spi: Drop duplicate IDR allocation code in spi_register_controller()

Refactor spi_register_controller() to drop duplicate IDR allocation.
Instead of if-else-if branching use two sequential if:s, which allows
to re-use the logic of IDR allocation in all cases.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20230710154932.68377-3-andriy.shevchenko@linux.intel.comSigned-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi.c

@@ -3081,6 +3081,20 @@ static int spi_controller_check_ops(struct spi_controller *ctlr)
 	return 0;
 }
 
+/* Allocate dynamic bus number using Linux idr */
+static int spi_controller_id_alloc(struct spi_controller *ctlr, int start, int end)
+{
+	int id;
+
+	mutex_lock(&board_lock);
+	id = idr_alloc(&spi_master_idr, ctlr, start, end, GFP_KERNEL);
+	mutex_unlock(&board_lock);
+	if (WARN(id < 0, "couldn't get idr"))
+		return id == -ENOSPC ? -EBUSY : id;
+	ctlr->bus_num = id;
+	return 0;
+}
+
 /**
  * spi_register_controller - register SPI master or slave controller
  * @ctlr: initialized master, originally from spi_alloc_master() or
@@ -3108,8 +3122,8 @@ int spi_register_controller(struct spi_controller *ctlr)
 {
 	struct device		*dev = ctlr->dev.parent;
 	struct boardinfo	*bi;
+	int			first_dynamic;
 	int			status;
-	int			id, first_dynamic;
 
 	if (!dev)
 		return -ENODEV;
@@ -3122,27 +3136,13 @@ int spi_register_controller(struct spi_controller *ctlr)
 	if (status)
 		return status;
 
+	if (ctlr->bus_num < 0)
+		ctlr->bus_num = of_alias_get_id(ctlr->dev.of_node, "spi");
 	if (ctlr->bus_num >= 0) {
 		/* Devices with a fixed bus num must check-in with the num */
-		mutex_lock(&board_lock);
-		id = idr_alloc(&spi_master_idr, ctlr, ctlr->bus_num,
-			ctlr->bus_num + 1, GFP_KERNEL);
-		mutex_unlock(&board_lock);
-		if (WARN(id < 0, "couldn't get idr"))
-			return id == -ENOSPC ? -EBUSY : id;
-		ctlr->bus_num = id;
-	} else {
-		/* Allocate dynamic bus number using Linux idr */
-		id = of_alias_get_id(ctlr->dev.of_node, "spi");
-		if (id >= 0) {
-			ctlr->bus_num = id;
-			mutex_lock(&board_lock);
-			id = idr_alloc(&spi_master_idr, ctlr, ctlr->bus_num,
-				       ctlr->bus_num + 1, GFP_KERNEL);
-			mutex_unlock(&board_lock);
-			if (WARN(id < 0, "couldn't get idr"))
-				return id == -ENOSPC ? -EBUSY : id;
-		}
+		status = spi_controller_id_alloc(ctlr, ctlr->bus_num, ctlr->bus_num + 1);
+		if (status)
+			return status;
 	}
 	if (ctlr->bus_num < 0) {
 		first_dynamic = of_alias_get_highest_id("spi");
@@ -3151,13 +3151,9 @@ int spi_register_controller(struct spi_controller *ctlr)
 		else
 			first_dynamic++;
 
-		mutex_lock(&board_lock);
-		id = idr_alloc(&spi_master_idr, ctlr, first_dynamic,
-			       0, GFP_KERNEL);
-		mutex_unlock(&board_lock);
-		if (WARN(id < 0, "couldn't get idr"))
-			return id;
-		ctlr->bus_num = id;
+		status = spi_controller_id_alloc(ctlr, first_dynamic, 0);
+		if (status)
+			return status;
 	}
 	ctlr->bus_lock_flag = 0;
 	init_completion(&ctlr->xfer_completion);