linux-kernel - Re: [PATCH 2/2] regulator: assert that dummy regulator has been probed before using it

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Message-ID: <4945392.OV4Wx5bFTl@zbook-studio-g3>
Date: Mon, 10 Mar 2025 19:22:24 +0100
From: Christian Eggers <ceggers@....de>
To: Christian Eggers <ceggers@...i.de>, Mark Brown <broonie@...nel.org>
Cc: Liam Girdwood <lgirdwood@...il.com>,
 Douglas Anderson <dianders@...omium.org>, linux-kernel@...r.kernel.org,
 stable@...r.kernel.org
Subject:
 Re: [PATCH 2/2] regulator: assert that dummy regulator has been probed before
 using it

Am Montag, 10. März 2025, 18:23:02 CET schrieb Mark Brown:
> On Mon, Mar 10, 2025 at 05:33:02PM +0100, Christian Eggers wrote:
> > Due to asynchronous driver probing there is a chance that the dummy
> > regulator hasn't already been probed when first accessing it.
> > 
> >  		if (have_full_constraints()) {
> >  		
> >  			r = dummy_regulator_rdev;
> > 
> > +			BUG_ON(!r);
> > 
> >  			get_device(&r->dev);
> >  		
> >  		} else {
> >  		
> >  			dev_err(dev, "Failed to resolve %s-supply for 
%s\n",
> > 
> > @@ -2086,6 +2087,7 @@ static int regulator_resolve_supply(struct
> > regulator_dev *rdev)> 
> >  			goto out;
> >  		
> >  		}
> >  		r = dummy_regulator_rdev;
> > 
> > +		BUG_ON(!r);
> 
> This doesn't actually help anything
My idea was to help identifying the problem (if it is reintroduced again 
later).

> I'd expect this to trigger probe deferral.
I can check for this tomorrow.  But is it worth to use deferred probing
for a shared "NOP" driver which doesn't access any hardware?  Or would this 
only introduce overhead for nothing?

regards,
Christian