From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S1751282AbdAQTTM (ORCPT <rfc822;w@1wt.eu>);
        Tue, 17 Jan 2017 14:19:12 -0500
Received: from Galois.linutronix.de ([146.0.238.70]:46166 "EHLO
        Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S1750992AbdAQTSI (ORCPT
        <rfc822;linux-kernel@vger.kernel.org>);
        Tue, 17 Jan 2017 14:18:08 -0500
Date: Tue, 17 Jan 2017 20:17:43 +0100 (CET)
From: Thomas Gleixner <tglx@linutronix.de>
To: Vitaly Kuznetsov <vkuznets@redhat.com>
cc: Stephen Hemminger <stephen@networkplumber.org>,
        devel@linuxdriverproject.org, linux-kernel@vger.kernel.org,
        Haiyang Zhang <haiyangz@microsoft.com>,
        "K. Y. Srinivasan" <kys@microsoft.com>,
        John Stultz <john.stultz@linaro.org>, Alex Ng <alexng@microsoft.com>,
        Olaf Hering <olaf@aepfle.de>,
        Richard Cochran <richardcochran@gmail.com>
Subject: Re: [PATCH v3 2/2] hv_utils: implement Hyper-V PTP source
In-Reply-To: <87o9z5zk5h.fsf@vitty.brq.redhat.com>
Message-ID: <alpine.DEB.2.20.1701172016190.3645@nanos>
References: <20170117152719.23618-1-vkuznets@redhat.com> <20170117152719.23618-3-vkuznets@redhat.com> <20170117083547.3c7d71a4@xeon-e3> <87o9z5zk5h.fsf@vitty.brq.redhat.com>
User-Agent: Alpine 2.20 (DEB 67 2015-01-07)
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Tue, 17 Jan 2017, Vitaly Kuznetsov wrote:
> Stephen Hemminger <stephen@networkplumber.org> writes:
> >>  static int hv_timesync_init(struct hv_util_service *srv)
> >>  {
> >>  	INIT_WORK(&wrk.work, hv_set_host_time);
> >> +
> >> +	hv_ptp_clock = ptp_clock_register(&ptp_hyperv_info, NULL);
> >> +	if (IS_ERR_OR_NULL(hv_ptp_clock)) {
> >> +		pr_err("cannot register PTP clock: %ld\n",
> >> +		       PTR_ERR(hv_ptp_clock));
> >
> > Why not return error to init routine in case of failure.
> >
> >> +		hv_ptp_clock = NULL;
> >
> > Why not return error to init routine?  Rather than having user
> > scan log.
> >
> 
> The idea here was to not depend on CONFIG_PTP_1588_CLOCK. In case
> CONFIG_PTP_1588_CLOCK is disabled ptp_clock_register() will return NULL
> but the Hyper-V timesync driver remains functional - it still handles
> the ICTIMESYNCFLAG_SYNC case, just the ptp device will be missing.
> We can:
> 1) Put PTP-related code under #ifdef CONFIG_PTP_1588_CLOCK
> 2) Handle errors and NULL returned from ptp_clock_register() differently,
>    fail init in case we get an error and continue in case we see NULL.
> 3) Leave things as they are.
> 4) Always require CONFIG_PTP_1588_CLOCK.
> 
> My personal preference would be 2 or 3. What do you think?

Keep the current implementation and add a comment explaining the logic of
keeping the driver functional for the the ICTIMESYNC case.

Thanks,

	tglx