From bb29785e0d6d150181704be2efcc3141044625e2 Mon Sep 17 00:00:00 2001 From: Grant Likely 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 Cc: Anatolij Gustschin Cc: Mark Brown --- 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