linux-kernel - Re: [PATCH] mtd: intel-dg: wake card on operations

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Message-ID: <aPebJrWsqMCKmMpX@smile.fi.intel.com>
Date: Tue, 21 Oct 2025 17:39:34 +0300
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To: "Usyskin, Alexander" <alexander.usyskin@...el.com>
Cc: Miquel Raynal <miquel.raynal@...tlin.com>,
	Richard Weinberger <richard@....at>,
	Vignesh Raghavendra <vigneshr@...com>,
	"linux-mtd@...ts.infradead.org" <linux-mtd@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Abliyev, Reuven" <reuven.abliyev@...el.com>,
	"De Marchi, Lucas" <lucas.demarchi@...el.com>
Subject: Re: [PATCH] mtd: intel-dg: wake card on operations

On Tue, Oct 21, 2025 at 12:51:30PM +0000, Usyskin, Alexander wrote:
> > On Mon, Oct 20, 2025 at 01:09:10PM +0300, Andy Shevchenko wrote:
> > > On Sun, Oct 19, 2025 at 06:01:45PM +0300, Alexander Usyskin wrote:

...

> > > > +	devm_pm_runtime_enable(device);
> > >
> > > Please, justify why this code is good without error checking. Before doing
> > that
> > > think for a moment for the cases when devm_*() might be developed in the
> > future
> > > and return something interesting (if not yet).
> 
> We should not fail the probe because of runtime  pm enablement failure, I suppose.
> There are other ways to keep card awake.
> The pm_runtime_* functions work without runtime_enable but have no effect.
> Thus, we can ignore failure here.

Using devm_*() in such a case is misleading. It incorporates errors from
different layers and ignoring both is odd.

I would suggest to avoid using devm_*() in this case and put a comment on
the ignored PM errors (however, personally I think this approach is wrong).

...

> > > >  err:
> > > > +	pm_runtime_put(device);
> > > > +err_norpm:
> > > >  	kref_put(&nvm->refcnt, intel_dg_nvm_release);
> > > >  	return ret;
> > >
> > > Mixing devm with non-devm usually lead to hard to catch bugs in the error
> > paths
> > > / remove stages with ordering of cleaning resources up.
> 
> I see that this pattern is reasonably common in drivers.
> There can't be devm wrappers for pm_runtime_get/put and these functions works
> regardless of enable status.

It can be wrapped to become a managed resource, but the problem is that you are
ignoring errors from it, which I consider a bit incorrect.

-- 
With Best Regards,
Andy Shevchenko