[media] gspca/sn9c20x: Test if sensor is a OV sensor

Instead of just assuming a ov9650 sensor based on USB ID,
double-check it, by reading the sensor ID.
Acked-by: Jean-Francois Moine <moinejf@free.fr>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/video/gspca/sn9c20x.c

@@ -1224,8 +1224,17 @@ static int i2c_r2(struct gspca_dev *gspca_dev, u8 reg, u16 *val)
 static int ov9650_init_sensor(struct gspca_dev *gspca_dev)
 {
 	int i;
+	u16 id;
 	struct sd *sd = (struct sd *) gspca_dev;
 
+	if (i2c_r2(gspca_dev, 0x1c, &id) < 0)
+		return -EINVAL;
+
+	if (id != 0x7fa2) {
+		err("sensor id for ov9650 doesn't match (0x%04x)", id);
+		return -ENODEV;
+	}
+
 	for (i = 0; i < ARRAY_SIZE(ov9650_init); i++) {
 		if (i2c_w1(gspca_dev, ov9650_init[i].reg,
 				ov9650_init[i].val) < 0) {