WinCE6.0 DEVICEEMULATOR BSP的BackLight驱动简析

这里就WinCE6.0 DEVICEEMULATOR BSP的BackLight驱动做下分析, 更多关于电源管理的内容可以参考其他资料.一篇不错的文章是:
http://www.cnblogs.com/we-hjb/archive/2010/01/27/1657973.html
首先在GEC2410.bat中打开BackLight的支持
set BSP_NOBACKLIGHT=
这是一个名称为BKL的流接口驱动,实际上流接口函数,如BKL_Open, BKL_Read, BKL_Read,BKL_Write等都未实现,只有一个空函数框架,因为背光驱动并没有数据的输入输出,而是具体的功能设置.
因此实现的就是BKL_IOControl函数,有4种IOCTL Code:IOCTL_POWER_CAPABILITIES, IOCTL_POWER_QUERY, IOCTL_POWER_SET, IOCTL_POWER_GET.
整个函数代码如下:
extern "C" BOOL BKL_IOControl( DWORD hOpenContext, DWORD dwCode, PBYTE pBufIn, DWORD dwLenIn, PBYTE pBufOut, DWORD dwLenOut, PDWORD pdwActualOut ) { DWORD dwErr = ERROR_INVALID_PARAMETER; RETAILMSG(ZONE_BACKLIGHT,(TEXT("BKL_IOControl IOCTL code = %d/r/n"), dwCode)); switch (dwCode) { case IOCTL_POWER_CAPABILITIES: // determines device-specific capabilities RETAILMSG(ZONE_BACKLIGHT, (TEXT("BKL: Received IOCTL_POWER_CAPABILITIES/r/n"))); if (pBufOut && dwLenOut >= sizeof (POWER_CAPABILITIES) && pdwActualOut) { __try { PPOWER_CAPABILITIES PowerCaps = (PPOWER_CAPABILITIES)pBufOut; // Right now supports D0 (permanently on) and D4(off) only. memset(PowerCaps, 0, sizeof(*PowerCaps)); PowerCaps->DeviceDx = 0x11; //support D0, D4 *pdwActualOut = sizeof(*PowerCaps); dwErr = ERROR_SUCCESS; } __except(EXCEPTION_EXECUTE_HANDLER) { RETAILMSG(ZONE_BACKLIGHT, (TEXT("exception in ioctl/r/n"))); } } break; case IOCTL_POWER_QUERY: // determines whether changing power state is feasible RETAILMSG(ZONE_BACKLIGHT,(TEXT("BKL: Received IOCTL_POWER_QUERY/r/n"))); if (pBufOut && dwLenOut >= sizeof(CEDEVICE_POWER_STATE)) { // Return a good status on any valid query, since we are always ready to // change power states (if asked for state we don't support, we move to next highest, eg D3->D4). __try { CEDEVICE_POWER_STATE ReqDx = *(PCEDEVICE_POWER_STATE)pBufOut; if (VALID_DX(ReqDx)) { // This is a valid Dx state so return a good status. dwErr = ERROR_SUCCESS; } RETAILMSG(ZONE_BACKLIGHT, (TEXT("IOCTL_POWER_QUERY %s/r/n"), dwErr == ERROR_SUCCESS ? (TEXT("succeeded")) : (TEXT("failed")) )); } __except(EXCEPTION_EXECUTE_HANDLER) { RETAILMSG(ZONE_BACKLIGHT, (TEXT("Exception in ioctl/r/n"))); } } break; break; case IOCTL_POWER_SET: // requests a change from one device power state to another RETAILMSG(ZONE_BACKLIGHT,(TEXT("BKL: Received IOCTL_POWER_SET/r/n"))); if (pBufOut && dwLenOut >= sizeof(CEDEVICE_POWER_STATE)) { __try { CEDEVICE_POWER_STATE ReqDx = *(PCEDEVICE_POWER_STATE)pBufOut; if (VALID_DX(ReqDx)) { if(ReqDx == D1 ||ReqDx == D2 || ReqDx == D3) { ReqDx = D4; } if (SetBackLightState(D0 == ReqDx ? TRUE : FALSE)) { *(PCEDEVICE_POWER_STATE) pBufOut = ReqDx; *pdwActualOut = sizeof(CEDEVICE_POWER_STATE); dwErr = ERROR_SUCCESS; RETAILMSG(ZONE_BACKLIGHT, (TEXT("IOCTL_POWER_SET to D%u /r/n"), ReqDx)); } else { dwErr = GetLastError(); RETAILMSG(ZONE_BACKLIGHT, (TEXT("IOCTL_POWER_SET failed to switch to D%u/r/n"), ReqDx)); } } else { RETAILMSG(ZONE_BACKLIGHT, (TEXT("Invalid state request D%u/r/n"), ReqDx)); } } __except(EXCEPTION_EXECUTE_HANDLER) { RETAILMSG(ZONE_BACKLIGHT, (TEXT("Exception in ioctl/r/n"))); } } break; break; case IOCTL_POWER_GET: // gets the current device power state RETAILMSG(ZONE_BACKLIGHT,(TEXT("BKL: Received IOCTL_POWER_GET/r/n"))); if (pBufOut != NULL && dwLenOut >= sizeof(CEDEVICE_POWER_STATE)) { __try { if (GetBackLightState((PCEDEVICE_POWER_STATE)pBufOut)) { dwErr = ERROR_SUCCESS; RETAILMSG(ZONE_BACKLIGHT, (TEXT("IOCTL_POWER_GET: passing back %u/r/n"), *(PCEDEVICE_POWER_STATE)pBufOut)); } else { dwErr = GetLastError(); RETAILMSG(ZONE_BACKLIGHT, (TEXT("IOCTL_POWER_GET: failed to get backlight state/r/n"))); } } __except(EXCEPTION_EXECUTE_HANDLER) { RETAILMSG(ZONE_BACKLIGHT, (TEXT("Exception in ioctl/r/n"))); } } break; default: break; } if (dwErr) { RETAILMSG(ZONE_BACKLIGHT, (TEXT("Ioctl failed - err=%d/r/n"), dwErr)); return FALSE; } return TRUE; }
函数结构很简单,我们根据IOCTL Code分成4部分来看:
1. IOCTL_POWER_CAPABILITIES(查看背光设备支持的电源状态):
首先检查了输出参数,然后定义了一个PPOWER_CAPABILITIES结构的指针变量PowerCaps,赋值为实际的输出buffer
PPOWER_CAPABILITIES PowerCaps = (PPOWER_CAPABILITIES)pBufOut;
PPOWER_CAPABILITIES的原型是:
typedef struct _POWER_CAPABILITIES { UCHAR DeviceDx; UCHAR WakeFromDx; UCHAR InrushDx; DWORD Power[5]; DWORD Latency[5]; DWORD Flags; } POWER_CAPABILITIES, *PPOWER_CAPABILITIES;
其中DeviceDx代表的是设备支持的电源状态位, 其他具体的成员含义可参考帮助.
memset(PowerCaps, 0, sizeof(*PowerCaps));//初始化为0 PowerCaps->DeviceDx = 0x11; //support D0(on), D4(off),这里只支持这两种状态 *pdwActualOut = sizeof(*PowerCaps);//实际输出数据的大小
这个IOCTL会在驱动加载时被PM调用来获取设备驱动支持的电源状态.

