releases/4.14.73/spi-fix-idr-collision-on-systems-with-both-fixed-and-dynamic-spi-bus-numbers.patch

From 1a4327fbf4554d5b78d75b19a13d40d6de220159 Mon Sep 17 00:00:00 2001
From: Kirill Kapranov <kirill.kapranov@compulab.co.il>
Date: Mon, 13 Aug 2018 19:48:10 +0300
Subject: spi: fix IDR collision on systems with both fixed and dynamic SPI bus numbers

From: Kirill Kapranov <kirill.kapranov@compulab.co.il>

commit 1a4327fbf4554d5b78d75b19a13d40d6de220159 upstream.

On systems where some controllers get a dynamic ID assigned and some have
a fixed number (e.g. from ACPI tables), the current implementation might
run into an IDR collision: in case of a fixed bus number is gotten by a
driver (but not marked busy in IDR tree) and a driver with dynamic bus
number gets the same ID and predictably fails.

Fix this by means of checking-in fixed IDsin IDR as far as dynamic ones
at the moment of the controller registration.

Fixes: 9b61e302210e (spi: Pick spi bus number from Linux idr or spi alias)
Signed-off-by: Kirill Kapranov <kirill.kapranov@compulab.co.il>
Signed-off-by: Mark Brown <broonie@kernel.org>
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/spi/spi.c |    9 +++++++++
 1 file changed, 9 insertions(+)

--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -2135,6 +2135,15 @@ int spi_register_controller(struct spi_c
 		if (WARN(id < 0, "couldn't get idr"))
 			return id;
 		ctlr->bus_num = id;
+	} else {
+		/* 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;
 	}
 	INIT_LIST_HEAD(&ctlr->queue);
 	spin_lock_init(&ctlr->queue_lock);