Date: Sat, 3 Feb 2007 04:32:50 -0800 From: Luigi Rizzo <rizzo@icir.org> To: Robert Watson <rwatson@FreeBSD.org> Cc: freebsd-arch@FreeBSD.org Subject: Re: configurable device (and other) tables in the kernel ? Message-ID: <20070203043250.A8294@xorpc.icir.org> In-Reply-To: <20070203115235.W91177@fledge.watson.org>; from rwatson@FreeBSD.org on Sat, Feb 03, 2007 at 11:55:03AM %2B0000 References: <20070131115148.A60420@xorpc.icir.org> <200702011109.12821.jhb@freebsd.org> <20070201.110206.1102529050.imp@bsdimp.com> <20070201104506.B82313@xorpc.icir.org> <20070203115235.W91177@fledge.watson.org>
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On Sat, Feb 03, 2007 at 11:55:03AM +0000, Robert Watson wrote:
...
> The preferred way to make configuration frobs available during early boot is
> via the hints mechanism, which supports both loading data via the loader,
> compiling it into the kernel, and updating it using kenv(8). I'd really like
> us avoid adding yet more file access dependencies in the kernel. These tend
> to be fragile, can only run in certain contexts, run into issues with changing
> roots, etc. Could we add /boot/deviceids.hints to match /boot/device.hints?
ok i was just asking for what the available options are.
But in another private email i was mentioning that the bootloader
"load" mechanism also already support loading opaque files
and seems to pass the info to the kernel (preloaded_files ?),
and this would overcome what i think is a limitation of the hints/kenv
mechanism (more below).
Following your principle (which i agree with) there would be no reason to
have a separate the firmware(9) mechanism except that:
+ the hints/kenv/loader variables/resource mechanism has too many
different names so people get confused on what it really is or can do;
+ documentation is also lacking a lot. E.g. "man -k hints" does not
mention kenv(2), which in turn does not mention any of the
resource_*(9) calls ("man -k resource" lists a few but not all
of them, but you have to know in the first place that 'resource'
and 'hint' are related, see previous point).
+ it seems to me that hints are only good at storing C strings i.e.
single lines of plain text. There is no support for opaque binary
data files.
+ the internal organization of hints is just a single list. Even if
one forgets about binary data and tries to store some large tables
(device ids, quirks etc) as multiple one-line name=value entries,
the mechanism doesn't scale.
All of the above can be fixed - especially the documentation part,
but that doesn't mean that the hints mechanism can already do
what i was asking; there is still a bit of work to do...
cheers
luigi
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