linux/3.8: backport 'spi/of: Use DT aliases for assigning bus number' from 3.9

Signed-off-by: Gabor Juhos <juhosg@openwrt.org>

SVN-Revision: 36328

target/linux/generic/patches-3.8/033-backport-spi-of-Use-DT-aliases-for-assigning-bus-number.patch

@@ -0,0 +1,37 @@
+From bb29785e0d6d150181704be2efcc3141044625e2 Mon Sep 17 00:00:00 2001
+From: Grant Likely <grant.likely@secretlab.ca>
+Date: Fri, 21 Dec 2012 19:32:09 +0000
+Subject: [PATCH] spi/of: Use DT aliases for assigning bus number
+
+Linux assigns a number to each spi_master in the system, but when the
+platform used the device tree, the numbers are dynamically assigned and
+are not predictable. In general this shouldn't matter since the kernel
+doesn't use the bus number for anything other than matching a bus to
+spi_boardinfo (not used for DT). However, sometimes userspace needs to
+figure out which bus is which, so it makes sense to use the global
+/aliases namespace to choose a specific bus number.
+
+It is safe to derive the bus number from an alias because aliases will
+never cause two buses to try and use the same bus number. (At one time
+the cell-index property was used for this purpose, but cell-index has
+the risk of an id collision).
+
+Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
+Cc: Anatolij Gustschin <agust@denx.de>
+Cc: Mark Brown <broonie@opensource.wolfsonmicro.com>
+---
+ drivers/spi/spi.c |    3 +++
+ 1 file changed, 3 insertions(+)
+
+--- a/drivers/spi/spi.c
++++ b/drivers/spi/spi.c
+@@ -1135,6 +1135,9 @@ int spi_register_master(struct spi_maste
+ 	if (master->num_chipselect == 0)
+ 		return -EINVAL;
+ 
++	if ((master->bus_num < 0) && master->dev.of_node)
++		master->bus_num = of_alias_get_id(master->dev.of_node, "spi");
++
+ 	/* convention:  dynamically assigned bus IDs count down from the max */
+ 	if (master->bus_num < 0) {
+ 		/* FIXME switch to an IDR based scheme, something like