media: dvb-frontends/tc90522: extend i2c algo to support some devices

This demod implements an i2c adapter for attached tuner
and relays i2c messages from users (dvb adapters / bridge chips).
Some of them, such as Friio dvb card using gl861,
require each pair of i2c messages for one read to be issued as
two separate transactions.
This patch adds a configuration option to enable this split.
Signed-off-by: Akihiro Tsukada <tskd08@gmail.com>
Signed-off-by: Sean Young <sean@mess.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>

drivers/media/dvb-frontends/tc90522.c

@@ -685,10 +685,33 @@ tc90522_master_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
 		p += new_msgs[j].len;
 	}
 
-	if (i < num)
+	if (i < num) {
 		ret = -ENOMEM;
-	else
+	} else if (!state->cfg.split_tuner_read_i2c || rd_num == 0) {
 		ret = i2c_transfer(state->i2c_client->adapter, new_msgs, j);
+	} else {
+		/*
+		 * Split transactions at each I2C_M_RD message.
+		 * Some of the parent device require this,
+		 * such as Friio (see. dvb-usb-gl861).
+		 */
+		int from, to;
+
+		ret = 0;
+		from = 0;
+		do {
+			int r;
+
+			to = from + 1;
+			while (to < j && !(new_msgs[to].flags & I2C_M_RD))
+				to++;
+			r = i2c_transfer(state->i2c_client->adapter,
+					 &new_msgs[from], to - from);
+			ret = (r <= 0) ? r : ret + r;
+			from = to;
+		} while (from < j && ret > 0);
+	}
+
 	if (ret >= 0 && ret < j)
 		ret = -EIO;
 	kfree(new_msgs);

drivers/media/dvb-frontends/tc90522.h

@@ -28,6 +28,9 @@ struct tc90522_config {
 
 	/* [OUT] tuner I2C adapter returned by driver */
 	struct i2c_adapter *tuner_i2c;
+
+	/* [IN] use two separate I2C transactions for one tuner read */
+	bool split_tuner_read_i2c;
 };
 
 #endif /* TC90522_H */