELAY] = 250;dev->rep[REP_PERIOD] = 33;}if (!dev->getkeycode)dev->getkeycode = input_default_getkeycode;if (!dev->setkeycode)dev->setkeycode = input_default_setkeycode;dev_set_name(&dev->dev, "input%ld",     (unsigned long) atomic_inc_return(&input_no) - 1);error = device_add(&dev->dev); //添加设备进总线if (error)return error;path = kobject_get_path(&dev->dev.kobj, GFP_KERNEL); //创建sys目录printk(KERN_INFO "input: %s as %s\n",dev->name ? dev->name : "Unspecified device", path ? path : "N/A");kfree(path);error = mutex_lock_interruptible(&input_mutex);if (error) {device_del(&dev->dev);return error;}list_add_tail(&dev->node, &input_dev_list); //将该设备加入到input设备链表中list_for_each_entry(handler, &input_handler_list, node) input_attach_handler(dev, handler);对每一个挂在input_handler_list的handler调用input_attach_handlerinput_wakeup_procfs_readers();input_handler_list链表是在input_register_handler中填充，input_dev_list是在input_register_device中填充添加。mutex_unlock(&input_mutex);return 0;}static void input_repeat_key(unsigned long data){struct input_dev *dev = (void *) data;unsigned long flags;spin_lock_irqsave(&dev->event_lock, flags);if (test_bit(dev->repeat_key, dev->key) &&    is_event_supported(dev->repeat_key, dev->keybit, KEY_MAX)) {input_pass_event(dev, EV_KEY, dev->repeat_key, 2);if (dev->sync) { //如果更新标志位设置了，上报更新/* * Only send SYN_REPORT if we are not in a middle * of driver parsing a new hardware packet. * Otherwise assume that the driver will send * SYN_REPORT once it's done. */input_pass_event(dev, EV_SYN, SYN_REPORT, 1);}if (dev->rep[REP_PERIOD])mod_timer(&dev->timer, jiffies +msecs_to_jiffies(dev->rep[REP_PERIOD]));}spin_unlock_irqrestore(&dev->event_lock, flags);}int input_register_handler(struct input_handler *handler){struct input_dev *dev;int retval;retval = mutex_lock_interruptible(&input_mutex);if (retval)return retval;INIT_LIST_HEAD(&handler->h_list);if (handler->fops != NULL) {if (input_table[handler->minor >> 5]) {retval = -EBUSY;goto out;}input_table[handler->minor >> 5] = handler; //除以32,每32个次设备号对应一个handler，evdev为64～64-1}list_add_tail(&handler->node, &input_handler_list); //添加handler到input_handler_list链表中list_for_each_entry(dev, &input_dev_list, node)input_attach_handler(dev, handler);对每一个挂在input_dev_list链表中的dev调用input_attach_handler.input_wakeup_procfs_readers(); out:mutex_unlock(&input_mutex);return retval;}在evbug.c，evdev.c，joydev.c，mousedev.c中分别调用了一次input_register_handler，注册对应属性的handlerjoydev.c ------Joystick device driver---- 游戏手柄/操纵杆支持mousedev.c -------ExplorerPS/2 device driver------鼠标支持evdev.c------Event char devices, giving access to raw input device events.---原始输入设备支持在这里只分析evdev.c，因为一般都是evdev设备static int input_attach_handler(struct input_dev *dev, struct input_handler *handler){const struct input_device_id *id;int error;id = input_match_device(handler, dev); //主要调用了handler的match函数if (!id)return -ENODEV;error = handler->connect(handler, dev, id); //handler的connect函数if (error && error != -ENODEV)printk(KERN_ERR"input: failed to attach handler %s to device %s, ""error: %d\n",handler->name, kobject_name(&dev->dev.kobj), error);return error;}从上面程序中可以知道，attach的过程就是调用handler的match函数，match通过，进行connectstatic const struct input_device_id *input_match_device(struct input_handler *handler,struct input_dev *dev){const struct input_device_id *id;int i;for (id = handler->id_table; id->flags || id->driver_info; id++) {if (id->flags & INPUT_DEVICE_ID_MATCH_BUS)if (id->bustype != dev->id.bustype)continue;if (id->flags & INPUT_DEVICE_ID_MATCH_VENDOR)if (id->vendor != dev->id.vendor)continue;if (id->flags & INPUT_DEVICE_ID_MATCH_PRODUCT)if (id->product != dev->id.product)continue;if (id->flags & INPUT_DEVICE_ID_MATCH_VERSION)if (id->version != dev->id.version)continue;MATCH_BIT(evbit,  