2. IOCTL_POWER_QUERY(检查背光设备电源状态是否可查询)
通过CEDEVICE_POWER_STATE枚举类型的变量ReqDx来检查状态是否有效,其中CEDEVICE_POWER_STATE原型为:
即电源状态的定义.
typedef enum _CEDEVICE_POWER_STATE { PwrDeviceUnspecified = -1, D0 = 0, D1, D2, D3, D4, PwrDeviceMaximum } CEDEVICE_POWER_STATE, *PCEDEVICE_POWER_STATE;
CEDEVICE_POWER_STATE ReqDx = *(PCEDEVICE_POWER_STATE)pBufOut;
 
if (VALID_DX(ReqDx)) 
{
        // This is a valid Dx state so return a good status.
        dwErr = ERROR_SUCCESS;
}

3. IOCTL_POWER_SET(改变背光电源状态)
(1) 首先获得当前的电源状态:
CEDEVICE_POWER_STATE ReqDx = *(PCEDEVICE_POWER_STATE)pBufOut;
(2) VALID_DX验证ReqDx 有效后,如果状态为D1,D2,D3则一律修改为D4(因为只支持D0,D4)
 if(ReqDx == D1 ||ReqDx == D2 || ReqDx == D3)
{
    ReqDx = D4;
}
(3) 调用SetBackLightState修改背光状态,根据ReqDx是D0与否打开或者关闭背光,并更新相应输出参数状态.
 if (SetBackLightState(D0 == ReqDx ? TRUE : FALSE))
{
         *(PCEDEVICE_POWER_STATE) pBufOut = ReqDx;
         *pdwActualOut = sizeof(CEDEVICE_POWER_STATE);
 
         dwErr = ERROR_SUCCESS;
         RETAILMSG(ZONE_BACKLIGHT, (TEXT("IOCTL_POWER_SET to D%u /r/n"), ReqDx));
}

4.IOCTL_POWER_GET(获取背光电源状态)
参数检查后调用GetBackLightState将当前背光状态赋值给输出pBufOut
if (GetBackLightState((PCEDEVICE_POWER_STATE)pBufOut))
{
         dwErr = ERROR_SUCCESS;
 
          RETAILMSG(ZONE_BACKLIGHT, (TEXT("IOCTL_POWER_GET: passing back %u/r/n"), *(PCEDEVICE_POWER_STATE)pBufOut));
}

