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