EV_MAX);MATCH_BIT(keybit, KEY_MAX);MATCH_BIT(relbit, REL_MAX);MATCH_BIT(absbit, ABS_MAX);MATCH_BIT(mscbit, MSC_MAX);MATCH_BIT(ledbit, LED_MAX);MATCH_BIT(sndbit, SND_MAX);MATCH_BIT(ffbit,  FF_MAX);MATCH_BIT(swbit,  SW_MAX);if (!handler->match || handler->match(handler, dev)) //调用handler的match,如果未定义match则直接返回idreturn id;}return NULL;}                                                            evdev分析static int __init evdev_init(void){return input_register_handler(&evdev_handler);}static struct input_handler evdev_handler = {.event= evdev_event,.connect= evdev_connect,.disconnect= evdev_disconnect,.fops= &evdev_fops,.minor= EVDEV_MINOR_BASE,.name= "evdev",.id_table= evdev_ids,};static int evdev_connect(struct input_handler *handler, struct input_dev *dev, const struct input_device_id *id){struct evdev *evdev;int minor;int error;for (minor = 0; minor < EVDEV_MINORS; minor++)if (!evdev_table[minor])break;if (minor == EVDEV_MINORS) {printk(KERN_ERR "evdev: no more free evdev devices\n");return -ENFILE;}evdev = kzalloc(sizeof(struct evdev), GFP_KERNEL);if (!evdev)return -ENOMEM;INIT_LIST_HEAD(&evdev->client_list);spin_lock_init(&evdev->client_lock);mutex_init(&evdev->mutex);init_waitqueue_head(&evdev->wait);dev_set_name(&evdev->dev, "event%d", minor);evdev->exist = 1;evdev->minor = minor;evdev->handle.dev = input_get_device(dev);evdev->handle.name = dev_name(&evdev->dev);evdev->handle.handler = handler;evdev->handle.private = evdev;这个结构封装了一个handle结构，这个结构与handler不同，handle可以看成是handler和input device的结合。evdev->dev.devt = MKDEV(INPUT_MAJOR, EVDEV_MINOR_BASE + minor);evdev->dev.class = &input_class;evdev->dev.parent = &dev->dev;evdev->dev.release = evdev_free;device_initialize(&evdev->dev);在这段代码里主要完成evdev封装的device的初始化.注意在这里,使它所属的类指向input_class.这样在/sysfs中创建的设备目录就会在/sys/class/input/下面显示.error = input_register_handle(&evdev->handle);if (error)goto err_free_evdev;error = evdev_install_chrdev(evdev);if (error)goto err_unregister_handle;error = device_add(&evdev->dev); //将evdev->device注册到sysfsif (error)goto err_cleanup_evdev;return 0; err_cleanup_evdev:evdev_cleanup(evdev); err_unregister_handle:input_unregister_handle(&evdev->handle); err_free_evdev:put_device(&evdev->dev);return error;}int input_register_handle(struct input_handle *handle){struct input_handler *handler = handle->handler;struct input_dev *dev = handle->dev;int error;/* * We take dev->mutex here to prevent race with * input_release_device(). */error = mutex_lock_interruptible(&dev->mutex);if (error)return error;//将handle挂载到h_list结构体if (handler->filter)list_add_rcu(&handle->d_node, &dev->h_list);elselist_add_tail_rcu(&handle->d_node, &dev->h_list);mutex_unlock(&dev->mutex);//还将handle挂载在handler的h_list结构体list_add_tail_rcu(&handle->h_node, &handler->h_list);//如果handler定义了start，则调用start，这里没有定义if (handler->start)handler->start(handle);return 0;}static int evdev_install_chrdev(struct evdev *evdev){evdev_table[evdev->minor] = evdev; //evdev_table的minor项指向evdev.return 0;}                                                       event层分析static inline void input_report_abs(struct input_dev *dev, unsigned int code, int value){input_event(dev, EV_ABS, code, value);}static inline void input_report_key(struct input_dev *dev, unsigned int code, int value){input_event(dev, EV_KEY, code, !!value);}static inline void input_sync(struct input_dev *dev){input_event(dev, EV_SYN, SYN_REPORT, 0);}static inline void input_mt_sync(struct input_dev *dev){input_event(dev, EV_SYN, SYN_MT_REPORT, 0);}void input_event(struct input_dev *dev, unsigned int type, unsigned int code, int value){unsigned long flags;if (is_event_supported(type, dev->evbit, EV_MAX)) {spin_lock_irqsave(&dev->event_lock, flags);add_input_randomness(type, code, value);input_handle_event(dev, type, code, value);spin_unlock_irqrestore(&dev->event_lock, flags);}}#define