bootconfig: Syntax updates

Currently, bootconfig adds new value on the existing key to the tail of an array. But this looks a bit confusing because admin can rewrite original value in same config file easily.

This rejects following value re-definition.

key = value1
...
key = value2

You should rewrite value1 to value2 in this case.

Signed-off-by Masami Hiramatsu <[email protected]>

---
 Documentation/admin-guide/bootconfig.rst   |   11 ++++++++++-
 lib/bootconfig.c                           |   13 ++++++++-----
 tools/bootconfig/samples/bad-samekey.bconf |    6 ++++++
 3 files changed, 24 insertions(+), 6 deletions(-)
 create mode 100644 tools/bootconfig/samples/bad-samekey.bconf

Documentation/admin-guide/bootconfig.rst +0 -0

index dfeffa73dca3..9ee7650b7817 100644

Documentation/admin-guide/bootconfig.rst Or more shorter, written as following:: · line 68

Quoted 11 lines · Masami Hiramatsu

Documentation/admin-guide/bootconfig.rst +4 -1

@@ -62,7 +62,16 @@ Or more shorter, written as following::
 In both styles, same key words are automatically merged when parsing it
 at boot time. So you can append similar trees or key-values.
 
-Note that a sub-key and a value can not co-exist under a parent key.
+Same-key Values
+---------------
+
+It is prohibited that two or more values or arraies share a same-key.

I think (?): arrays

Quoted 8 lines

Documentation/admin-guide/bootconfig.rst +6 -0

+For example,::
+
+ foo = bar, baz
+ foo = qux  # !ERROR! we can not re-define same key
+
+Also, a sub-key and a value can not co-exist under a parent key.
 For example, following config is NOT allowed.::
 

Documentation/admin-guide/bootconfig.rst Or more shorter, written as following:: · line 77

Quoted 1 line

Documentation/admin-guide/bootconfig.rst +0 -0

  foo = value1

I'm pretty sure that the kernel command line allows someone to use
key=value1 ... key=value2
and the first setting is just overwritten with value2 (for most "key"s).

Am I wrong? and is this patch saying that bootconfig won't operate like that?

Hi Randy,

Quoted 30 lines · Randy Dunlap

Documentation/admin-guide/bootconfig.rst Or more shorter, written as following:: · line 68

Quoted 11 lines · Masami Hiramatsu

Documentation/admin-guide/bootconfig.rst +4 -1

@@ -62,7 +62,16 @@ Or more shorter, written as following::
 In both styles, same key words are automatically merged when parsing it
 at boot time. So you can append similar trees or key-values.
 
-Note that a sub-key and a value can not co-exist under a parent key.
+Same-key Values
+---------------
+
+It is prohibited that two or more values or arraies share a same-key.

I think (?): arrays

Documentation/admin-guide/bootconfig.rst Or more shorter, written as following:: · line 77

Quoted 9 lines

Documentation/admin-guide/bootconfig.rst +6 -0

+For example,::
+
+ foo = bar, baz
+ foo = qux  # !ERROR! we can not re-define same key
+
+Also, a sub-key and a value can not co-exist under a parent key.
 For example, following config is NOT allowed.::
 
  foo = value1

I'm pretty sure that the kernel command line allows someone to use
key=value1 ... key=value2
and the first setting is just overwritten with value2 (for most "key"s).

Quoted 1 line

Am I wrong? and is this patch saying that bootconfig won't operate like that?

I think so. Both are retained.
A typical example is "console=ttyS0 console=tty", to have the kernel output on both the serial and the graphical console.

Quoted 33 lines · On Sat, 22 Feb 2020 10:31:17 +0100 Geert Uytterhoeven <[email protected]>…

Hi Randy,

Quoted 30 lines · Randy Dunlap

Documentation/admin-guide/bootconfig.rst Or more shorter, written as following:: · line 68

Quoted 11 lines · Masami Hiramatsu

Documentation/admin-guide/bootconfig.rst +4 -1

@@ -62,7 +62,16 @@ Or more shorter, written as following::
 In both styles, same key words are automatically merged when parsing it
 at boot time. So you can append similar trees or key-values.
 
-Note that a sub-key and a value can not co-exist under a parent key.
+Same-key Values
+---------------
+
+It is prohibited that two or more values or arraies share a same-key.

I think (?): arrays

Documentation/admin-guide/bootconfig.rst Or more shorter, written as following:: · line 77

Quoted 9 lines

Documentation/admin-guide/bootconfig.rst +6 -0

+For example,::
+
+ foo = bar, baz
+ foo = qux  # !ERROR! we can not re-define same key
+
+Also, a sub-key and a value can not co-exist under a parent key.
 For example, following config is NOT allowed.::
 
  foo = value1

I'm pretty sure that the kernel command line allows someone to use
key=value1 ... key=value2
and the first setting is just overwritten with value2 (for most "key"s).

Quoted 5 lines

Quoted 1 line

Am I wrong? and is this patch saying that bootconfig won't operate like that?

I think so. Both are retained.
A typical example is "console=ttyS0 console=tty", to have the kernel output on both the serial and the graphical console.

Right, it actually depends on how the option is defined and its handler. If the option is defined with module_param*() macros, those will be overwritten.
But if it is defined with __setup() or early_param(), the handler function will be called repeatedly. Thus, overwrite or append or skip later one depends on the option handler.

I think the bootconfig is a bit different from legacy command line at this moment. The legacy command line can be modified by bootloader, whereas the bootconfig is a single text file which user can update each value. Of course bootloader will support the bootconfig to append some key-values in the future.
So I would like to introduce another "overwrite" operator (":=") and "assign default" operator ("?=") too. With those operators, the bootloader can just add their own key-value without decoding the current bootconfig.