Re: [PATCH] cfg80211: warn if db.txt is empty with CONFIG_CFG80211_INTERNAL_REGDB

["John W. Linville" <linville@tuxdriver.com>]

On Tue, Mar 20, 2012 at 12:13:34AM -0700, Luis R. Rodriguez wrote:
> On Tue, Mar 20, 2012 at 12:08 AM, Johannes Berg
> <johannes@sipsolutions.net> wrote:
> > On Tue, 2012-03-20 at 00:00 -0700, Luis R. Rodriguez wrote:
> >
> >> >>  net/wireless/reg.c |   12 ++++++++++++
> >> >>  1 file changed, 12 insertions(+)
> >> >>
> >> >> diff --git a/net/wireless/reg.c b/net/wireless/reg.c
> >> >> index e9a0ac8..85f51b3 100644
> >> >> --- a/net/wireless/reg.c
> >> >> +++ b/net/wireless/reg.c
> >> >> @@ -388,7 +388,18 @@ static void reg_regdb_query(const char *alpha2)
> >> >>
> >> >>       schedule_work(&reg_regdb_work);
> >> >>  }
> >> >> +
> >> >> +/* Feel free to add any other sanity checks here */
> >> >> +static void reg_regdb_size_check(void)
> >> >> +{
> >> >> +#ifdef CONFIG_CFG80211_REG_DEBUG
> >> >> +     BUILD_BUG_ON(!reg_regdb_size);
> >> >> +#else
> >> >> +     WARN_ONCE(!reg_regdb_size, "db.txt is empty, you should update it...");
> >> >> +#endif
> >> >
> >> > That ifdef seems a bit pointless? If anything I would have expected it
> >> > the other way around since the BUILD_BUG_ON compiles to nothing?
> >>
> >> As I tested it, the BUILD_BUG_ON() forces a compile failure.
> >
> > Right. Why would you not want that always?
> 
> Ah well that is a question for you, John and Stephen. I didn't use
> that *always* given that it would break random build testing whenever
> CFG80211_INTERNAL_REGDB was enabled, given that it requires a manual
> cp of db.txt from wireless-regdb. With this it would only break build
> testing with debugging cfg80211 regulatory, both
> CFG80211_INTERNAL_REGDB and CONFIG_CFG80211_REG_DEBUG enabled. If you
> guys are happy with it then so am I -- I prefer it, just didn't want
> any surprises or anyone reporting an unexpected build breakage later.

My first inclination is like Johannes, just break the build in this
case.  But the random build test breakage could be an annoyance for
the folks doing that.  I don't suppose there is any Kconfig magic
that would prevent selecting CFG80211_INTERNAL_REGDB unless there is
a non-zero db.txt file?

Also, I guess that an empty db.txt just forces the user back to
the build it "world" domain.  While that is less than ideal, it is
sufficient for some minimal functionality.  So breaking the build in
that case seems like bad form too.

Maybe a runtime warning is sufficient?

John
-- 
John W. Linville		Someday the world will need a hero, and you
linville@tuxdriver.com			might be all we have.  Be ready.