INPUT_IGNORE_EVENT0#define INPUT_PASS_TO_HANDLERS1#define INPUT_PASS_TO_DEVICE2#define INPUT_PASS_TO_ALL(INPUT_PASS_TO_HANDLERS | INPUT_PASS_TO_DEVICE)static void input_handle_event(struct input_dev *dev,       unsigned int type, unsigned int code, int value){int disposition = INPUT_IGNORE_EVENT;switch (type) {case EV_SYN:switch (code) {case SYN_CONFIG:disposition = INPUT_PASS_TO_ALL;break;case SYN_REPORT:if (!dev->sync) {dev->sync = 1; //更新disposition = INPUT_PASS_TO_HANDLERS; //控制权交给handler}break;case SYN_MT_REPORT:dev->sync = 0; //等待更新disposition = INPUT_PASS_TO_HANDLERS; //控制权交给handlerbreak;}break;case EV_KEY:if (is_event_supported(code, dev->keybit, KEY_MAX) && //判断事件是否有效    !!test_bit(code, dev->key) != value) {if (value != 2) {__change_bit(code, dev->key);if (value)input_start_autorepeat(dev, code); //如果有按键按下,则循环elseinput_stop_autorepeat(dev);}disposition = INPUT_PASS_TO_HANDLERS;}break;case EV_SW:if (is_event_supported(code, dev->swbit, SW_MAX) &&    !!test_bit(code, dev->sw) != value) {__change_bit(code, dev->sw);disposition = INPUT_PASS_TO_HANDLERS;}break;case EV_ABS:if (is_event_supported(code, dev->absbit, ABS_MAX)) {if (test_bit(code, input_abs_bypass)) {disposition = INPUT_PASS_TO_HANDLERS;break;}value = input_defuzz_abs_event(value,dev->abs[code], dev->absfuzz[code]); //处理坐标，什么原理啊？？if (dev->abs[code] != value) {dev->abs[code] = value; //保存value到dev->abs[code]disposition = INPUT_PASS_TO_HANDLERS;}}break;case EV_REL:if (is_event_supported(code, dev->relbit, REL_MAX) && value)disposition = INPUT_PASS_TO_HANDLERS;break;case EV_MSC:if (is_event_supported(code, dev->mscbit, MSC_MAX))disposition = INPUT_PASS_TO_ALL;break;case EV_LED:if (is_event_supported(code, dev->ledbit, LED_MAX) &&    !!test_bit(code, dev->led) != value) {__change_bit(code, dev->led);disposition = INPUT_PASS_TO_ALL;}break;case EV_SND:if (is_event_supported(code, dev->sndbit, SND_MAX)) {if (!!test_bit(code, dev->snd) != !!value)__change_bit(code, dev->snd);disposition = INPUT_PASS_TO_ALL;}break;case EV_REP:if (code <= REP_MAX && value >= 0 && dev->rep[code] != value) {dev->rep[code] = value;disposition = INPUT_PASS_TO_ALL;}break;case EV_FF:if (value >= 0)disposition = INPUT_PASS_TO_ALL;break;case EV_PWR:disposition = INPUT_PASS_TO_ALL;break;}if (disposition != INPUT_IGNORE_EVENT && type != EV_SYN)dev->sync = 0;if ((disposition & INPUT_PASS_TO_DEVICE) && dev->event) //调用device的event函数,如果定义了dev->event的话dev->event(dev, type, code, value);if (disposition & INPUT_PASS_TO_HANDLERS) //调用handler的event函数input_pass_event(dev, type, code, value);}static int input_defuzz_abs_event(int value, int old_val, int fuzz){    什么原理啊？？？if (fuzz) {if (value > old_val - fuzz / 2 && value < old_val + fuzz / 2)return old_val;if (value > old_val - fuzz && value < old_val + fuzz)return (old_val * 3 + value) / 4;if (value > old_val - fuzz * 2 && value < old_val + fuzz * 2)return (old_val + value) / 2;}return value;}static void input_pass_event(struct input_dev *dev,     unsigned int type, unsigned int code, int value){struct input_handler *handler;struct input_handle *handle;rcu_read_lock();handle = rcu_dereference(dev->grab);if (handle)handle->handler->event(handle, type, code, value); //evdev的event函数else {bool filtered = false;list_for_each_entry_rcu(handle, &dev->h_list, d_node) {if (!handle->open)continue;handler = handle->handler; //找到handleif (!handler->filter) {if (filtered)break;handler->event(handle, type, code, value);} else if (handler->filter(handle, type, code, value))filtered = true;}}rcu_read_unlock();}evdev中还有一个比较重要的函数是evdev_eventstatic void evdev_event(struct input_handle *handle,unsigned int type, unsigned int code, int value){struct evdev *evdev = handle->private;struct evdev_client *client;struct input_event