5. SetBackLightState和GetBackLightState
接着看看SetBackLightState和GetBackLightState的具体实现.
(1) SetBackLightState
首先创建HDC句柄,然后可以通过这个句柄来访问LCD驱动, 这里调用的是ExtEscape函数来设置背光电源状态.最后删除释放该句柄.其中第二个参数为SETBACKLIGHT还是GETBACKLIGHT表示是设置还是获取背光状态.
BOOL SetBackLightState(BOOL fBacklightOn) { // Call the display driver to change the backlight state HDC hdc = CreateDC(NULL, NULL, NULL, NULL); // This gets us a HDC to the screen. if (hdc == NULL) { return FALSE; } int iRet = ExtEscape(hdc, SETBACKLIGHT, sizeof(fBacklightOn), (LPCSTR)&fBacklightOn, 0, NULL); DeleteDC(hdc); return (iRet > 0) ? TRUE : FALSE; }
(2)GetBackLightState
和SetBackLightState,通过ExtEscape来获得当前背光状态.BOOL GetBackLightState(PCEDEVICE_POWER_STATE pState) { // Call the display driver to change the backlight state HDC hdc = CreateDC(NULL, NULL, NULL, NULL); // This gets us a HDC to the screen. if (hdc == NULL) { return FALSE; } BOOL fBacklightOn; int iRet = ExtEscape(hdc, GETBACKLIGHT, 0, NULL, sizeof(fBacklightOn), (LPSTR)&fBacklightOn); DeleteDC(hdc); if (iRet > 0) { *pState = (fBacklightOn) ? D0 : D4; return TRUE; } return FALSE; }
(3)LCD驱动DrvEscape函数
调用了ExtEscape实际上调用的就是LCD驱动中的DrvEscape函数,在LCD驱动s3c2410x_lcd.cpp中可以看到,根据输入参数是SETBACKLIGHT还是GETBACKLIGHT来设置LCD寄存器来打开或者关闭背光电源.通过设置LCDCON3寄存器的第28位来设置,从而实现对背光的切换操作.
if (iEsc == SETBACKLIGHT) { if (cjIn == sizeof(BOOL) && pvIn != NULL) { if (*(BOOL*)pvIn) { // Switch backlight on by clearing bit 28 m_s2410LCD->LCDCON3 &= 0xefffffff; } else { // Switch backlight off by setting bit 28 m_s2410LCD->LCDCON3 |= 0x10000000; } return 1; } return -1; } else if (iEsc == GETBACKLIGHT) { if (cjOut == sizeof(BOOL) && pvOut != NULL) { if (m_s2410LCD->LCDCON3 & 0x10000000) // Examine bit 28 - backlight { *(BOOL*)pvOut = FALSE; // bit is set: backlight is off } else { *(BOOL*)pvOut = TRUE; // bit is clear: backlight is on } return 1; } return -1; }
代码部分就分析到这里,并不复杂.驱动实际上会被应用程序或者Power Manager调用来进行背光电源管理.

6.注册表
在platform.reg中和BackLight相关的注册表项为:
IF BSP_NOBACKLIGHT !
[HKEY_LOCAL_MACHINE/Drivers/BuiltIn/Backlight]
    "Prefix"="BKL"
    "Dll"="backlight.dll"
    "Index"=dword:1
    "Order"=dword:1
    "IClass"="{A32942B7-920C-486b-B0E6-92A702A99B35}"

; Backlight tab of Display control panel (timeouts in seconds)
[HKEY_CURRENT_USER/ControlPanel/Backlight]
    "BatteryTimeout"=dword:3c ; 60 seconds
    "BacklightOnTap"=dword:1
    "ACTimeout"=dword:258 ; 600 seconds
    "ACBacklightOnTap"=dword:1
ENDIF BSP_NOBACKLIGHT !

其中 "IClass"="{A32942B7-920C-486b-B0E6-92A702A99B35}"这个GUID表示的是Generic power-manageable devices
这样PM就知道该驱动是支持电源管理的了,还有几个其他类型可以在common.reg中找到.
ControlPanel/Backlight中的设置只针对控制面板中的设置,这里的背光驱动并未实现这个功能.可以在驱动中创建线程等待事件的方式来实现.这个BackLight非常简单,只实现了一个基本框架,一个更复杂的例子可以参考PXA270的BSP(MAINSTONEIII).

7. 应用程序测试
新建一个SubProject,我们用SetDevicePower来设置背光状态,首先设置为D4(off),然后设置为D0(on).
int _tmain(int argc, TCHAR *argv[], TCHAR *envp[]) { SetDevicePower(TEXT("BKL1:"), POWER_NAME, D4); Sleep(3000); SetDevicePower(TEXT("BKL1:"), POWER_NAME, D0); Sleep(3000); _tprintf(_T("Hello World!/n")); return 0; }
这时可以看到KITL输出的从BackLight驱动和LCD驱动设置的打印信息:

不过WinCE建议用户尽量避免使用SetDevicePower该函数,改为使用SetPowerRequirement,由外设的驱动程序根据实际情况设置外设的设备电源状态.这里仅仅是测试驱动使用.