水平有限,描述不当之处还请指出,转载请注明出处http://blog.csdn.net/vanbreaker/article/details/7718158
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; }