From: linux@roeck-us.net (Guenter Roeck)
To: linux-arm-kernel@lists.infradead.org
Subject: [v2,1/4] hwmon: iio_hwmon: defer probe when no channel is found
Date: Sat, 16 Jul 2016 10:00:13 -0700 [thread overview]
Message-ID: <20160716170013.GA27490@roeck-us.net> (raw)
In-Reply-To: <1468576754-3273-2-git-send-email-quentin.schulz@free-electrons.com>
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 <quentin.schulz@free-electrons.com>
> ---
>
> 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) {
next prev parent reply other threads:[~2016-07-16 17:00 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-07-15 9:59 [PATCH v2 0/4] add support for Allwinner SoCs ADC Quentin Schulz
2016-07-15 9:59 ` [PATCH v2 1/4] hwmon: iio_hwmon: defer probe when no channel is found Quentin Schulz
2016-07-16 17:00 ` Guenter Roeck [this message]
2016-07-18 10:02 ` [v2,1/4] " Maxime Ripard
2016-07-18 13:29 ` Guenter Roeck
2016-07-15 9:59 ` [PATCH v2 2/4] iio: adc: add support for Allwinner SoCs ADC Quentin Schulz
2016-07-18 12:57 ` Maxime Ripard
2016-07-19 9:04 ` Quentin Schulz
2016-07-19 12:40 ` Maxime Ripard
2016-07-18 13:18 ` Jonathan Cameron
2016-07-19 8:33 ` Quentin Schulz
2016-07-20 14:57 ` Jonathan Cameron
2016-07-21 12:15 ` Quentin Schulz
2016-07-23 6:37 ` Jonathan Cameron
2016-07-20 12:37 ` Quentin Schulz
2016-07-20 14:15 ` Crt Mori
2016-07-20 14:59 ` Jonathan Cameron
2016-07-15 9:59 ` [PATCH v2 3/4] mfd: " Quentin Schulz
2016-07-18 13:02 ` Maxime Ripard
2016-07-19 12:04 ` Quentin Schulz
2016-07-18 13:25 ` Jonathan Cameron
2016-07-19 7:31 ` Lee Jones
2016-07-20 15:01 ` Jonathan Cameron
2016-07-21 12:12 ` Lee Jones
2016-07-21 20:08 ` Maxime Ripard
2016-07-22 13:55 ` Lee Jones
2016-07-23 6:42 ` Jonathan Cameron
2016-07-25 9:55 ` Maxime Ripard
2016-07-19 8:35 ` Quentin Schulz
2016-07-15 9:59 ` [PATCH v2 4/4] hwmon: iio: add label for channels read by iio_hwmon Quentin Schulz
2016-07-15 14:03 ` Guenter Roeck
2016-07-15 14:36 ` Quentin Schulz
2016-07-16 2:53 ` Guenter Roeck
2016-07-18 12:24 ` Jonathan Cameron
2016-07-19 6:55 ` Quentin Schulz
2016-07-20 14:49 ` Jonathan Cameron
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