Add VIDEO_GetVideoScanMode & fix the __ViInit loop (#144)

* fixes: make compiler not remove the while loop by adding empty asm line

* video : add VIDEO_GetVideoScanMode

gc/ogc/video.h

@@ -199,6 +199,14 @@ u32 VIDEO_HaveComponentCable(void);
 
 GXRModeObj * VIDEO_GetPreferredMode(GXRModeObj *mode);
 
+/*! 
+ * \fn u32 VIDEO_GetVideoScanMode(void)
+ * \brief Get video scan mode. This function returns 0 when interlaced, 1 when non interlaced and 2 when progressive
+ *
+ * \return 0 when interlaced, 1 when non interlaced and 2 when progressive
+ */
+u32 VIDEO_GetVideoScanMode(void);
+
 #ifdef __cplusplus
    }
 #endif /* __cplusplus */

libogc/video.c

@@ -2090,7 +2090,12 @@ static void __VIInit(u32 vimode)
 	//reset the interface
 	cnt = 0;
 	_viReg[1] = 0x02;
-	while(cnt<1000) cnt++;
+	while(cnt<1000) 
+	{
+		__asm__ __volatile__ ("" ::: "memory");
+		cnt++;
+	}
+
 	_viReg[1] = 0x00;
 
 	// now begin to setup the interface
@@ -2958,3 +2963,20 @@ u32 VIDEO_HaveComponentCable(void)
 {
 	return (_viReg[55]&0x01);
 }
+
+u32 VIDEO_GetVideoScanMode(void)
+{
+	u32 level;
+	u32 mode;
+
+	_CPU_ISR_Disable(level);
+
+	// Check Clock Select Register for progressive clock
+	if (_viReg[54] & 1)
+		mode = VI_PROGRESSIVE;
+	else
+		mode = (_viReg[1] >> 2 & 1) ? VI_NON_INTERLACE : VI_INTERLACE;
+
+	_CPU_ISR_Restore(level);
+	return mode;
+}