Message-Id: <1464107960-10775-1-git-send-email-christer@weinigel.se>
Date:	Tue, 24 May 2016 18:39:20 +0200
From:	Christer Weinigel <christer@...nigel.se>
To:	linux-kernel@...r.kernel.org, linux-spi@...r.kernel.org,
	devicetree@...r.kernel.org
Cc:	Christer Weinigel <christer@...nigel.se>,
	Mark Brown <broonie@...nel.org>
Subject: [PATCH] devicetree - document using aliases to set spi bus number.

Document how to use devicetree aliases to assign a stable
bus number to a spi bus.

Signed-off-by: Christer Weinigel <christer@...nigel.se>

---

Trivial documentation change.

Not having used devicetree that much it was surprisingly hard to
figure out how to assign a stable bus number to a spi bus.  Add a
simple example that shows how to do that.

Mark Cced as the SPI maintainer.  Or should trivial documentation
fixes like this be addressed to someone else?

  /Christer

 Documentation/devicetree/bindings/spi/spi-bus.txt | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/Documentation/devicetree/bindings/spi/spi-bus.txt b/Documentation/devicetree/bindings/spi/spi-bus.txt
index 42d5954..c35c4c2 100644
--- a/Documentation/devicetree/bindings/spi/spi-bus.txt
+++ b/Documentation/devicetree/bindings/spi/spi-bus.txt
@@ -94,3 +94,13 @@ SPI example for an MPC5200 SPI bus:
 			reg = <1>;
 		};
 	};
+
+Normally SPI buses are assigned dynamic bus numbers starting at 32766
+and counting downwards.  It is possible to assign the bus number
+statically using devicetee aliases.  For example, on the MPC5200 the
+"spi@f00" device above is connected to the "soc" bus.  To set its
+bus_num to 1 add an aliases entry like this:
+
+	aliases {
+		spi1 = "/soc/spi@f00";
+	};
-- 
1.9.1

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