linux-kernel - Re: [PATCH v3 1/2] bootconfig: Prohibit re-defining value on same key

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Date:   Sat, 22 Feb 2020 10:31:17 +0100
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Randy Dunlap <rdunlap@...radead.org>
Cc:     Masami Hiramatsu <mhiramat@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Borislav Petkov <bp@...en8.de>,
        LKML <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH v3 1/2] bootconfig: Prohibit re-defining value on same key

Hi Randy,

On Sat, Feb 22, 2020 at 5:30 AM Randy Dunlap <rdunlap@...radead.org> wrote:
> On 2/21/20 12:13 AM, Masami Hiramatsu wrote:
> > --- a/Documentation/admin-guide/bootconfig.rst
> > +++ b/Documentation/admin-guide/bootconfig.rst
> > @@ -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
>
> > +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).
>
> 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.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds