上文介紹了input_dev 、input_handle、input_handler三者是如何聯系起來了,現在繼續介紹如何通過它們來傳遞資訊。
在開始之前還是先引用一位大俠的文章:
引:
現在看使用者擷取觸摸屏輸入的一個流程(以tsdev為例/drivers/input/tsdev.c):
static struct file_operations tsdev_fops = {
.owner = THIS_MODULE,
.open = tsdev_open,
.release = tsdev_release,
.read = tsdev_read,
.poll = tsdev_poll,
.fasync = tsdev_fasync,
.ioctl = tsdev_ioctl,
};
假設所有初始化早已完成,使用者open該裝置後,使用read系統調用進入核心,系統
轉移控制到tsdev_read,使用wait_event_interruptible等待事件。
此時驅動層得到使用者輸入,于是調用input_report_abs,input_report_abs隻是
input_event的簡單包裝:
static inline void input_report_abs(struct input_dev *dev,
unsigned int code, int value)
{
input_event(dev, EV_ABS, code, value);
}
void input_event(struct input_dev *dev, unsigned int type,
unsigned int code, int value)
{
...
switch (type) {
...
case EV_ABS:
...
break;
...
}
...
if (dev->grab)
dev->grab->handler->event(dev->grab, type, code, value);
else
list_for_each_entry(handle, &dev->h_list, d_node)
if (handle->open)
handle->handler->event(handle, type, code, value);
}
前面的處理關系具體裝置,見最後對handler函數的調用,就是從input_dev的h_list鍊
上的input_handle獲得每一個相關input_handler,并調用其中的event函數,對tsdev
來說:
static struct input_handler tsdev_handler = {
.event = tsdev_event,
.connect = tsdev_connect,
.disconnect = tsdev_disconnect,
.fops = &tsdev_fops,
.minor = TSDEV_MINOR_BASE,
.name = "tsdev",
.id_table = tsdev_ids,
};
即調用tsdev_event函數,接着看:
static void tsdev_event(struct input_handle *handle, unsigned int type,
unsigned int code, int value)
{
...
switch (type) {
case EV_ABS:
break;
...
list_for_each_entry(list, &tsdev->list, node) {
int x, y, tmp;
do_gettimeofday(&time);
list->event[list->head].millisecs = time.tv_usec / 100;
list->event[list->head].pressure = tsdev->pressure;
x = tsdev->x;
y = tsdev->y;
/* Calibration */
if (!list->raw) {
x = ((x * tsdev->cal.xscale) >> 8) + tsdev->cal.xtrans;
y = ((y * tsdev->cal.yscale) >> 8) + tsdev->cal.ytrans;
if (tsdev->cal.xyswap) {
tmp = x; x = y; y = tmp;
}
}
list->event[list->head].x = x;
list->event[list->head].y = y;
list->head = (list->head + 1) & (TSDEV_BUFFER_SIZE - 1);
kill_fasync(&list->fasync, SIGIO, POLL_IN);
}
wake_up_interruptible(&tsdev->wait);
}
它填充資料,并喚醒等待着的請求。于是前面等待着的read請求就可繼續了,
回到tsdev_read中,copy_to_user拷貝資料,最後傳回使用者層。
一個簡單流程就結束了。
注:
原文請看以下網址:
http://bbs.ustc.edu.cn/cgi/bbstcon?board=Kernel&file=M.1179398612.A
看了以上的内容,相信你對2.6核心的輸入子系統的消息傳遞過程應該有個大概的了解了,現在我就如何通過input_dev 、input_handle、input_handler這三者傳遞資訊進行詳細的分析:
################
從<tsdev.c>開始
################
static ssize_t tsdev_read(struct file *file, char __user *buffer, size_t count,
loff_t * ppos)
{
struct tsdev_list *list = file->private_data;
int retval = 0;
if (list->head == list->tail && list->tsdev->exist && (file->f_flags & O_NONBLOCK))
return -EAGAIN;
retval = wait_event_interruptible(list->tsdev->wait,
list->head != list->tail || !list->tsdev->exist);
if (retval)
return retval;
if (!list->tsdev->exist)
return -ENODEV;
while (list->head != list->tail &&
retval + sizeof (struct ts_event) <= count) {
if (copy_to_user (buffer + retval, list->event + list->tail,
sizeof (struct ts_event)))
return -EFAULT;
list->tail = (list->tail + 1) & (TSDEV_BUFFER_SIZE - 1);//更新讀指針
retval += sizeof (struct ts_event);//更新讀位元組數
}
return retval;
}
#################
<s3c2410-ts.c>
#################
input_report_abs(&ts.dev, ABS_X, ts.xp);
input_report_abs(&ts.dev, ABS_Y, ts.yp);
input_report_key(&ts.dev, BTN_TOUCH, 1);
input_report_abs(&ts.dev, ABS_PRESSURE, 1);
input_sync(&ts.dev);
###########################
<input.h>
###########################
static inline void input_report_abs(struct input_dev *dev, unsigned int code, int value)
{
input_event(dev, EV_ABS, code, value);
}
##########################
<input.c>
##########################
void input_event(struct input_dev *dev, unsigned int type, unsigned int code, int value)
{
struct input_handle *handle;
........................................................................................................
