Received-SPF: pass (google.com: best guess record for domain of linux-bluetooth-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Thu, 9 Jan 2020 22:29:35 +0100
From:   "michal.lowas-rzechonek@silvair.com" 
        <michal.lowas-rzechonek@silvair.com>
To:     "Stotland, Inga" <inga.stotland@intel.com>
Cc:     "Gix, Brian" <brian.gix@intel.com>,
        "linux-bluetooth@vger.kernel.org" <linux-bluetooth@vger.kernel.org>
Subject: Re: [PATCH BlueZ] mesh: Correctly generate NetKey list
Message-ID: <20200109212935.6dn5ivmnupfd5f2d@kynes>
Mail-Followup-To: "Stotland, Inga" <inga.stotland@intel.com>,
        "Gix, Brian" <brian.gix@intel.com>,
        "linux-bluetooth@vger.kernel.org" <linux-bluetooth@vger.kernel.org>
References: <20200109175715.22925-1-inga.stotland@intel.com>
 <20200109210006.e3qv6uxnr2w3isc5@kynes>
 <31a576190ecbd1ba3f7e779d746baf35815fbed9.camel@intel.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Disposition: inline
Content-Transfer-Encoding: 8bit
In-Reply-To: <31a576190ecbd1ba3f7e779d746baf35815fbed9.camel@intel.com>
User-Agent: NeoMutt/20180716
Sender: linux-bluetooth-owner@vger.kernel.org
Precedence: bulk

On 01/09, Stotland, Inga wrote:
>> Please don't use bit shifts for division.
> Why?

Because it's a different operation, and is less readable.  It's a
formula, so use math operators for numbers and bit operators for bits.

For example, idx_pair <<= 12 is fine, because the *context* is
bit-packing. Noone sane would write this as idx_pair *= 4096. This
reasoning applies the other way as well: don't write foo >> 2 where you
mean foo / 4.

>> Also, I think it's clearer to write this as:
>>     req_size = num_keys * 3 - num_keys % 2
>
> No, this is not how I read the spec. We need to pack 2 key indices in 3 octets.
> For example, 4 keys are packed in 6 octets and 5 keys are packed in 8 octets.

Yes, you're right. Sorry.

-- 
Michał Lowas-Rzechonek <michal.lowas-rzechonek@silvair.com>
Silvair http://silvair.com
Jasnogórska 44, 31-358 Krakow, POLAND