From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from bh-25.webhostbox.net ([208.91.199.152]:36555 "EHLO bh-25.webhostbox.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751540AbcGPRAX (ORCPT ); Sat, 16 Jul 2016 13:00:23 -0400 Date: Sat, 16 Jul 2016 10:00:13 -0700 From: Guenter Roeck To: Quentin Schulz Cc: jdelvare@suse.com, 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-kernel@vger.kernel.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 Subject: Re: [v2,1/4] hwmon: iio_hwmon: defer probe when no channel is found Message-ID: <20160716170013.GA27490@roeck-us.net> References: <1468576754-3273-2-git-send-email-quentin.schulz@free-electrons.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1468576754-3273-2-git-send-email-quentin.schulz@free-electrons.com> Sender: linux-hwmon-owner@vger.kernel.org List-Id: linux-hwmon@vger.kernel.org On Fri, Jul 15, 2016 at 11:59:11AM +0200, 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. > > It is better to defer the probe of iio_hwmon if such error is returned by > iio_channel_get_all in order to let a chance to iio drivers to expose > channels in iio_map_list. > > Signed-off-by: Quentin Schulz > --- > > No modifications for this patch since we did not settled for a solution. > What should we do? > AFAICS the only thing we can do is to replace module_platform_driver() with its explicitly coded variant, and to use use late_initcall() instead of module_init(). Anything else would result in endless probe deferrals if there are no channels. Guenter > drivers/hwmon/iio_hwmon.c | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) > > diff --git a/drivers/hwmon/iio_hwmon.c b/drivers/hwmon/iio_hwmon.c > index b550ba5..c0da4d9 100644 > --- a/drivers/hwmon/iio_hwmon.c > +++ b/drivers/hwmon/iio_hwmon.c > @@ -73,8 +73,11 @@ static int iio_hwmon_probe(struct platform_device *pdev) > name = dev->of_node->name; > > channels = iio_channel_get_all(dev); > - if (IS_ERR(channels)) > + if (IS_ERR(channels)) { > + if (PTR_ERR(channels) == -ENODEV) > + return -EPROBE_DEFER; > return PTR_ERR(channels); > + } > > st = devm_kzalloc(dev, sizeof(*st), GFP_KERNEL); > if (st == NULL) { From mboxrd@z Thu Jan 1 00:00:00 1970 From: linux@roeck-us.net (Guenter Roeck) Date: Sat, 16 Jul 2016 10:00:13 -0700 Subject: [v2,1/4] hwmon: iio_hwmon: defer probe when no channel is found In-Reply-To: <1468576754-3273-2-git-send-email-quentin.schulz@free-electrons.com> References: <1468576754-3273-2-git-send-email-quentin.schulz@free-electrons.com> Message-ID: <20160716170013.GA27490@roeck-us.net> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Fri, Jul 15, 2016 at 11:59:11AM +0200, 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. > > It is better to defer the probe of iio_hwmon if such error is returned by > iio_channel_get_all in order to let a chance to iio drivers to expose > channels in iio_map_list. > > Signed-off-by: Quentin Schulz > --- > > No modifications for this patch since we did not settled for a solution. > What should we do? > AFAICS the only thing we can do is to replace module_platform_driver() with its explicitly coded variant, and to use use late_initcall() instead of module_init(). Anything else would result in endless probe deferrals if there are no channels. Guenter > drivers/hwmon/iio_hwmon.c | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) > > diff --git a/drivers/hwmon/iio_hwmon.c b/drivers/hwmon/iio_hwmon.c > index b550ba5..c0da4d9 100644 > --- a/drivers/hwmon/iio_hwmon.c > +++ b/drivers/hwmon/iio_hwmon.c > @@ -73,8 +73,11 @@ static int iio_hwmon_probe(struct platform_device *pdev) > name = dev->of_node->name; > > channels = iio_channel_get_all(dev); > - if (IS_ERR(channels)) > + if (IS_ERR(channels)) { > + if (PTR_ERR(channels) == -ENODEV) > + return -EPROBE_DEFER; > return PTR_ERR(channels); > + } > > st = devm_kzalloc(dev, sizeof(*st), GFP_KERNEL); > if (st == NULL) {