switch (type) {
case EV_ABS:
if (code > ABS_MAX || !test_bit(code, dev->absbit))//一些條件測試
return;
if (dev->absfuzz[code]) {
if ((value > dev->abs[code] - (dev->absfuzz[code] >> 1)) &&
(value < dev->abs[code] + (dev->absfuzz[code] >> 1)))
return;
if ((value > dev->abs[code] - dev->absfuzz[code]) &&
(value < dev->abs[code] + dev->absfuzz[code]))
value = (dev->abs[code] * 3 + value) >> 2;
if ((value > dev->abs[code] - (dev->absfuzz[code] << 1)) &&
(value < dev->abs[code] + (dev->absfuzz[code] << 1)))
value = (dev->abs[code] + value) >> 1;
}
if (dev->abs[code] == value)//比較目前值與上一次都值是否相同,相同則不作處理
return;
dev->abs[code] = value;//備份目前值,以便下一次作比較
break;
...............................................................................................................
if (type != EV_SYN)
dev->sync = 0;
if (dev->grab)
dev->grab->handler->event(dev->grab, type, code, value);
else
list_for_each_entry(handle, &dev->h_list, d_node)//通過input_dev找出與其聯系的input_handle
if (handle->open)//相應的接口裝置(比如tsdev)被打開(通過調用tsdev.c的tsdev_open函數進而調用input_open_device
函數增加handle->open的計數值)
handle->handler->event(handle, type, code, value);//調用該接口裝置的event函數對資料進行處理
}
################
在<tsdev.c>結束
################
static void tsdev_event(struct input_handle *handle, unsigned int type,
unsigned int code, int value)
{
struct tsdev *tsdev = handle->private;
struct tsdev_list *list;
struct timeval time;
switch (type) {
case EV_ABS:
switch (code) {
case ABS_X:
tsdev->x = value;//記錄x坐标值
break;
case ABS_Y:
tsdev->y = value;//記錄y坐标值
break;
case ABS_PRESSURE:
if (value > handle->dev->absmax[ABS_PRESSURE])
value = handle->dev->absmax[ABS_PRESSURE];
value -= handle->dev->absmin[ABS_PRESSURE];
if (value < 0)
value = 0;
tsdev->pressure = value;//記錄觸摸屏的按壓狀态
break;
}
break;
...................................................................................................
if (type != EV_SYN || code != SYN_REPORT)//鍵值的傳遞以EV_SYN為結束标志(通過input_sync函數),等到資料都填充好tsdev結構後再統一發送出去,否則直接傳回,繼續填充另一個資料
return;
list_for_each_entry(list, &tsdev->list, node) { //通過tsdev擷取struct tsdev_list結構(在tsdev_open函數中定義):
//list_add_tail(&list->node, &tsdev_table[i]->list);
int x, y, tmp;
do_gettimeofday(&time); //填充事件的時間
list->event[list->head].millisecs = time.tv_usec / 100;
list->event[list->head].pressure = tsdev->pressure;//填充觸摸屏的狀态
x = tsdev->x;
y = tsdev->y;
if (!list->raw) {
x = ((x * tsdev->cal.xscale) >> 8) + tsdev->cal.xtrans;
y = ((y * tsdev->cal.yscale) >> 8) + tsdev->cal.ytrans;
if (tsdev->cal.xyswap) {
tmp = x; x = y; y = tmp;
}
}
list->event[list->head].x = x; //填充x坐标值
list->event[list->head].y = y; //填充y坐标值
list->head = (list->head + 1) & (TSDEV_BUFFER_SIZE - 1);//更新寫指針
kill_fasync(&list->fasync, SIGIO, POLL_IN);
}
wake_up_interruptible(&tsdev->wait);//喚醒睡眠在tsdev->wait下等待資料都程序讀取資料。至此,資料傳遞過程結束,開始新一輪的資料傳遞。
}