Linux输入子系统分析（五）
输入事件驱动--->evdev_handler的实现
Linux输入子系统已经建立好了几个handler，用来处理几类常见的事件，如鼠标、键盘、摇杆等。其中最为基础的是evdev_handler，它是在driver/input/evdev.c中实现的。它能够接收任意类型的事件，任意id的设备都可以和它匹配连接，它对应的设备节点为/dev/eventX，次设备号的范围为64～95。
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#define EVDEV_MINOR_BASE64#define EVDEV_MINORS32#define EVDEV_MIN_BUFFER_SIZE64U#define EVDEV_BUF_PACKETS8
struct evdev {int open;int minor;struct input_handle handle;wait_queue_head_t wait;struct evdev_client __rcu *grab;struct list_head client_list;spinlock_t client_lock; /* protects client_list */struct mutex mutex;struct device dev;bool exist;};
struct evdev_client {int head;int tail;spinlock_t buffer_lock; /* protects access to buffer, head and tail */struct fasync_struct *fasync;struct evdev *evdev;struct list_head node;int bufsize;struct input_event buffer[]; //该处就是用于保存输入设备驱动通过input core传递过来的数据包};
static struct evdev *evdev_table[EVDEV_MINORS];static DEFINE_MUTEX(evdev_table_mutex);
/**evdev_pass_event()函数非常重要，输入设备驱动利用input_report_XX()把把事件数据包传递给事件驱动，最终就是通过调用*evdev_event，接着evdev_pass_event()实现把数据包发送过来的，保存在event_client->buffer中**/static void evdev_pass_event(struct evdev_client *client,struct input_event *event){/** Interrupts are disabled, just acquire the lock.* Make sure we don't leave with the client buffer* "empty" by having client->head == client->tail.*/spin_lock(&client->buffer_lock);do {client->buffer[client->head++] = *event;client->head &= client->bufsize - 1;} while (client->head == client->tail);spin_unlock(&client->buffer_lock);
if (event->type == EV_SYN)kill_fasync(&client->fasync, SIGIO, POLL_IN);}/** Pass incoming event to all connected clients.*/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;
do_gettimeofday(&event.time);event.type = type;event.code = code;event.value = value;
rcu_read_lock();
client = rcu_dereference(evdev->grab);if (client)evdev_pass_event(client, &event); //如上elselist_for_each_entry_rcu(client, &evdev->client_list, node)evdev_pass_event(client, &event);
rcu_read_unlock();
wake_up_interruptible(&evdev->wait);}
static int evdev_fasync(int fd, struct file *file, int on){..............................}
static int evdev_flush(struct file *file, fl_owner_t id){.................................}
static void evdev_free(struct device *dev){..............................}/** Grabs an event device (along with underlying input device).* This function is called with evdev->mutex taken.*/static int evdev_grab(struct evdev *evdev, struct evdev_client *client){int error;if (evdev->grab)return -EBUSY;
error = input_grab_device(&evdev->handle);if (error)return error;
rcu_assign_pointer(evdev->grab, client);synchronize_rcu();return 0;}
static int evdev_ungrab(struct evdev *evdev, struct evdev_client *client){.......................}
static void evdev_attach_client(struct evdev *evdev,struct evdev_client *client){spin_lock(&evdev->client_lock);list_add_tail_rcu(&client->node, &evdev->client_list);spin_unlock(&evdev->client_lock);synchronize_rcu();}
static void evdev_detach_client(struct evdev *evdev,struct evdev_client *client){spin_lock(&evdev->client_lock);list_del_rcu(&client->node);spin_unlock(&evdev->client_lock);synchronize_rcu();}
static int evdev_open_device(struct evdev *evdev){,..................................}
static void evdev_close_device(struct evdev *evdev){.....................................}/** Wake up users waiting for IO so they can disconnect from* dead device.*/static void evdev_hangup(struct evdev *evdev){.....................}
