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：[email protected] ----------------------------------------------------------------------- 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13 if (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_handler input_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handler joydev.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connect static 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id return 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sysfs if (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); else list_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_EVENT 0 #define INPUT_PASS_TO_HANDLERS 1 #define INPUT_PASS_TO_DEVICE 2 #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handler break; } 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 else input_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handle if (!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_event static 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); else list_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handler if (handler) new_fops = fops_get(handler->fops); //得到handler中的fops mutex_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fops file->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open if (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。