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authorAhmad Fatoum <a.fatoum@pengutronix.de>2020-11-10 16:34:29 +0100
committerSascha Hauer <s.hauer@pengutronix.de>2020-11-13 08:53:40 +0100
commit4fd3686373e842ac3e43b53ca5280b38e5a3d96b (patch)
tree05de1fe191d1fbf7f85d155a26541ea04dd28094
parentd0f535b6a60a32683336b834837840615d0891f8 (diff)
downloadbarebox-4fd3686373e842ac3e43b53ca5280b38e5a3d96b.tar.gz
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doc: add note about characters like hyphens in variable names
The mismatch between the allowed characters in shell variables and device parameters is a common pitfall, especially because device tree node names often have hyphens in them, which is disallowed by hush. While such variables can be read by the ${variable-example}, setting them is only possible with the setenv command. Reflect this in the documentation. Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de> Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
-rw-r--r--Documentation/user/driver-model.rst9
1 files changed, 8 insertions, 1 deletions
diff --git a/Documentation/user/driver-model.rst b/Documentation/user/driver-model.rst
index a0fd3e99b5..c543d6d9c4 100644
--- a/Documentation/user/driver-model.rst
+++ b/Documentation/user/driver-model.rst
@@ -88,7 +88,14 @@ The parameters can be used as shell variables:
.. code-block:: sh
eth0.ipaddr=192.168.23.15
- echo "my current ip is: $eth0.ipaddr"
+ echo "my current ip is: ${eth0.ipaddr}"
+
+.. note::
+
+ Hush shell syntax for defining and setting variables is the same, so
+ some characters such as hyphens are not allowed on the left hand side
+ of a shell variable assignment. :ref:`command_setenv`, if enabled,
+ can still be used to write such a variable though.
device variables may have a type, so assigning wrong values may fail: