[media] vivid-tpg: correctly average the two pixels in gen_twopix()

gen_twopix() is always called twice: once for the first and once for
the second pixel. Improve the code to properly average the two if the
format requires horizontal downsampling.

This is necessary for patterns like 1x1 red/blue checkers.
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>

drivers/media/platform/vivid/vivid-tpg.c

@@ -687,28 +687,64 @@ static void gen_twopix(struct tpg_data *tpg,
 	switch (tpg->fourcc) {
 	case V4L2_PIX_FMT_NV16M:
 		buf[0][offset] = r_y;
-		buf[1][offset] = odd ? b_v : g_u;
+		if (odd) {
+			buf[1][0] = (buf[1][0] + g_u) / 2;
+			buf[1][1] = (buf[1][1] + b_v) / 2;
+			break;
+		}
+		buf[1][0] = g_u;
+		buf[1][1] = b_v;
 		break;
 	case V4L2_PIX_FMT_NV61M:
 		buf[0][offset] = r_y;
-		buf[1][offset] = odd ? g_u : b_v;
+		if (odd) {
+			buf[1][0] = (buf[1][0] + b_v) / 2;
+			buf[1][1] = (buf[1][1] + g_u) / 2;
+			break;
+		}
+		buf[1][0] = b_v;
+		buf[1][1] = g_u;
 		break;
 
 	case V4L2_PIX_FMT_YUYV:
 		buf[0][offset] = r_y;
-		buf[0][offset + 1] = odd ? b_v : g_u;
+		if (odd) {
+			buf[0][1] = (buf[0][1] + g_u) / 2;
+			buf[0][3] = (buf[0][3] + b_v) / 2;
+			break;
+		}
+		buf[0][1] = g_u;
+		buf[0][3] = b_v;
 		break;
 	case V4L2_PIX_FMT_UYVY:
-		buf[0][offset] = odd ? b_v : g_u;
 		buf[0][offset + 1] = r_y;
+		if (odd) {
+			buf[0][0] = (buf[0][0] + g_u) / 2;
+			buf[0][2] = (buf[0][2] + b_v) / 2;
+			break;
+		}
+		buf[0][0] = g_u;
+		buf[0][2] = b_v;
 		break;
 	case V4L2_PIX_FMT_YVYU:
 		buf[0][offset] = r_y;
-		buf[0][offset + 1] = odd ? g_u : b_v;
+		if (odd) {
+			buf[0][1] = (buf[0][1] + b_v) / 2;
+			buf[0][3] = (buf[0][3] + g_u) / 2;
+			break;
+		}
+		buf[0][1] = b_v;
+		buf[0][3] = g_u;
 		break;
 	case V4L2_PIX_FMT_VYUY:
-		buf[0][offset] = odd ? g_u : b_v;
 		buf[0][offset + 1] = r_y;
+		if (odd) {
+			buf[0][0] = (buf[0][0] + b_v) / 2;
+			buf[0][2] = (buf[0][2] + g_u) / 2;
+			break;
+		}
+		buf[0][0] = b_v;
+		buf[0][2] = g_u;
 		break;
 	case V4L2_PIX_FMT_RGB565:
 		buf[0][offset] = (g_u << 5) | b_v;