[PATCH] spi:fix IDR collision on systems with both fixed and dynamic SPI bus numbers

[Kirill Kapranov]

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.kapra...@compulab.co.il>
---
 drivers/spi/spi.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index ec395a6baf9c..97e303185d5b 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -2170,6 +2170,15 @@ int spi_register_controller(struct spi_controller *ctlr)
                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);
-- 
2.11.0