On Tuesday 26 July 2016 11:33:59, Quentin Schulz wrote:

On 26/07/2016 11:05, Alexander Stein wrote:

quoted

On Tuesday 26 July 2016 10:24:48, Quentin Schulz wrote:

quoted

On 26/07/2016 10:21, Alexander Stein wrote:

quoted

On Tuesday 26 July 2016 09:43:44, Quentin Schulz wrote:

quoted

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.

Thanks for the links.

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?).

AFAICS this is a helper function not knowing about device probing itself. And 
it should stay at that.

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.

Interestingly using this problem would not arise due to module dependencies. 
But using late_initcall would mean this needs to be done on any driver using 
iio channels? I would rather keep those consumers simple.

Best regards,
Alexander