i2c-algo-pcf: Add adapter hooks around xfer begin and end

Some I2C bus implementations need to synchronize with external
entities, such as system firmware, which might also be programming the
same I2C bus.

In order to facilitate this add ->xfer_begin() and ->xfer_end() hooks
which are invoked around pcf_xfer().

[JD: Make these hooks optional.]

Signed-off-by: David S. Miller <[e-mail]>
Signed-off-by: Jean Delvare <[e-mail]>

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

···
 	int i;
 	int ret=0, timeout, status;
     
+	if (adap->xfer_begin)
+		adap->xfer_begin(adap->data);
 
 	/* Check for bus busy */
 	timeout = wait_for_bb(adap);
 	if (timeout) {
 		DEB2(printk(KERN_ERR "i2c-algo-pcf.o: "
 		            "Timeout waiting for BB in pcf_xfer\n");)
-		return -EIO;
+		i = -EIO;
+		goto out;
 	}
 	
 	for (i = 0;ret >= 0 && i < num; i++) {
···
 		if (timeout) {
 			if (timeout == -EINTR) {
 				/* arbitration lost */
-				return (-EINTR);
+				i = -EINTR;
+				goto out;
 			}
 			i2c_stop(adap);
 			DEB2(printk(KERN_ERR "i2c-algo-pcf.o: Timeout waiting "
 				    "for PIN(1) in pcf_xfer\n");)
-			return (-EREMOTEIO);
+			i = -EREMOTEIO;
+			goto out;
 		}
     
 #ifndef STUB_I2C
···
 		if (status & I2C_PCF_LRB) {
 			i2c_stop(adap);
 			DEB2(printk(KERN_ERR "i2c-algo-pcf.o: No LRB(1) in pcf_xfer\n");)
-			return (-EREMOTEIO);
+			i = -EREMOTEIO;
+			goto out;
 		}
 #endif
     
···
 		}
 	}
 
+out:
+	if (adap->xfer_end)
+		adap->xfer_end(adap->data);
 	return (i);
 }
 

include/linux/i2c-algo-pcf.h

···
 	int  (*getclock) (void *data);
 	void (*waitforpin) (void *data);
 
+	void (*xfer_begin) (void *data);
+	void (*xfer_end) (void *data);
+
 	/* Multi-master lost arbitration back-off delay (msecs)
 	 * This should be set by the bus adapter or knowledgable client
 	 * if bus is multi-mastered, else zero