Re: [PATCH] wireless-regdb: add DFS CAC time parameter

[Felix Fietkau <nbd@openwrt.org>]

On 2014-05-21 18:03, Johannes Berg wrote:
> On Tue, 2014-05-20 at 11:48 -0700, Luis R. Rodriguez wrote:
> 
>> > I think we should, but if we can't then at least can we cut to an
>> > extensible format?
> 
> I don't see any way to extend the format right now.
> 
> There's a wrinkle with making it more extensible too though - if we do
> that then we must be extremely careful that future older crda versions
> (i.e. the next version that we're about to write) will not parse a newer
> extended file more permissively, so our extensions are limited anyway.
> 
> Looks like the format update really is needed, which probably means we
> should change the scripts to generate two databases and change the
> filename, or so?
How about making the format properly extensible by reusing what we're
already doing to keep the kernel ABI stable? For example, we could store
the database in a netlink-like attribute format, with some changes to
make it fixed endian.
I'm already doing just that for a few things in OpenWrt, so I have
working C code for writing and parsing such a format.

Another nice feature would be to indicate in the attributes if crda is
required to understand them, or if it can just continue with a warning.

If done right, I think we can probably make this the last time we change
the format version.

- Felix