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    SubjectRe: [PATCH v3 1/4] hwmon: iio_hwmon: delay probing with late_initcall
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    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

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