From mboxrd@z Thu Jan  1 00:00:00 1970
From: Stephen Hemminger <stephen@networkplumber.org>
Subject: Re: [RFC 02/14] virtio: use eth_link_read/write (and bug
 fix)
Date: Mon, 17 Jul 2017 09:01:22 -0700
Message-ID: <20170717090122.18655a27@xeon-e3>
References: <20170714183027.16021-1-stephen@networkplumber.org>
 <20170714183027.16021-3-stephen@networkplumber.org>
 <d1aab73b-bd85-5d9b-f8d3-cd38adda6ae8@solarflare.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Cc: <dev@dpdk.org>, Stephen Hemminger <sthemmin@microsoft.com>, Thomas
 Monjalon <thomas@monjalon.net>
To: Andrew Rybchenko <arybchenko@solarflare.com>
Return-path: <dev-bounces@dpdk.org>
Received: from mail-pf0-f175.google.com (mail-pf0-f175.google.com
 [209.85.192.175]) by dpdk.org (Postfix) with ESMTP id 3B9AE47CD
 for <dev@dpdk.org>; Mon, 17 Jul 2017 18:01:25 +0200 (CEST)
Received: by mail-pf0-f175.google.com with SMTP id q85so78510154pfq.1
 for <dev@dpdk.org>; Mon, 17 Jul 2017 09:01:25 -0700 (PDT)
In-Reply-To: <d1aab73b-bd85-5d9b-f8d3-cd38adda6ae8@solarflare.com>
List-Id: DPDK patches and discussions <dev.dpdk.org>
List-Unsubscribe: <http://dpdk.org/ml/options/dev>,
 <mailto:dev-request@dpdk.org?subject=unsubscribe>
List-Archive: <http://dpdk.org/ml/archives/dev/>
List-Post: <mailto:dev@dpdk.org>
List-Help: <mailto:dev-request@dpdk.org?subject=help>
List-Subscribe: <http://dpdk.org/ml/listinfo/dev>,
 <mailto:dev-request@dpdk.org?subject=subscribe>
Errors-To: dev-bounces@dpdk.org
Sender: "dev" <dev-bounces@dpdk.org>

On Sun, 16 Jul 2017 15:33:26 +0300
Andrew Rybchenko <arybchenko@solarflare.com> wrote:

> > +	link.link_autoneg = ETH_LINK_SPEED_FIXED;  
> 
> As I understand link_autoneg is 1 bit field with boolean semantics. I.e. 0/false - no autoneg, 1/true - autoneg.
> It looks like it has wrong comment:
>          uint16_t link_autoneg : 1;  /**< ETH_LINK_SPEED_[AUTONEG/FIXED] */
> 
> since
> #define ETH_LINK_SPEED_AUTONEG  (0 <<  0)  /**< Autonegotiate (all speeds) */
> #define ETH_LINK_SPEED_FIXED    (1 <<  0)  /**< Disable autoneg (fixed speed) */
> 
> whereas
> #define ETH_LINK_FIXED          0 /**< No autonegotiation. */
> #define ETH_LINK_AUTONEG        1 /**< Autonegotiated. */
> 
> In general this attempt to introduce bug is the result of wrong comment which is caused by very similar
> defines with opposite values.

Orignal observation was because some drivers (vmxnet3) were setting autoneg = fixed
and others were not. Turns out it makes no difference 
since FIXED == 0, the old code and new code have same effect.