Re: configurable device (and other) tables in the kernel ?

On Thursday 01 February 2007 13:45, Luigi Rizzo wrote:
On Thu, Feb 01, 2007 at 11:02:06AM -0700, M. Warner Losh wrote:
...
: plain text files!
:
: too obvious to think of it :)
:
: but, where can i find an example of a piece of kernel code that can
: read from a file "safely" (i.e. say in the modevent handler or maybe
: at device probe time) ?
: Something like
:
: char *load_file_into_kernel_memody(filename, max_size, &error);
:
: I have looked at the kernel side of execve and kldload, they are not
: exactly straightforward (at least there are seveal indirections).
: Maybe there are other simpler ones ?

Look at the firmware routines. However, they won't work until / is
mounted, which is after all the device probing happens.

unfortunately firmare images are embedded in .ko files, so the loading
is done elsewhere - but ok, i can spend some time figuring out
what LINKER_LOAD_FILE() does and whether it is just plain loading
of the file in memory or more than that, whether it can be made to
work even with an unstructured file, and so on.

Re. the availability of / - one of the requirements i had written
was the ability to preload the table at compile time - that's the
easy part, in the end it is just some macro/scripting magic to embed
the initial table in the object.
Short of putting into the table some hooks to give control
to the console and ask the user to manually type in
the 'alias ID' you were referring to (in the good old times
maybe someone would have even conceived a 'please type
the full driver image in hex')

Why not do what firmware(9) does? You can take a table and turn it into a
module and then either load that via the loader or kldload it at runtime (or
use linker_reference_module(9) at runtime). Granted, I still think the
concept is not really a good idea, but I think firmware(9) is actually a good
model for this sort of thing.

--
John Baldwin
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  • Re: configurable device (and other) tables in the kernel ?
    ... I have looked at the kernel side of execve and kldload, ... unfortunately firmare images are embedded in .ko files, ... what LINKER_LOAD_FILEdoes and whether it is just plain loading ...
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    ... which is after all the device probing happens. ... :> unfortunately firmare images are embedded in .ko files, ... :> is done elsewhere - but ok, i can spend some time figuring out ... :> to the console and ask the user to manually type in ...
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