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这节结合even handler来分析设备的注册和打开的过程，在设备注册之前，必须先初始化INPUT子系统，由input_init()函数来完成static int __init input_init(void){int err;input_init_abs_bypass();err = class_register(&input_class);//注册input类if (err) {printk(KERN_ERR "input: unable to register input_dev class\n");return err;}err = input_proc_init();//创建/proc中的项if (err)goto fail1;/*注册设备，设备号为INPUT_MAJOR(13),后面注册的输入设备都使用该主设备号*/err = register_chrdev(INPUT_MAJOR, "input", &input_fops);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;}input_fops中只定义了open函数。static const struct file_operations input_fops = {.owner = THIS_MODULE,.open = input_open_file,};我们需要在设备驱动层中完成输入设备的注册，通过调用input_register_device()函数来完成，该函数的一个重要任务就是完成设备与事件驱动的匹配。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;__set_bit(EV_SYN, dev->evbit);/* * 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);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;}/*没有定义设备的getkeycode函数，则使用默认的获取键值函数*/if (!dev->getkeycode)dev->getkeycode = input_default_getkeycode;/*没有定义设备的setkeycode函数，则使用默认的设定键值函数*/if (!dev->setkeycode)dev->setkeycode = input_default_setkeycode;/*设定dev的名字*/dev_set_name(&dev->dev, "input%ld", (unsigned long) atomic_inc_return(&input_no) - 1);/*添加设备*/error = device_add(&dev->dev);if (error)return error;path = kobject_get_path(&dev->dev.kobj, GFP_KERNEL);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;}/*将设备添加到input_dev_list设备链表*/list_add_tail(&dev->node, &input_dev_list);/*遍历input_handler_list，试图与每一个handler进行匹配*/list_for_each_entry(handler, &input_handler_list, node)input_attach_handler(dev, handler);input_wakeup_procfs_readers();mutex_unlock(&input_mutex);return 0;}static int input_attach_handler(struct input_dev *dev, struct input_handler *handler){const struct input_device_id *id;int error;/*如果定义了handler的黑名单，并且设备和黑名单中的id匹配了，则该设备不能和handler匹配*/if (handler->blacklist && input_match_device(handler->blacklist, dev))return -ENODEV;id = input_match_device(handler->id_table, dev);if (!id)return -ENODEV;/*执行handler的connect,建立handler与设备之间的联系*/error = handler->connect(handler, dev, id);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;}匹配的具体过程：static const struct input_device_id *input_match_device(const struct input_device_id *id,struct input_dev *dev){int i;/*遍历handler的id_table与device进行匹配*/for (; id->flags || id->driver_info; id++) {/*根据flags的标志位，按需要匹配相应的字段*/if (id->flags & INPUT_DEVICE_ID_MATCH_BUS)if (id->bustype != dev->id.bustype)//总线类型不匹配continue;if (id->flags & INPUT_DEVICE_ID_MATCH_VENDOR)//生产厂商不匹配if (id->vendor != dev->id.vendor)continue;if (id->flags & INPUT_DEVICE_ID_MATCH_PRODUCT)//产品不匹配if (id->product != dev->id.product)continue;if (id->flags & INPUT_DEVICE_ID_MATCH_VERSION)//版本不匹配if (id->version != dev->id.version)continue;MATCH_BIT(evbit, EV_MAX);//匹配所有的事件类型/*匹配所有事件的子事件*/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);return id;//匹配成功，返回id}return NULL;}MATCH_BIT是将device的相应字段和handler的相应字段逐位对比，都一样的话表示成功，否则continue#define MATCH_BIT(bit, max) \for (i = 0; i < BITS_TO_LONGS(max); i++) \if ((id->bit[i] & dev->bit[i]) != id->bit[i]) \break; \if (i != BITS_TO_LONGS(max)) \continue;以event handler为例，看connect函数做了什么：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;/*在evdev_table中找到空闲块，其对应的数组下标再加上EVDEV_MINOR_BASE(64)就是次设备号 每个handler都拥有32个此设备号，也就是最多可以对应32个设备*/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);/*初始化evdev的内部变量*/snprintf(evdev->name, sizeof(evdev->name), "event%d", minor);evdev->exist = 1;evdev->minor = minor;/*初始化handle,每个evdev中都有一个handle*/evdev->handle.dev = input_get_device(dev);evdev->handle.name = evdev->name;evdev->handle.handler = handler;evdev->handle.private = evdev;/*初始化evdev中的内嵌device*/dev_set_name(&evdev->dev, evdev->name);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);/*注册handle,主要将handle链接到input_dev和handler的h_list链表中去*/error = input_register_handle(&evdev->handle);if (error)goto err_free_evdev;/*将evdev存入evdev_table数组*/error = evdev_install_chrdev(evdev);if (error)goto err_unregister_handle;error = device_add(&evdev->dev);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;}至此设备的注册完成！对应event handler,在/dev中将多出一个event(x)设备文件，对应一个evdev实例，应用程序打开它的话也就意味着通过event handler来和设备驱动层传递事件。再来看打开设备的过程，还是以event handler为例，假如打开一个event(x),则先执行：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;lock_kernel();/* No load-on-demand here? *//*32个设备是共用一个handler的,通过此设备号得到设备对应的handler*/handler = input_table[iminor(inode) >> 5];if (!handler || !(new_fops = fops_get(handler->fops))) {err = -ENODEV;goto out;}/* * That's _really_ odd. Usually NULL ->open means "nothing special", * not "no device". Oh, well... */if (!new_fops->open) {fops_put(new_fops);err = -ENODEV;goto out;}old_fops = file->f_op;/*定位fops*/file->f_op = new_fops;err = new_fops->open(inode, file);if (err) {fops_put(file->f_op);file->f_op = fops_get(old_fops);}fops_put(old_fops);out:unlock_kernel();return err;}通过此设备号所在的组(0~31)，(32~63),(64~95)……就可以找到相应的handler，所有的handler都保存在input_table中，对于次设备号在64~95范围的设备，将定位到下标为2的handler,，也就是event handler，然后将用handler中的open函数替代之前的open函数，并执行新的open函数，这样就以handler本身定义的open来打开设备完成相应的初始化了。event handler中的open函数：static int evdev_open(struct inode *inode, struct file *file){struct evdev *evdev;struct evdev_client *client;int i = iminor(inode) - EVDEV_MINOR_BASE;int error;if (i >= EVDEV_MINORS)return -ENODEV;error = mutex_lock_interruptible(&evdev_table_mutex);if (error)return error;/*从evdev_table中取出和此设备号对应的evdev实例*/evdev = evdev_table[i];if (evdev)get_device(&evdev->dev);mutex_unlock(&evdev_table_mutex);if (!evdev)return -ENODEV;/*每当一个应用程序打开该文件都会生成一个client*/client = kzalloc(sizeof(struct evdev_client), GFP_KERNEL);if (!client) {error = -ENOMEM;goto err_put_evdev;}spin_lock_init(&client->buffer_lock);client->evdev = evdev;/*将client链入evdev的client_list中*/evdev_attach_client(evdev, client);error = evdev_open_device(evdev);if (error)goto err_free_client;file->private_data = client;return 0; err_free_client:evdev_detach_client(evdev, client);kfree(client); err_put_evdev:put_device(&evdev->dev);return error;}static int evdev_open_device(struct evdev *evdev){int retval;retval = mutex_lock_interruptible(&evdev->mutex);if (retval)return retval;if (!evdev->exist)retval = -ENODEV;else if (!evdev->open++) {/*如果是第一次打开该设备，则要执行设备中定义的open*/retval = input_open_device(&evdev->handle);if (retval)evdev->open--;}mutex_unlock(&evdev->mutex);return retval;}int input_open_device(struct input_handle *handle){struct input_dev *dev = handle->dev;int retval;retval = mutex_lock_interruptible(&dev->mutex);if (retval)return retval;if (dev->going_away) {retval = -ENODEV;goto out;}handle->open++;if (!dev->users++ && dev->open)retval = dev->open(dev);//执行input_dev中定义的open，完成设备的初始化if (retval) {dev->users--;if (!--handle->open) {/* * Make sure we are not delivering any more events * through this handle */synchronize_rcu();}} out:mutex_unlock(&dev->mutex);return retval;}
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