media: dw2102: probe for demodulator i2c address

This is required to support the Terratec S2 USB Box Revision 4, which
reused usb vid:pid, but has a different demodulator (m88ds3103b) at
i2c address 0x6a.

[fixed checkpatch issues]
Signed-off-by: Michael Bunk <micha@freedict.org>
Signed-off-by: Brad Love <brad@nextdimension.cc>
Signed-off-by: Sean Young <sean@mess.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

drivers/media/usb/dvb-usb/dw2102.c

@@ -1524,6 +1524,29 @@ static int m88rs2000_frontend_attach(struct dvb_usb_adapter *adap)
 	return -EIO;
 }
 
+static int tt_s2_4600_frontend_attach_probe_demod(struct dvb_usb_device *d,
+						  const int probe_addr)
+{
+	struct dw2102_state *state = d->priv;
+
+	state->data[0] = 0x9;
+	state->data[1] = 0x1;
+	state->data[2] = 0x1;
+	state->data[3] = probe_addr;
+	state->data[4] = 0x0;
+
+	if (dvb_usb_generic_rw(d, state->data, 5, state->data, 2, 0) < 0) {
+		err("i2c probe for address 0x%x failed.", probe_addr);
+		return 0;
+	}
+
+	if (state->data[0] != 8) /* fail(7) or error, no device at address */
+		return 0;
+
+	/* probing successful */
+	return 1;
+}
+
 static int tt_s2_4600_frontend_attach(struct dvb_usb_adapter *adap)
 {
 	struct dvb_usb_device *d = adap->dev;
@@ -1533,6 +1556,7 @@ static int tt_s2_4600_frontend_attach(struct dvb_usb_adapter *adap)
 	struct i2c_board_info board_info;
 	struct m88ds3103_platform_data m88ds3103_pdata = {};
 	struct ts2020_config ts2020_config = {};
+	int demod_addr;
 
 	mutex_lock(&d->data_mutex);
 
@@ -1570,8 +1594,22 @@ static int tt_s2_4600_frontend_attach(struct dvb_usb_adapter *adap)
 	if (dvb_usb_generic_rw(d, state->data, 1, state->data, 1, 0) < 0)
 		err("command 0x51 transfer failed.");
 
+	/* probe for demodulator i2c address */
+	demod_addr = -1;
+	if (tt_s2_4600_frontend_attach_probe_demod(d, 0x68))
+		demod_addr = 0x68;
+	else if (tt_s2_4600_frontend_attach_probe_demod(d, 0x69))
+		demod_addr = 0x69;
+	else if (tt_s2_4600_frontend_attach_probe_demod(d, 0x6a))
+		demod_addr = 0x6a;
+
 	mutex_unlock(&d->data_mutex);
 
+	if (demod_addr < 0) {
+		err("probing for demodulator failed. Is the external power switched on?");
+		return -ENODEV;
+	}
+
 	/* attach demod */
 	m88ds3103_pdata.clk = 27000000;
 	m88ds3103_pdata.i2c_wr_max = 33;
@@ -1586,8 +1624,11 @@ static int tt_s2_4600_frontend_attach(struct dvb_usb_adapter *adap)
 	m88ds3103_pdata.lnb_hv_pol = 1;
 	m88ds3103_pdata.lnb_en_pol = 0;
 	memset(&board_info, 0, sizeof(board_info));
-	strscpy(board_info.type, "m88ds3103", I2C_NAME_SIZE);
-	board_info.addr = 0x68;
+	if (demod_addr == 0x6a)
+		strscpy(board_info.type, "m88ds3103b", I2C_NAME_SIZE);
+	else
+		strscpy(board_info.type, "m88ds3103", I2C_NAME_SIZE);
+	board_info.addr = demod_addr;
 	board_info.platform_data = &m88ds3103_pdata;
 	request_module("m88ds3103");
 	client = i2c_new_client_device(&d->i2c_adap, &board_info);