Messages in this thread | | | Date | Sat, 22 Feb 2020 23:41:47 +0900 | From | Masami Hiramatsu <> | Subject | Re: [PATCH v3 1/2] bootconfig: Prohibit re-defining value on same key |
| |
On Sat, 22 Feb 2020 10:31:17 +0100 Geert Uytterhoeven <geert@linux-m68k.org> wrote:
> Hi Randy, > > On Sat, Feb 22, 2020 at 5:30 AM Randy Dunlap <rdunlap@infradead.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.
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.
Thank you,
-- Masami Hiramatsu <mhiramat@kernel.org>
| |