[PATCH 3/3] Documentation: bootconfig: Add bootconfig override operator

From: Masami Hiramatsu <mhiramat@kernel.org>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Alistair Delva <adelva@google.com>,
	mhiramat@kernel.org, linux-doc@vger.kernel.org,
	LKML <linux-kernel@vger.kernel.org>
Subject: [PATCH 3/3] Documentation: bootconfig: Add bootconfig override operator
Date: Thu, 16 Jul 2020 01:00:47 +0900	[thread overview]
Message-ID: <159482884682.126704.7198860675721719878.stgit@devnote2> (raw)
In-Reply-To: <159482882056.126704.15508672095852220119.stgit@devnote2>

Add a sentence about bootconfig override operator (":=") to
bootconfig.rst.

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
---
 Documentation/admin-guide/bootconfig.rst |   11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/Documentation/admin-guide/bootconfig.rst b/Documentation/admin-guide/bootconfig.rst
index d6b3b77a4129..a22024f9175e 100644
--- a/Documentation/admin-guide/bootconfig.rst
+++ b/Documentation/admin-guide/bootconfig.rst
@@ -71,6 +71,16 @@ For example,::
  foo = bar, baz
  foo = qux  # !ERROR! we can not re-define same key
 
+If you want to update the value, you must use the override operator
+``:=`` explicitly. For example::
+
+ foo = bar, baz
+ foo := qux
+
+then, the ``qux`` is assigned to ``foo`` key. This is useful for
+overriding the default value by adding (partial) custom bootconfigs
+without parsing the default bootconfig.
+
 If you want to append the value to existing key as an array member,
 you can use ``+=`` operator. For example::
 
@@ -84,6 +94,7 @@ For example, following config is NOT allowed.::
 
  foo = value1
  foo.bar = value2 # !ERROR! subkey "bar" and value "value1" can NOT co-exist
+ foo.bar := value2 # !ERROR! even with the override operator, this is NOT allowed.
 
 
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