V4L/DVB (6855): xc2028: select DTV78 firmware if tuning 7MHz VHF / 8MHz UHF

It seems that the DTV78 firmware is intended for use in locations where
VHF channels have 7MHz bandwidth and UHF channels have 8MHz bandwidth.
If we switch to DTV78 firmware when we detect this condition, we can
avoid firmware reloads when switching between VHF and UHF transponders.

Place the state for this in the control structure so that card drivers
can hint to us to use DTV78 firmware from the first tuning attempt.
Signed-off-by: NChris Pascoe <c.pascoe@itee.uq.edu.au>
Signed-off-by: NMauro Carvalho Chehab <mchehab@infradead.org>

drivers/media/video/tuner-xc2028.c

@@ -998,20 +998,27 @@ static int xc2028_set_params(struct dvb_frontend *fe,
 		return -EINVAL;
 	}
 
-	/* FIXME:
-	  There are two Scodes that will never be selected:
-		DTV78 ZARLINK456, DTV78 DIBCOM52
-	  When it should opt for DTV78 instead of DTV7 or DTV8?
-	*/
 	switch (bw) {
 	case BANDWIDTH_8_MHZ:
-		type |= DTV8 | F8MHZ;
+		if (p->frequency < 470000000)
+			priv->ctrl.vhfbw7 = 0;
+		else
+			priv->ctrl.uhfbw8 = 1;
+		type |= (priv->ctrl.vhfbw7 && priv->ctrl.uhfbw8) ? DTV78 : DTV8;
+		type |= F8MHZ;
 		break;
 	case BANDWIDTH_7_MHZ:
-		type |= DTV7 | F8MHZ;
+		if (p->frequency < 470000000)
+			priv->ctrl.vhfbw7 = 1;
+		else
+			priv->ctrl.uhfbw8 = 0;
+		type |= (priv->ctrl.vhfbw7 && priv->ctrl.uhfbw8) ? DTV78 : DTV7;
+		type |= F8MHZ;
 		break;
 	case BANDWIDTH_6_MHZ:
-		type |= DTV6 ;
+		type |= DTV6;
+		priv->ctrl.vhfbw7 = 0;
+		priv->ctrl.uhfbw8 = 0;
 		break;
 	default:
 		tuner_err("error: bandwidth not supported.\n");

drivers/media/video/tuner-xc2028.h

@@ -30,6 +30,8 @@ struct xc2028_ctrl {
 	unsigned int		mts   :1;
 	unsigned int		d2633 :1;
 	unsigned int		input1:1;
+	unsigned int		vhfbw7:1;
+	unsigned int		uhfbw8:1;
 	unsigned int		demod;
 };