[media] lirc_zilog: Restore checks for existence of the IR_tx object

This reverts commit 8090232a and
adds an additional check for ir->tx == NULL.

The user may need us to handle an RX only unit.  Apparently
there are TV capture units in existence with Rx only wiring
and/or RX only firmware for the on-board Zilog Z8 IR unit.
Signed-off-by: Andy Walls <awalls@md.metrocast.net>
Signed-off-by: Jarod Wilson <jarod@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/staging/lirc/lirc_zilog.c

@@ -209,7 +209,8 @@ static int add_to_buf(struct IR *ir)
 				return -ENODATA;
 			}
 			schedule_timeout((100 * HZ + 999) / 1000);
-			ir->tx->need_boot = 1;
+			if (ir->tx != NULL)
+				ir->tx->need_boot = 1;
 
 			++failures;
 			mutex_unlock(&ir->ir_lock);
@@ -1032,9 +1033,10 @@ static long ioctl(struct file *filep, unsigned int cmd, unsigned long arg)
 	int result;
 	unsigned long mode, features = 0;
 
-	features |= LIRC_CAN_SEND_PULSE;
 	if (ir->rx != NULL)
 		features |= LIRC_CAN_REC_LIRCCODE;
+	if (ir->tx != NULL)
+		features |= LIRC_CAN_SEND_PULSE;
 
 	switch (cmd) {
 	case LIRC_GET_LENGTH:
@@ -1061,9 +1063,15 @@ static long ioctl(struct file *filep, unsigned int cmd, unsigned long arg)
 			result = -EINVAL;
 		break;
 	case LIRC_GET_SEND_MODE:
+		if (!(features&LIRC_CAN_SEND_MASK))
+			return -ENOSYS;
+
 		result = put_user(LIRC_MODE_PULSE, (unsigned long *) arg);
 		break;
 	case LIRC_SET_SEND_MODE:
+		if (!(features&LIRC_CAN_SEND_MASK))
+			return -ENOSYS;
+
 		result = get_user(mode, (unsigned long *) arg);
 		if (!result && mode != LIRC_MODE_PULSE)
 			return -EINVAL;
@@ -1242,8 +1250,10 @@ static int ir_remove(struct i2c_client *client)
 	}
 
 	/* Good-bye Tx */
-	i2c_set_clientdata(ir->tx->c, NULL);
-	kfree(ir->tx);
+	if (ir->tx != NULL) {
+		i2c_set_clientdata(ir->tx->c, NULL);
+		kfree(ir->tx);
+	}
 
 	/* Good-bye IR */
 	del_ir_device(ir);
@@ -1393,9 +1403,12 @@ static int ir_probe(struct i2c_client *client, const struct i2c_device_id *id)
 	 * after registering with lirc as otherwise hotplug seems to take
 	 * 10s to create the lirc device.
 	 */
-	ret = tx_init(ir->tx);
-	if (ret != 0)
-		goto out_unregister;
+	if (ir->tx != NULL) {
+		/* Special TX init */
+		ret = tx_init(ir->tx);
+		if (ret != 0)
+			goto out_unregister;
+	}
 
 	zilog_info("probe of IR %s on %s (i2c-%d) done. IR unit ready.\n",
 		   tx_probe ? "Tx" : "Rx", adap->name, adap->nr);