From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755491AbcGZJeO (ORCPT ); Tue, 26 Jul 2016 05:34:14 -0400 Received: from down.free-electrons.com ([37.187.137.238]:56735 "EHLO mail.free-electrons.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751213AbcGZJeL (ORCPT ); Tue, 26 Jul 2016 05:34:11 -0400 Subject: Re: [PATCH v3 1/4] hwmon: iio_hwmon: delay probing with late_initcall To: Alexander Stein References: <1469519027-11387-1-git-send-email-quentin.schulz@free-electrons.com> <209942367.uny0GxrY2s@ws-stein> <10d14cc4-26f1-8f2d-2997-3b2bc323c40e@free-electrons.com> <5277864.qlyRKbC1Zy@ws-stein> Cc: linux-kernel@vger.kernel.org, jdelvare@suse.com, linux@roeck-us.net, jic23@kernel.org, knaack.h@gmx.de, lars@metafoo.de, pmeerw@pmeerw.net, maxime.ripard@free-electrons.com, wens@csie.org, lee.jones@linaro.org, linux-hwmon@vger.kernel.org, linux-iio@vger.kernel.org, linux-arm-kernel@lists.infradead.org, thomas.petazzoni@free-electrons.com, antoine.tenart@free-electrons.com From: Quentin Schulz Message-ID: Date: Tue, 26 Jul 2016 11:33:59 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.2.0 MIME-Version: 1.0 In-Reply-To: <5277864.qlyRKbC1Zy@ws-stein> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 26/07/2016 11:05, Alexander Stein wrote: > On Tuesday 26 July 2016 10:24:48, Quentin Schulz wrote: >> On 26/07/2016 10:21, Alexander Stein wrote: >>> On Tuesday 26 July 2016 09:43:44, Quentin Schulz wrote: >>>> iio_channel_get_all returns -ENODEV when it cannot find either phandles >>>> and >>>> properties in the Device Tree or channels whose consumer_dev_name matches >>>> iio_hwmon in iio_map_list. The iio_map_list is filled in by iio drivers >>>> which might be probed after iio_hwmon. >>> >>> Would it work if iio_channel_get_all returning ENODEV is used for >>> returning >>> EPROBE_DEFER in iio_channel_get_all? Using late initcalls for >>> driver/device >>> dependencies seems not right for me at this place. >> >> Then what if the iio_channel_get_all is called outside of the probe of a >> driver? We'll have to change the error code, things we are apparently >> trying to avoid (see v2 patches' discussions). > > Maybe I didn't express my idea enough. I don't want to change the behavior of > iio_channel_get_all at all. Just the result evaluation of iio_channel_get_all > in iio_hwmon_probe. I have something link the patch below in mind. > > Best regards, > Alexander > --- > diff --git a/drivers/hwmon/iio_hwmon.c b/drivers/hwmon/iio_hwmon.c > index b550ba5..e32d150 100644 > --- a/drivers/hwmon/iio_hwmon.c > +++ b/drivers/hwmon/iio_hwmon.c > @@ -73,8 +73,12 @@ static int iio_hwmon_probe(struct platform_device *pdev) > name = dev->of_node->name; > > channels = iio_channel_get_all(dev); > - if (IS_ERR(channels)) > - return PTR_ERR(channels); > + if (IS_ERR(channels)) { > + if (PTR_ERR(channels) == -ENODEV) > + return -EPROBE_DEFER; > + else > + return PTR_ERR(channels); > + } > > st = devm_kzalloc(dev, sizeof(*st), GFP_KERNEL); > if (st == NULL) { Indeed, I misunderstood what you told me. Actually, the patch you proposed is part of my v1 (https://lkml.org/lkml/2016/6/28/203) and v2 (https://lkml.org/lkml/2016/7/15/215). Jonathan and Guenter didn't really like the idea of changing the -ENODEV in -EPROBE_DEFER. What I thought you were proposing was to change the -ENODEV return code inside iio_channel_get_all. This cannot be an option since the function might be called outside of a probe (it is not yet, but might be in the future?). Of what I understood, two possibilities are then possible (proposed either by Guenter or Jonathan): either rework the iio framework to register iio map array earlier or to use late_initcall instead of init for the driver consuming the iio channels. Thanks, Quentin