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From: Johannes Berg <johannes@sipsolutions.net>
To: Marcel Holtmann <marcel@holtmann.org>
Cc: Felix Fietkau <nbd@nbd.name>, linux-wireless@vger.kernel.org
Subject: Re: [PATCH v2] cfg80211: add local BSS receive time to survey information
Date: Wed, 28 Aug 2019 21:59:01 +0200	[thread overview]
Message-ID: <a15716609a2c88e1591581539fd637f7385571e4.camel@sipsolutions.net> (raw)
In-Reply-To: <F29BC537-AED5-4BFA-915F-ED8E749124FC@holtmann.org>

Hi Marcel,

> > No, as usual, that would break ABI. PAD is a regular attribute, just
> > empty and ignored for aligning 64-bit values.
> 
> then I do not grok on how the nla_put_u64_64bit works, but that is
> fine.
> 
> I assumed these are similar to the NL80211_SURVEY_INFO_MAX which we
> also always move, but also not expected to be part of the API as a
> fixed value.

No no, the _MAX is just the token we use for knowing what we want as the
maximum when parsing etc.

The _PAD is actually a real attribute, basically nla_put_u64_64bit()
will do "nla_put_flag(_PAD)" if and only if "offset % 8 == 0", in order
to actually 64-bit align the 64-bit value in the following attribute.

(Note that offset % 8 can only be 0 or 4, due to the way netlink
attributes work.)

johannes


  reply	other threads:[~2019-08-28 19:59 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-28 10:20 [PATCH v2] cfg80211: add local BSS receive time to survey information Felix Fietkau
2019-08-28 17:25 ` Marcel Holtmann
2019-08-28 19:44   ` Johannes Berg
2019-08-28 19:52     ` Marcel Holtmann
2019-08-28 19:59       ` Johannes Berg [this message]
2019-08-28 20:24         ` Marcel Holtmann
2019-08-28 20:28           ` Johannes Berg

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