linux-kernel - Re: Regulator probe on demand (or circular dependencies)

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Message-ID: <20191209171323.GI5483@sirena.org.uk>
Date:   Mon, 9 Dec 2019 17:13:23 +0000
From:   Mark Brown <broonie@...nel.org>
To:     Kieran Bingham <kieran.bingham@...asonboard.com>
Cc:     Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Jacopo Mondi <jacopo@...ndi.org>,
        Niklas Söderlund 
        <niklas.soderlund@...natech.se>
Subject: Re: Regulator probe on demand (or circular dependencies)

On Mon, Dec 09, 2019 at 05:03:38PM +0000, Kieran Bingham wrote:
> On 09/12/2019 16:37, Mark Brown wrote:
> > On Fri, Dec 06, 2019 at 04:38:04PM +0000, Kieran Bingham wrote:

> >> The MAX9286 also exposes 2 GPIO pins, as such I have configured the
> >> MAX9286 driver [1] to expose a gpio-chip [2].

> > So this seems like a MFD then?  The nice thing about using the MFD
> > subsystem is that it means that the drivers for the various subsystems
> > on the device can instantiate in any order and defer separately without
> > interfering with each other which seems like it's the issue here.

> Well that's part of the problem... the V4L2 async framework can not
> currently support the device performing a probe-defer at all, so it
> *will* fail later (and crash currently).

> I hope we can fix this sometime - but it's a recurring pain point it
> seems. Unless it's just our video-capture driver, I'll have to dig
> deeper here, and check with Niklas.

Yes, that seems like something that should be fixed anyway - if nothing
else for the most part probe defer error handling is just error
handling.

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