Hi, On 22/05/17 18:24, Johannes Berg wrote: > >> Couldn't userspace just look at NL80211_BSS_SEEN_MS_AGO to filter and >> create its own list? Given that the kernel provides the information >> userspace needs to figure out the age of a particular BSS, it doesn't >> seem like there needs to be a kernel tunable for this. Userspace can >> already avoid stale results. > > Yeah, I agree. It can also ask for a flush, so that old results are > gone by the time the next scan returns. We don't have a flush operation > without requesting a new scan, but I guess that could be added. > Ok, guess I understand what you're saying. Thanks for pointing me in the right direction. >> Also, different runtime situations might want different result ages, >> which wouldn't be possible if the kernel had a hardcoded maximum. >> Furthermore, different userspace apps might be reading the same scan >> list, and they might have different ideas about staleness. >> >> Or perhaps I misunderstand the problem, which could well be the case. > > No, I think this is perfectly right - userspace should be able to deal > with this given the tools we gave it, or if not, we should probably > just give it more tools instead of hardcoding the kernel configuration. > > This value really just kinda needed to be an upper bound so that we > don't start expiring entries while we're still scanning. > > johannes >
