linux-kernel - Re: [PATCH] regulator: pwm: Don't warn on probe deferral

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Date:   Wed, 26 Feb 2020 17:17:57 +0100
From:   Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>
To:     Mark Brown <broonie@...nel.org>
Cc:     Jon Hunter <jonathanh@...dia.com>,
        Liam Girdwood <lgirdwood@...il.com>,
        Thierry Reding <thierry.reding@...il.com>,
        linux-kernel@...r.kernel.org, linux-pwm@...r.kernel.org,
        linux-tegra@...r.kernel.org
Subject: Re: [PATCH] regulator: pwm: Don't warn on probe deferral

On Mon, Feb 24, 2020 at 04:58:59PM +0000, Mark Brown wrote:
> On Mon, Feb 24, 2020 at 02:40:48PM +0000, Jon Hunter wrote:
> > Deferred probe is an expected return value for devm_pwm_get(). Given
> > that the driver deals with it properly, there's no need to output a
> > warning that may potentially confuse users.
> 
> >  		ret = PTR_ERR(drvdata->pwm);
> > -		dev_err(&pdev->dev, "Failed to get PWM: %d\n", ret);
> > +		if (ret != -EPROBE_DEFER)
> > +			dev_err(&pdev->dev, "Failed to get PWM: %d\n", ret);
> 
> This then means that there's no way for users to determine why the
> driver has failed to instantiate which can be frustrating.  It'd be
> better to at least have some dev_dbg() output when deferring so that
> there's something for people to go on without having to instrument the
> code.

Not printing an error message is quite usual however. I think a generic
approach that for example makes the list of devices that should be
retried to probe on the next opportunity inspectable would be nice.

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |