[PATCH 2/7] spi: support dynamic bus ids

[Sascha Hauer]

When probing spi bus masters from devicetree they got a bus_num
of -1. This works with a single bus master only since all bus masters
had the same bus_num. Detect this and dynamically assign a valid
bus_num.

Signed-off-by: Sascha Hauer <s.hauer at pengutronix.de>
---
 drivers/spi/spi.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index d273050..f035cc2 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -214,6 +214,7 @@ static LIST_HEAD(spi_master_list);
  */
 int spi_register_master(struct spi_master *master)
 {
+	static int dyn_bus_id = (1 << 15) - 1;
 	int			status = -ENODEV;
 
 	debug("%s: %s:%d\n", __func__, master->dev->name, master->dev->id);
@@ -224,6 +225,10 @@ int spi_register_master(struct spi_master *master)
 	if (master->num_chipselect == 0)
 		return -EINVAL;
 
+	/* convention:  dynamically assigned bus IDs count down from the max */
+	if (master->bus_num < 0)
+		master->bus_num = dyn_bus_id--;
+
 	list_add_tail(&master->list, &spi_master_list);
 
 	spi_of_register_slaves(master);
-- 
1.8.4.rc3