Xorg Handler简介

简介

Xorg Handler用于处理各种类型的回调函数，Xorg一共支持四种类型的Handler：

BlockHandler： 在阻塞之前调用；
WakeupHandler： 在唤醒之后调用；
InputHandler： 用于键盘鼠标等输入设备；
GeneralHandler： 用于其它类型的设备；

其中BlockHandler和WakeupHandler属于同一种类型，它们的回调函数不需要关联设备文件句柄，并且一旦注册上就会无条件执行。

InputHandler和GeneralHandler属于另一种类型，它们的回调函数需要关联到某一个设备句柄(例如键盘设备文件)，当设备句柄有数据到达时，可以马上唤醒阻塞中的Xorg，并且只有在设备句柄可读/可写时，对应的回调函数才会执行。

注册BlockHandler和WakeupHandler

RegisterBlockAndWakeupHandlers

BlockHandler和WakeupHandler通过调用RegisterBlockAndWakeupHandlers函数注册，该函数同时注册两个回调函数，通过往static数组handlers增加一个成员实现：

Bool
RegisterBlockAndWakeupHandlers(BlockHandlerProcPtr blockHandler,WakeupHandlerProcPtr wakeupHandler,void *blockData)
{BlockHandlerPtr new;if (numHandlers >= sizeHandlers) {new = (BlockHandlerPtr) realloc(handlers, (numHandlers + 1) *sizeof(BlockHandlerRec));if (!new)return FALSE;handlers = new;sizeHandlers = numHandlers + 1;}handlers[numHandlers].BlockHandler = blockHandler;handlers[numHandlers].WakeupHandler = wakeupHandler;handlers[numHandlers].blockData = blockData;handlers[numHandlers].deleted = FALSE;numHandlers = numHandlers + 1;return TRUE;
}

注册到Screen

除了调用上面的函数注册到handlers，也可以通过直接修改指针注册到Screen，典型代码如下：

/** Setup points to the block and wakeup handlers.  Pass a pointer* to the current screen as pWakeupdata.*/
pScreen->BlockHandler = winBlockHandler;
pScreen->WakeupHandler = winWakeupHandler;

如果使用直接修改指针的方式注册，需要在修改之前保存原始指针，退出时进行还原。这两种注册方式使用场景也有差别，第二种注册的回调函数与对应的Screen绑定，第一种注册方式没有绑定。

注册InputHandler

InputHandler通过调用xf86AddInputHandler函数注册，该函数在InputHandlers链表中增加一个成员。

static void *
addInputHandler(int fd, InputHandlerProc proc, void *data)
{IHPtr ih;if (fd < 0 || !proc)return NULL;ih = calloc(sizeof(*ih), 1);if (!ih)return NULL;ih->fd = fd;ih->ihproc = proc;ih->data = data;ih->enabled = TRUE;ih->next = InputHandlers;InputHandlers = ih;return ih;
}void *
xf86AddInputHandler(int fd, InputHandlerProc proc, void *data)
{IHPtr ih = addInputHandler(fd, proc, data);if (ih) {AddEnabledDevice(fd);ih->is_input = TRUE;}return ih;
}

注册GeneralHandler

GeneralHandler通过调用xf86AddGeneralHandler函数注册。该函数与xf86AddInputHandler一样，内部也是通过调用addInputHandler实现，不同的是InputHandler被标记为输入设备，除此之外没有其它差别。

void *
xf86AddGeneralHandler(int fd, InputHandlerProc proc, void *data)
{IHPtr ih = addInputHandler(fd, proc, data);if (ih)AddGeneralSocket(fd);return ih;
}

Handler的执行

Handler执行流程如下图所示，在WaitForSomething函数中先调用BlockHandler执行所有block类型的handler，然后执行select等待输入事件，select阻塞结束后执行WakeupHandler执行所有wakeup类型的handler。InputHandler和GeneralHandler由xf86Wakeup函数执行，该函数在Xorg初始化时会被注册为一个WakeupHandler。

BlockHandler函数

void
BlockHandler(void *pTimeout, void *pReadmask)
{int i, j;++inHandler;for (i = 0; i < screenInfo.numScreens; i++)(*screenInfo.screens[i]->BlockHandler) (screenInfo.screens[i],pTimeout, pReadmask);for (i = 0; i < screenInfo.numGPUScreens; i++)(*screenInfo.gpuscreens[i]->BlockHandler) (screenInfo.gpuscreens[i],pTimeout, pReadmask);for (i = 0; i < numHandlers; i++)if (!handlers[i].deleted)(*handlers[i].BlockHandler) (handlers[i].blockData,pTimeout, pReadmask);if (handlerDeleted) {for (i = 0; i < numHandlers;)if (handlers[i].deleted) {for (j = i; j < numHandlers - 1; j++)handlers[j] = handlers[j + 1];numHandlers--;}elsei++;handlerDeleted = FALSE;}--inHandler;
}

WakeupHandler函数

void
WakeupHandler(int result, void *pReadmask)
{int i, j;++inHandler;for (i = numHandlers - 1; i >= 0; i--)if (!handlers[i].deleted)(*handlers[i].WakeupHandler) (handlers[i].blockData,result, pReadmask);for (i = 0; i < screenInfo.numScreens; i++)(*screenInfo.screens[i]->WakeupHandler) (screenInfo.screens[i],result, pReadmask);for (i = 0; i < screenInfo.numGPUScreens; i++)(*screenInfo.gpuscreens[i]->WakeupHandler) (screenInfo.gpuscreens[i],result, pReadmask);if (handlerDeleted) {for (i = 0; i < numHandlers;)if (handlers[i].deleted) {for (j = i; j < numHandlers - 1; j++)handlers[j] = handlers[j + 1];numHandlers--;}elsei++;handlerDeleted = FALSE;}--inHandler;
}

xf86Wakeup函数

Xorg在初始化时调用RegisterBlockAndWakeupHandlers((BlockHandlerProcPtr) NoopDDA, xf86Wakeup, NULL);注册xf86Wakeup。

void
xf86Wakeup(void *blockData, int err, void *pReadmask)
{fd_set *LastSelectMask = (fd_set *) pReadmask;fd_set devicesWithInput;InputInfoPtr pInfo;if (err >= 0) {XFD_ANDSET(&devicesWithInput, LastSelectMask, &EnabledDevices);if (XFD_ANYSET(&devicesWithInput)) {pInfo = xf86InputDevs;while (pInfo) {if (pInfo->read_input && pInfo->fd >= 0 &&(FD_ISSET(pInfo->fd, &devicesWithInput) != 0)) {OsBlockSIGIO();/** Remove the descriptior from the set because more than one* device may share the same file descriptor.*/FD_CLR(pInfo->fd, &devicesWithInput);pInfo->read_input(pInfo);OsReleaseSIGIO();}pInfo = pInfo->next;}}}if (err >= 0) {             /* we don't want the handlers called if select() */IHPtr ih, ih_tmp;       /* returned with an error condition, do we?      */nt_list_for_each_entry_safe(ih, ih_tmp, InputHandlers, next) {if (ih->enabled && ih->fd >= 0 && ih->ihproc &&(FD_ISSET(ih->fd, ((fd_set *) pReadmask)) != 0)) {ih->ihproc(ih->fd, ih->data);}}}if (xf86VTSwitchPending())xf86VTSwitch();
}