i2c-algo-bit: Add pre- and post-xfer hooks

Drivers might have to do random things before and/or after I2C
transfers. Add hooks to the i2c-algo-bit implementation to let them do
so.
Signed-off-by: Jean Delvare <khali@linux-fr.org>
Cc: Alex Deucher <alexdeucher@gmail.com>

drivers/i2c/algos/i2c-algo-bit.c

@@ -522,6 +522,12 @@ static int bit_xfer(struct i2c_adapter *i2c_adap,
 	int i, ret;
 	unsigned short nak_ok;
 
+	if (adap->pre_xfer) {
+		ret = adap->pre_xfer(i2c_adap);
+		if (ret < 0)
+			return ret;
+	}
+
 	bit_dbg(3, &i2c_adap->dev, "emitting start condition\n");
 	i2c_start(adap);
 	for (i = 0; i < num; i++) {
@@ -570,6 +576,9 @@ static int bit_xfer(struct i2c_adapter *i2c_adap,
 bailout:
 	bit_dbg(3, &i2c_adap->dev, "emitting stop condition\n");
 	i2c_stop(adap);
+
+	if (adap->post_xfer)
+		adap->post_xfer(i2c_adap);
 	return ret;
 }
 

include/linux/i2c-algo-bit.h

@@ -36,6 +36,8 @@ struct i2c_algo_bit_data {
 	void (*setscl) (void *data, int state);
 	int  (*getsda) (void *data);
 	int  (*getscl) (void *data);
+	int  (*pre_xfer)  (struct i2c_adapter *);
+	void (*post_xfer) (struct i2c_adapter *);
 
 	/* local settings */
 	int udelay;		/* half clock cycle time in us,