configurable device (and other) tables in the kernel ?

[Robert Watson]

On Thu, 1 Feb 2007, Luigi Rizzo wrote:

>> 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')
>
> Surely it requires some form of rebuild of the kernel but there doesn't seem 
> to be any other way to possibly solve the problem...

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?

Robert N M Watson
Computer Laboratory
University of Cambridge