bootconfig: Terminate value search if it hits a newline

Terminate the value search for a key if it hits a newline and make
the value empty.

When we pass a bootconfig with an empty value terminated by the
newline, like below::

  foo =
  bar = value

Current bootconfig interprets it as a single entry::

  foo = "bar = value";

The Documentation/admin-guide/bootconfig.rst defines the value
itself is terminated by newline:

  The value has to be terminated by semi-colon (``;``) or newline (``\n``).

but it does not define when the value search is terminated.
This changes the behavior to be more line-oriented, so that it is
clearer in how it works.

- The value search of key-value pair will be terminated by a comment
  or newline.
- The value search of an array will continue beyond comments and
  newlines.

Thus, with this update, the above example is interpreted as::

  foo = "";
  bar = "value";

And the below example will cause a syntax error because "bar" is expected
as a key but it has ','.

  foo =
    bar, buz

According to this change, one wrong example config is updated.

Link: https://lore.kernel.org/all/177025238503.14982.17059549076175612447.stgit@devnote2/

Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Reviewed-by: Julius Werner <jwerner@chromium.org>

1 files changed, 16 insertions, 8 deletions

diff --git a/Documentation/admin-guide/bootconfig.rst b/Documentation/admin-guide/bootconfig.rst
index 7a86042c9b6d..f712758472d5 100644
--- a/Documentation/admin-guide/bootconfig.rst
+++ b/Documentation/admin-guide/bootconfig.rst
@@ -20,18 +20,26 @@ Config File Syntax
 
 The boot config syntax is a simple structured key-value. Each key consists
 of dot-connected-words, and key and value are connected by ``=``. The value
-has to be terminated by semi-colon (``;``) or newline (``\n``).
-For array value, array entries are separated by comma (``,``). ::
-
-  KEY[.WORD[...]] = VALUE[, VALUE2[...]][;]
-
-Unlike the kernel command line syntax, spaces are OK around the comma and ``=``.
+string has to be terminated by the following delimiters described below.
 
 Each key word must contain only alphabets, numbers, dash (``-``) or underscore
 (``_``). And each value only contains printable characters or spaces except
 for delimiters such as semi-colon (``;``), new-line (``\n``), comma (``,``),
 hash (``#``) and closing brace (``}``).
 
+If the ``=`` is followed by whitespace up to one of these delimiters, the
+key is assigned an empty value.
+
+For arrays, the array values are comma (``,``) separated, and comments and
+line breaks with newline (``\n``) are allowed between array values for
+readability. Thus the first entry of the array must be on the same line as
+the key.::
+
+  KEY[.WORD[...]] = VALUE[, VALUE2[...]][;]
+
+Unlike the kernel command line syntax, white spaces (including tabs) are
+ignored around the comma and ``=``.
+
 If you want to use those delimiters in a value, you can use either double-
 quotes (``"VALUE"``) or single-quotes (``'VALUE'``) to quote it. Note that
 you can not escape these quotes.
@@ -138,8 +146,8 @@ This is parsed as below::
  foo = value
  bar = 1, 2, 3
 
-Note that you can not put a comment between value and delimiter(``,`` or
-``;``). This means following config has a syntax error ::
+Note that you can NOT put a comment or a newline between value and delimiter
+(``,`` or ``;``). This means following config has a syntax error ::
 
  key = 1 # comment
        ,2