static int evdev_release(struct inode *inode, struct file *file){..........................................}
static unsigned int evdev_compute_buffer_size(struct input_dev *dev){............................................}
static int evdev_open(struct inode *inode, struct file *file){struct evdev *evdev;struct evdev_client *client;int i = iminor(inode) - EVDEV_MINOR_BASE;unsigned int bufsize;int error;
if (i >= EVDEV_MINORS)return -ENODEV;
error = mutex_lock_interruptible(&evdev_table_mutex);if (error)return error;evdev = evdev_table[i];if (evdev)get_device(&evdev->dev);mutex_unlock(&evdev_table_mutex);
if (!evdev)return -ENODEV;
bufsize = evdev_compute_buffer_size(evdev->handle.dev);
client = kzalloc(sizeof(struct evdev_client) +bufsize * sizeof(struct input_event),GFP_KERNEL);if (!client) {error = -ENOMEM;goto err_put_evdev;}
client->bufsize = bufsize;spin_lock_init(&client->buffer_lock);client->evdev = evdev;evdev_attach_client(evdev, client);
error = evdev_open_device(evdev);if (error)goto err_free_client;
file->private_data = client;nonseekable_open(inode, file);
return 0;
err_free_client:evdev_detach_client(evdev, client);kfree(client);err_put_evdev:put_device(&evdev->dev);return error;}
static ssize_t evdev_write(struct file *file, const char __user *buffer,size_t count, loff_t *ppos){..............................................}
static int evdev_fetch_next_event(struct evdev_client *client,struct input_event *event){..............................}
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 &&(file->f_flags & O_NONBLOCK))return -EAGAIN;
retval = wait_event_interruptible(evdev->wait,client->head != client->tail || !evdev->exist);if (retval)return retval;
if (!evdev->exist)return -ENODEV;
while (retval + input_event_size() <= count &&evdev_fetch_next_event(client, &event)) {
if (input_event_to_user(buffer + retval, &event))return -EFAULT;
retval += input_event_size();}return retval;}
/* No kernel lock - fine */static unsigned int evdev_poll(struct file *file, poll_table *wait){.............................}#ifdef CONFIG_COMPAT#define BITS_PER_LONG_COMPAT (sizeof(compat_long_t) * 8)#define BITS_TO_LONGS_COMPAT(x) ((((x) - 1) / BITS_PER_LONG_COMPAT) + 1)#ifdef __BIG_ENDIANstatic int bits_to_user(unsigned long *bits, unsigned int maxbit,unsigned int maxlen, void __user *p, int compat){int len, i;
if (compat) {len = BITS_TO_LONGS_COMPAT(maxbit) * sizeof(compat_long_t);if (len > maxlen)len = maxlen;
for (i = 0; i < len / sizeof(compat_long_t); i++)if (copy_to_user((compat_long_t __user *) p + i,(compat_long_t *) bits +i + 1 - ((i % 2) << 1),sizeof(compat_long_t)))return -EFAULT;} else {len = BITS_TO_LONGS(maxbit) * sizeof(long);if (len > maxlen)len = maxlen;
if (copy_to_user(p, bits, len))return -EFAULT;}
return len;}#elsestatic int bits_to_user(unsigned long *bits, unsigned int maxbit,unsigned int maxlen, void __user *p, int compat){int len = compat ?BITS_TO_LONGS_COMPAT(maxbit) * sizeof(compat_long_t) :BITS_TO_LONGS(maxbit) * sizeof(long);
if (len > maxlen)len = maxlen;
return copy_to_user(p, bits, len) ? -EFAULT : len;}#endif /* __BIG_ENDIAN */
#else
static int bits_to_user(unsigned long *bits, unsigned int maxbit,unsigned int maxlen, void __user *p, int compat){int len = BITS_TO_LONGS(maxbit) * sizeof(long);
if (len > maxlen)len = maxlen;
return copy_to_user(p, bits, len) ? -EFAULT : len;}