event; //input_event结构体,即为上层上报的事件struct input_event {struct timeval time; //事件上报事件__u16 type;//事件类型码,如EV_ABS/EV_KEY/EV_REL/EV_SYN__u16 code;//按键时为扫描码,触摸屏时为数据类型__s32 value;//属性值,按键时代表按下弹起,触摸屏为数据};struct timespec ts;ktime_get_ts(&ts);event.time.tv_sec = ts.tv_sec; //填充时间,秒event.time.tv_usec = ts.tv_nsec / NSEC_PER_USEC; //纳秒event.type = type; //填充类型码event.code = code; //填充按键扫描码或touch数据类型event.value = value; //填充数据类型值rcu_read_lock();client = rcu_dereference(evdev->grab);if (client)evdev_pass_event(client, &event);elselist_for_each_entry_rcu(client, &evdev->client_list, node)evdev_pass_event(client, &event);rcu_read_unlock();wake_up_interruptible(&evdev->wait); //唤醒睡眠在evdev->wait等待队列等待输入信息的进程,通知evdev_read读取。}static void evdev_pass_event(struct evdev_client *client,     struct input_event *event){/* * Interrupts are disabled, just acquire the lock */spin_lock(&client->buffer_lock);client->buffer[client->head++] = *event; //加入client的信息缓冲client->head &= EVDEV_BUFFER_SIZE - 1; //环形缓存区处理spin_unlock(&client->buffer_lock);if (event->type == EV_SYN)kill_fasync(&client->fasync, SIGIO, POLL_IN); //发送SIGIO信号,告知事件}//将event保存到client->buf中，client->head是当前数据的位置。注意这里是一个环形缓存区.写数据是从client->head写.而读数据则是从client->tail中读.                                                           信息读取//设备的open函数static int input_open_file(struct inode *inode, struct file *file){struct input_handler *handler;const struct file_operations *old_fops, *new_fops = NULL;int err;err = mutex_lock_interruptible(&input_mutex);if (err)return err;/* No load-on-demand here? */handler = input_table[iminor(inode) >> 5]; //根据次设备号来得到handler，次设备号右移5位,这个就是input子系统次设备号的分配了，evdev的次设备号是64～64+32-1，对应着同一个handlerif (handler)new_fops = fops_get(handler->fops); //得到handler中的fopsmutex_unlock(&input_mutex);/* * That's _really_ odd. Usually NULL ->open means "nothing special", * not "no device". Oh, well... */if (!new_fops || !new_fops->open) {fops_put(new_fops);err = -ENODEV;goto out;}old_fops = file->f_op; //保存老的fopsfile->f_op = new_fops; //然后将handler中的fops替换掉当前的fops.这样只要设备open以后，调用其它的函数时(如read,write,poll,ioctl就可以调用)err = new_fops->open(inode, file); //调用handler的fops中的openif (err) {fops_put(file->f_op);file->f_op = fops_get(old_fops);}fops_put(old_fops);out:return err;}//event层中的read函数static ssize_t evdev_read(struct file *file, char __user *buffer,  size_t count, loff_t *ppos){struct evdev_client *client = file->private_data;struct evdev *evdev = client->evdev;struct input_event event;int retval;if (count < input_event_size())return -EINVAL;if (client->head == client->tail && evdev->exist && //缓存中没有数据,且设备存在    (file->f_flags & O_NONBLOCK))return -EAGAIN;retval = wait_event_interruptible(evdev->wait,client->head != client->tail || !evdev->exist); //等待evdev_event函数去唤醒if (retval)return retval;if (!evdev->exist)return -ENODEV;while (retval + input_event_size() <= count &&       evdev_fetch_next_event(client, &event)) { //下面开始读取数据if (input_event_to_user(buffer + retval, &event)) //将event结构copy_to_user，给用户层return -EFAULT;retval += input_event_size();}return retval;}static int evdev_fetch_next_event(struct evdev_client *client,  struct input_event *event){int have_event;spin_lock_irq(&client->buffer_lock);have_event = client->head != client->tail;if (have_event) {*event = client->buffer[client->tail++];client->tail &= EVDEV_BUFFER_SIZE - 1;}spin_unlock_irq(&client->buffer_lock);return have_event;}int input_event_to_user(char __user *buffer,const struct input_event *event){if (copy_to_user(buffer, event, sizeof(struct input_event)))return -EFAULT;return 0;}

这篇文章只是分析了一下input子系统的代码，可能看了这么多代码后大家的心里对input的整个框架并不了解，我将在稍后的一篇文章中，放入我刚画好的一张input子系统框架流程图,同时还有对input子系统的一些简单总结，到时大家可以参照一下，会对理解整个input子系统会有帮助。

 结合下一篇带流程图的文章一起看。

http://blog.csdn.net/android_huber/article/details/7407217

图比较大，看不全保存在本地方便放大看。