i2c: Remove i2c_algorithm.algo_control()

This removes:

- An effectively unused hook: i2c_algorithm.algo_control.

- The i2c_control() call, used only by i2c-dev to call that
unused hook or set two barely supported adapter params.

(That param setting moves into i2c-dev.c ... still iffy
due to lack of locking, but no other changes.)

As shown by diffstat, this is a net code shrink. It also reduces the
complexity of the I2C adapter and /dev interfaces.

Signed-off-by: David Brownell <[e-mail]>
Signed-off-by: Jean Delvare <[e-mail]>

drivers/i2c/i2c-core.c

···
 }
 EXPORT_SYMBOL(i2c_master_recv);
 
-int i2c_control(struct i2c_client *client,
-	unsigned int cmd, unsigned long arg)
-{
-	int ret = 0;
-	struct i2c_adapter *adap = client->adapter;
-
-	dev_dbg(&client->adapter->dev, "i2c ioctl, cmd: 0x%x, arg: %#lx\n", cmd, arg);
-	switch (cmd) {
-		case I2C_RETRIES:
-			adap->retries = arg;
-			break;
-		case I2C_TIMEOUT:
-			adap->timeout = arg;
-			break;
-		default:
-			if (adap->algo->algo_control!=NULL)
-				ret = adap->algo->algo_control(adap,cmd,arg);
-	}
-	return ret;
-}
-EXPORT_SYMBOL(i2c_control);
-
 /* ----------------------------------------------------
  * the i2c address scanning function
  * Will not work for 10-bit addresses!

drivers/i2c/i2c-dev.c

···
 				return -EFAULT;
 		}
 		return res;
-
+	case I2C_RETRIES:
+		client->adapter->retries = arg;
+		break;
+	case I2C_TIMEOUT:
+		client->adapter->timeout = arg;
+		break;
 	default:
-		return i2c_control(client,cmd,arg);
+		/* NOTE:  returning a fault code here could cause trouble
+		 * in buggy userspace code.  Some old kernel bugs returned
+		 * zero in this case, and userspace code might accidentally
+		 * have depended on that bug.
+		 */
+		return -ENOTTY;
 	}
 	return 0;
 }

include/linux/i2c.h

···
 	                   unsigned short flags, char read_write,
 	                   u8 command, int size, union i2c_smbus_data * data);
 
-	/* --- ioctl like call to set div. parameters. */
-	int (*algo_control)(struct i2c_adapter *, unsigned int, unsigned long);
-
 	/* To determine what the adapter supports */
 	u32 (*functionality) (struct i2c_adapter *);
 };
···
 extern int i2c_probe(struct i2c_adapter *adapter,
 		struct i2c_client_address_data *address_data,
 		int (*found_proc) (struct i2c_adapter *, int, int));
-
-/* An ioctl like call to set div. parameters of the adapter.
- */
-extern int i2c_control(struct i2c_client *,unsigned int, unsigned long);
 
 extern struct i2c_adapter* i2c_get_adapter(int id);
 extern void i2c_put_adapter(struct i2c_adapter *adap);