Received-SPF: pass (google.com: best guess record for domain of linux-wireless-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Content-Type: text/plain;
        charset=us-ascii
Mime-Version: 1.0 (Mac OS X Mail 12.4 \(3445.104.11\))
Subject: Re: [PATCH v2] cfg80211: add local BSS receive time to survey
 information
From:   Marcel Holtmann <marcel@holtmann.org>
In-Reply-To: <a15716609a2c88e1591581539fd637f7385571e4.camel@sipsolutions.net>
Date:   Wed, 28 Aug 2019 22:24:21 +0200
Cc:     Felix Fietkau <nbd@nbd.name>, linux-wireless@vger.kernel.org
Content-Transfer-Encoding: 8BIT
Message-Id: <F130F474-2D74-4952-B94B-82200B1D6CB6@holtmann.org>
References: <20190828102042.58016-1-nbd@nbd.name>
 <9189B2C1-6E5B-4457-9354-A010F946EE33@holtmann.org>
 <18c4232675c7b4f13fbfe9e5d8e9364a0908f316.camel@sipsolutions.net>
 <F29BC537-AED5-4BFA-915F-ED8E749124FC@holtmann.org>
 <a15716609a2c88e1591581539fd637f7385571e4.camel@sipsolutions.net>
To:     Johannes Berg <johannes@sipsolutions.net>
Sender: linux-wireless-owner@vger.kernel.org
Precedence: bulk

Hi Johannes,

>>> 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.)

I get that part now. So the kernel is inserting a _PAD, but userspace is still not doing that. So for NL80211_ATTR_WDEV we should be doing the same actually?

Regards

Marcel