#endif /* CONFIG_COMPAT */
static int str_to_user(const char *str, unsigned int maxlen, void __user *p){int len;
if (!str)return -ENOENT;
len = strlen(str) + 1;if (len > maxlen)len = maxlen;
return copy_to_user(p, str, len) ? -EFAULT : len;}
#define OLD_KEY_MAX0x1ffstatic int handle_eviocgbit(struct input_dev *dev,unsigned int type, unsigned int size,void __user *p, int compat_mode){static unsigned long keymax_warn_time;unsigned long *bits;int len;
switch (type) {
case 0: bits = dev->evbit; len = EV_MAX; break;case EV_KEY: bits = dev->keybit; len = KEY_MAX; break;case EV_REL: bits = dev->relbit; len = REL_MAX; break;case EV_ABS: bits = dev->absbit; len = ABS_MAX; break;case EV_MSC: bits = dev->mscbit; len = MSC_MAX; break;case EV_LED: bits = dev->ledbit; len = LED_MAX; break;case EV_SND: bits = dev->sndbit; len = SND_MAX; break;case EV_FF: bits = dev->ffbit; len = FF_MAX; break;case EV_SW: bits = dev->swbit; len = SW_MAX; break;default: return -EINVAL;}
/** Work around bugs in userspace programs that like to do* EVIOCGBIT(EV_KEY, KEY_MAX) and not realize that 'len'* should be in bytes, not in bits.*/if (type == EV_KEY && size == OLD_KEY_MAX) {len = OLD_KEY_MAX;if (printk_timed_ratelimit(&keymax_warn_time, 10 * 1000))pr_warning("(EVIOCGBIT): Suspicious buffer size %u, ""limiting output to %zu bytes. See ""http://userweb.kernel.org/~dtor/eviocgbit-bug.html\n",OLD_KEY_MAX,BITS_TO_LONGS(OLD_KEY_MAX) * sizeof(long));}
return bits_to_user(bits, len, size, p, compat_mode);}#undef OLD_KEY_MAX
static int evdev_handle_get_keycode(struct input_dev *dev, void __user *p){struct input_keymap_entry ke = {.len= sizeof(unsigned int),.flags= 0,};int __user *ip = (int __user *)p;int error;
/* legacy case */if (copy_from_user(ke.scancode, p, sizeof(unsigned int)))return -EFAULT;
error = input_get_keycode(dev, &ke);if (error)return error;
if (put_user(ke.keycode, ip + 1))return -EFAULT;
return 0;}
static int evdev_handle_get_keycode_v2(struct input_dev *dev, void __user *p){struct input_keymap_entry ke;int error;
if (copy_from_user(&ke, p, sizeof(ke)))return -EFAULT;
error = input_get_keycode(dev, &ke);if (error)return error;if (copy_to_user(p, &ke, sizeof(ke)))return -EFAULT;
return 0;}
static int evdev_handle_set_keycode(struct input_dev *dev, void __user *p){struct input_keymap_entry ke = {.len= sizeof(unsigned int),.flags= 0,};int __user *ip = (int __user *)p;
if (copy_from_user(ke.scancode, p, sizeof(unsigned int)))return -EFAULT;
if (get_user(ke.keycode, ip + 1))return -EFAULT;return input_set_keycode(dev, &ke);}
static int evdev_handle_set_keycode_v2(struct input_dev *dev, void __user *p){struct input_keymap_entry ke;
if (copy_from_user(&ke, p, sizeof(ke)))return -EFAULT;
if (ke.len > sizeof(ke.scancode))return -EINVAL;return input_set_keycode(dev, &ke);}
static long evdev_do_ioctl(struct file *file, unsigned int cmd,void __user *p, int compat_mode){struct evdev_client *client = file->private_data;struct evdev *evdev = client->evdev;struct input_dev *dev = evdev->handle.dev;struct input_absinfo abs;struct ff_effect effect;int __user *ip = (int __user *)p;unsigned int i, t, u, v;unsigned int size;int error;
/* First we check for fixed-length commands */switch (cmd) {
case EVIOCGVERSION:return put_user(EV_VERSION, ip);
case EVIOCGID:if (copy_to_user(p, &dev->id, sizeof(struct input_id)))return -EFAULT;return 0;
case EVIOCGREP:if (!test_bit(EV_REP, dev->evbit))return -ENOSYS;if (put_user(dev->rep[REP_DELAY], ip))return -EFAULT;if (put_user(dev->rep[REP_PERIOD], ip + 1))return -EFAULT;return 0;
