linux-kernel - Re: [PATCH] regulator: Don't print error in devm_regulator_bulk_get() on -EPROBE

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Date:	Wed, 16 Mar 2016 11:37:15 +0000
From:	Mark Brown <broonie@...nel.org>
To:	Javier Martinez Canillas <javier@....samsung.com>
Cc:	linux-kernel@...r.kernel.org, Liam Girdwood <lgirdwood@...il.com>
Subject: Re: [PATCH] regulator: Don't print error in
 devm_regulator_bulk_get() on -EPROBE_DEFER

On Wed, Mar 16, 2016 at 08:19:42AM -0300, Javier Martinez Canillas wrote:
> On 03/16/2016 06:59 AM, Mark Brown wrote:
> > On Tue, Mar 15, 2016 at 05:35:14PM -0300, Javier Martinez Canillas wrote:

> > We've been through this repeatedly - this is the case for all probe
> > deferrals and if we just don't print the errors at all then people won't
> > be able to tell if they've got a missing dependency.  We need people to

> I wonder if we can use a dev_dbg() then so it will be printed at debug level.
> That way users can have that info if they want but not pollute the boot log.

No, that has exactly the same problems.

> Basically I want to get rid of things like this:

> [    1.438422] exynos-hdmi 14530000.hdmi: Failed to get supply 'vdd': -517
> [    1.443638] [drm:hdmi_probe] *ERROR* failed to get regulators
> [    1.449326] [drm:hdmi_probe] *ERROR* hdmi_resources_init failed

> The HDMI driver probed correctly but looking at the log it seems that things
> failed so can mislead users not familiar with the probe deferral mechanism.

So fix probe deferral.  Don't go through the entire kernel hacking in
bodges everywhere, if we have to hack the error handling for almost all
resource acquisition errors during probe that's obviously not sensible.

> > work on things like allowing the kernel to make use of the dependency
> > information it has to order probes more sensibly.

> Agreed, I've seen Tomeu's patches and the following discussions.

Raphael was proposing something a bit different there.

> > Raphael had some ideas he was talking about at Kernel Summit for this,
> > Russell King also proposed just suppressing the errors until we're at
> > the last deferred probe run at the end of init.

> Suppressing errors is a nice idea but will again lead to false positives
> when the drivers are built as a module AFAICT.

It's not a fix, it's just a 90% masking of the problem that does
everything in one place rather than being lots of individual changes.
Modules are always going to be problematic for this and in any case the
thing there is that we need similar enhancements in the userspace
utilities.

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