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List:       freewrt-developers
Subject:    Re: [FreeWRT-developers] config in nvram or seperate partition
From:       "Bitsum Technologies Support" <support () bitsum ! com>
Date:       2006-06-30 17:25:39
Message-ID: e62c6c2c0606301025y7be9a60aiba8c607a5db7e449 () mail ! gmail ! com
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I apologize if I'm jumping in and missing something, or repeating
what's already been stated.

As mentioned, I think that creating a common abstract configuration
interface that uses a device-dependent backing store (exposed through
another abstract interface) is the way to go here.

For instance (high level view, of course can be implemented entirely
by free functions):

Package X -> IConfiguration -> IDeviceDependentStore

All packages an other system components would invoke the common
IConfiguration interface, which would, amongst other things, determine
the platform currently running and use the appropriate
IDeviceDependentStore to actually store and retrieve configuration
items.

...........................

Now, for backing storage on the Boradcom routers specifically:
Although the CFE (amongst other things) does use NVRAM variables,
preventing a complete overhaul of the NVRAM to a proprietary storage,
it should be possible to do something like leave the first 8kb for
standard NVRAM variables and use the remianing 24kb for proprietary
storage. The nvram storage format, iirc, is simply an array of
null-terminated strings, with the terminating string having a length
of 0 (two NULLs terminate array).

In example:

NVRAM (in kb)
[0-7]:   Standard format
[8-31]:  Proprietary format

One could compress the data stored in the last 24kb and fit quite a
lot of configuration data there -- I think probably as much as anybody
needs. There'd need to be certain checks to make sure somehow the
standard NVRAM data never exceeds 8kb, but this shouldn't be a big
deal, and should be plenty of storage. One could even grow the
proprietary storage backwards from the end, always leaving the maximum
amount of room for standard NVRAM storage.

There are advantages and disadvantages to using the NVRAM though. One
obvious advantage is that this area will be preserved in a firmware
upgrade.

The beauty of abstracting things as shown above is that even for the
same platform, multiple types of stores can be developed and the user
(or developer) can pick the one that works the best in their
particular circumstances.

-- 
db90h
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