case EVIOCSREP:if (!test_bit(EV_REP, dev->evbit))return -ENOSYS;if (get_user(u, ip))return -EFAULT;if (get_user(v, ip + 1))return -EFAULT;
input_inject_event(&evdev->handle, EV_REP, REP_DELAY, u);input_inject_event(&evdev->handle, EV_REP, REP_PERIOD, v);
return 0;case EVIOCRMFF:return input_ff_erase(dev, (int)(unsigned long) p, file);
case EVIOCGEFFECTS:i = test_bit(EV_FF, dev->evbit) ?dev->ff->max_effects : 0;if (put_user(i, ip))return -EFAULT;return 0;
case EVIOCGRAB:if (p)return evdev_grab(evdev, client);elsereturn evdev_ungrab(evdev, client);
case EVIOCGKEYCODE:return evdev_handle_get_keycode(dev, p);
case EVIOCSKEYCODE:return evdev_handle_set_keycode(dev, p);
case EVIOCGKEYCODE_V2:return evdev_handle_get_keycode_v2(dev, p);
case EVIOCSKEYCODE_V2:return evdev_handle_set_keycode_v2(dev, p);}
size = _IOC_SIZE(cmd);
/* Now check variable-length commands */#define EVIOC_MASK_SIZE(nr)((nr) & ~(_IOC_SIZEMASK << _IOC_SIZESHIFT))switch (EVIOC_MASK_SIZE(cmd)) {
case EVIOCGPROP(0):return bits_to_user(dev->propbit, INPUT_PROP_MAX,size, p, compat_mode);
case EVIOCGKEY(0):return bits_to_user(dev->key, KEY_MAX, size, p, compat_mode);
case EVIOCGLED(0):return bits_to_user(dev->led, LED_MAX, size, p, compat_mode);
case EVIOCGSND(0):return bits_to_user(dev->snd, SND_MAX, size, p, compat_mode);
case EVIOCGSW(0):return bits_to_user(dev->sw, SW_MAX, size, p, compat_mode);
case EVIOCGNAME(0):return str_to_user(dev->name, size, p);
case EVIOCGPHYS(0):return str_to_user(dev->phys, size, p);
case EVIOCGUNIQ(0):return str_to_user(dev->uniq, size, p);
case EVIOC_MASK_SIZE(EVIOCSFF):if (input_ff_effect_from_user(p, size, &effect))return -EFAULT;
error = input_ff_upload(dev, &effect, file);
if (put_user(effect.id, &(((struct ff_effect __user *)p)->id)))return -EFAULT;
return error;}
/* Multi-number variable-length handlers */if (_IOC_TYPE(cmd) != 'E')return -EINVAL;
if (_IOC_DIR(cmd) == _IOC_READ) {
if ((_IOC_NR(cmd) & ~EV_MAX) == _IOC_NR(EVIOCGBIT(0, 0)))return handle_eviocgbit(dev,_IOC_NR(cmd) & EV_MAX, size,p, compat_mode);
if ((_IOC_NR(cmd) & ~ABS_MAX) == _IOC_NR(EVIOCGABS(0))) {
if (!dev->absinfo)return -EINVAL;
t = _IOC_NR(cmd) & ABS_MAX;abs = dev->absinfo[t];
if (copy_to_user(p, &abs, min_t(size_t,size, sizeof(struct input_absinfo))))return -EFAULT;
return 0;}}
if (_IOC_DIR(cmd) == _IOC_WRITE) {
if ((_IOC_NR(cmd) & ~ABS_MAX) == _IOC_NR(EVIOCSABS(0))) {
if (!dev->absinfo)return -EINVAL;
t = _IOC_NR(cmd) & ABS_MAX;
if (copy_from_user(&abs, p, min_t(size_t,size, sizeof(struct input_absinfo))))return -EFAULT;
if (size < sizeof(struct input_absinfo))abs.resolution = 0;
/* We can't change number of reserved MT slots */if (t == ABS_MT_SLOT)return -EINVAL;
/** Take event lock to ensure that we are not* changing device parameters in the middle* of event.*/spin_lock_irq(&dev->event_lock);dev->absinfo[t] = abs;spin_unlock_irq(&dev->event_lock);
return 0;}}return -EINVAL;}static long evdev_ioctl_handler(struct file *file, unsigned int cmd,void __user *p, int compat_mode){struct evdev_client *client = file->private_data;struct evdev *evdev = client->evdev;int retval;
retval = mutex_lock_interruptible(&evdev->mutex);if (retval)return retval;
if (!evdev->exist) {retval = -ENODEV;goto out;}
retval = evdev_do_ioctl(file, cmd, p, compat_mode)；
out:mutex_unlock(&evdev->mutex);return retval;}
static long evdev_ioctl(struct file *file, unsigned int cmd, unsigned long arg){return evdev_ioctl_handler(file, cmd, (void __user *)arg, 0);}
#ifdef CONFIG_COMPATstatic long evdev_ioctl_compat(struct file *file,unsigned int cmd, unsigned long arg){return evdev_ioctl_handler(file, cmd, compat_ptr(arg), 1);}#endif
/**一般事件驱动完成加载到内核后，都生成/dev/input/eventX这样一个设备文件，既然是一个设备文件当然涉及到相关的*操作，以下evdev_fops结构就描述了eventX支持的文件操作，当用户调用open（“/dev/input/eventX”，“O_RDONLY”）*最终使调用evdev_open函数。*/static const struct file_operations evdev_fops = {.owner= THIS_MODULE,.read= evdev_read,.write= evdev_write,.poll= evdev_poll,.open= evdev_open,.release= evdev_release,.unlocked_ioctl= evdev_ioctl,#ifdef CONFIG_COMPAT.compat_ioctl= evdev_ioctl_compat,#endif.fasync= evdev_fasync,.flush= evdev_flush,.llseek= no_llseek,};
static int evdev_install_chrdev(struct evdev *evdev){/** No need to do any locking here as calls to connect and* disconnect are serialized by the input core*/evdev_table[evdev->minor] = evdev;return 0;}
static void evdev_remove_chrdev(struct evdev *evdev){/** Lock evdev table to prevent race with evdev_open()*/mutex_lock(&evdev_table_mutex);evdev_table[evdev->minor] = NULL;mutex_unlock(&evdev_table_mutex);}
/** Mark device non-existent. This disables writes, ioctls and* prevents new users from opening the device. Already posted* blocking reads will stay, however new ones will fail.*/static void evdev_mark_dead(struct evdev *evdev){mutex_lock(&evdev->mutex);evdev->exist = false;mutex_unlock(&evdev->mutex);}
static void evdev_cleanup(struct evdev *evdev){struct input_handle *handle = &evdev->handle;
evdev_mark_dead(evdev);evdev_hangup(evdev);evdev_remove_chrdev(evdev);
/* evdev is marked dead so no one else accesses evdev->open */if (evdev->open) {input_flush_device(handle, NULL);input_close_device(handle);}}
/** Create new evdev device. Note that input core serializes calls* to connect and disconnect so we don't need to lock evdev_table here.*//**不管是事件驱动还是输入设备驱动在初始化时注册自身到全局链表中，并尝试与对应的输入设备驱动或事件驱动连接，*最终的操作都是调用事件驱动的XX_connect(...)完成两者的连接的。*/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) {pr_err("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 = true;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;
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);
/**input_register_handle()最终完成了两者的连接*具体实现可研究其实现源码*/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);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;}
/**断开输入设备驱动与输入事件驱动的连接*/static void evdev_disconnect(struct input_handle *handle){struct evdev *evdev = handle->private;
device_del(&evdev->dev);evdev_cleanup(evdev);input_unregister_handle(handle);put_device(&evdev->dev);}
/**一般事件驱动定义了evdev_handler结构表示自己，然后填充好该结构如下所示。*接下来就是调用input_register_handler（&evdev_handler）注册evdev_handler到全局链表input_handler_list中，*并尝试去找到与handler中id_table相匹配的输入设备。*/st atic const struct input_device_id evdev_ids[] = {{ .driver_info = 1 },/* Matches all devices */{ },/* Terminating zero entry */};
MODULE_DEVICE_TABLE(input, evdev_ids);
static struct input_handler evdev_handler = {.event = evdev_event,.connect = evdev_connect,.disconnect = evdev_disconnect,.fops = &evdev_fops, //所支持的用户操作（open/read/write等）.minor = EVDEV_MINOR_BASE,.name = "evdev",.id_table = evdev_ids,};
//初始化evdev_handlerstatic int __init evdev_init(void){return input_register_handler(&evdev_handler);}
static void __exit evdev_exit(void){input_unregister_handler(&evdev_handler);}
module_init(evdev_init);module_exit(evdev_exit);