[U-Boot] U-Boot and The Boot Loader Specification

[Dennis Gilmore]

El vie, 19-10-2018 a las 12:12 +0200, Wolfgang Denk escribió:
> Dear Alexander,
> 
> In message <118460556.a0Y5euKZZ7 at ada> you wrote:
> > >  864 /*
> > >  865  * Keywords recognized.
> > >  866  */
> > >  867 static const struct token keywords[] = {
> > >  868         {"menu", T_MENU},
> > >  869         {"title", T_TITLE},
> > >  870         {"timeout", T_TIMEOUT},
> > >  871         {"default", T_DEFAULT},
> > >  872         {"prompt", T_PROMPT},
> > >  873         {"label", T_LABEL},
> > >  874         {"kernel", T_KERNEL},
> > >  875         {"linux", T_LINUX},
> > >  876         {"localboot", T_LOCALBOOT},
> > >  877         {"append", T_APPEND},
> > >  878         {"initrd", T_INITRD},
> > >  879         {"include", T_INCLUDE},
> > >  880         {"devicetree", T_FDT},
> > >  881         {"fdt", T_FDT},
> > >  882         {"devicetreedir", T_FDTDIR},
> > >  883         {"fdtdir", T_FDTDIR},
> > >  884         {"ontimeout", T_ONTIMEOUT,},
> > >  885         {"ipappend", T_IPAPPEND,},
> > >  886         {NULL, T_INVALID}
> > >  887 };
> > > 
> > > This does not fit with your description, as you list:
> > > > 	Ignoring unknown command: title
> > > > 	Ignoring unknown command: version
> > > > 	Ignoring unknown command: options
> > > > 	Ignoring unknown command: linux
> > > > 	Ignoring unknown command: devicetree
> > > 
> > > OK, "version" and "options" are not implemented, but the other
> > > keywords are, so you must be doing something else wrong.
> > 
> > That's what I was saying. I suppose the handling of label and title
> > is 
> > different, so the entry group I had below 'title' was not
> > recognized as group 
> > of options for one entry, like it was when replacing title with
> > label. I can 
> > write an actually working extlinux.conf file (as showed in my last
> > mail), but 
> > that was not the question I had in the first place.
> 
> Well, what confuses me here is that you cleanly show error messages
> for example for title, linux, and devicetree, even though these
> should be recognized as valid keywords.
> 
> I think there are sublte imcompatibilities in your config file
> (and/or bugs in the code).  See also this comment (same file):
> 
>  440  * A note on the pxe file parser.
>  441  *
>  442  * We're parsing files that use syslinux grammar, which has a
> few quirks.
>  443  * String literals must be recognized based on context - there
> is no
>  444  * quoting or escaping support. There's also nothing to
> explicitly indicate
>  445  * when a label section completes. We deal with that by ending a
> label
>  446  * section whenever we see a line that doesn't include.
>  447  *
>  448  * As with the syslinux family, this same file format could be
> reused in the
>  449  * future for non pxe purposes. The only action it takes during
> parsing that
>  450  * would throw this off is handling of include files. It assumes
> we're using
>  451  * pxe, and does a tftp download of a file listed as an include
> file in the
>  452  * middle of the parsing operation. That could be handled by
> refactoring it to
>  453  * take a 'include file getter' function.
> 
> > The U-Boot documentation in the file 'doc/README.distro' could lead
> > to the 
> > impression as if U-Boot would support the BootLoaderSpec and even
> > links to it: 
> > http://www.freedesktop.org/wiki/Specifications/BootLoaderSpec/
> > 
> > That spec says basically, in my own words: "put one conf file for
> > each boot 
> > menu item in the directory /boot/loader/entries and let it have the
> > following 
> > format." 
> > 
> > The keywords differ from the ones used by extlinux/U-Boot, in my
> > opinion the 
> > U-Boot documentation in 'doc/README.distro' however is not very
> > clear about 
> > that.
> 
> I'm adding Dennis on Cc: who submitted the doc; I hope he has a
> better understanding of the state of things.

Sorry for the slow response, I have been travelling,  currently u-boot
does not support the boot loader spec, it was a goal that no-one found
the time to solve, the main issue being how to we traverse the
directories to parse all the snippets.

> > Is U-Boot supposed to honour that Boot Loader Specification?
> 
> I think it should, if possible.
> 
> > If yes: then it does not work as specified. Is anybody working on
> > making U-
> > Boot comply?
> 
> None that I know of.
There is no one working on it, I should remove the link to
BootLoaderSpec 

> > If no: would anybody mind changing the documentation to better
> > reflect what U-
> > Boot actually does and not mislead people into thinking U-Boot
> > would be 
> > compliant to that specification (like it was the case for me)? I
> > would send a 
> > patch if nobody objects.
> 
> Can we not do it the other way round, and fix the code that it
> improves and conforms (better) to the spec?

We could, I have not yet found a way to solve the problems. It would be
nice to solve them

Dennis
> Best regards,
> 
> Wolfgang Denk
>