linux-kernel - Re: [PATCH] backlight: pwm_bl: print errno for probe errors

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Message-ID: <27b41b77ec4071b29402592f2084b30c17ca1d6a.camel@ginzinger.com>
Date: Thu, 1 Aug 2024 10:12:37 +0000
From: Kepplinger-Novakovic Martin <Martin.Kepplinger-Novakovic@...zinger.com>
To: "u.kleine-koenig@...libre.com" <u.kleine-koenig@...libre.com>
CC: "daniel.thompson@...aro.org" <daniel.thompson@...aro.org>,
	"lee@...nel.org" <lee@...nel.org>, "linux-pwm@...r.kernel.org"
	<linux-pwm@...r.kernel.org>, "jingoohan1@...il.com" <jingoohan1@...il.com>,
	"linux-fbdev@...r.kernel.org" <linux-fbdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>
Subject: Re: [PATCH] backlight: pwm_bl: print errno for probe errors

Am Donnerstag, dem 01.08.2024 um 12:09 +0200 schrieb Uwe Kleine-König:
> Hello Martin,
> 
> On Thu, Aug 01, 2024 at 09:52:01AM +0000, Kepplinger-Novakovic Martin
> wrote:
> > Am Donnerstag, dem 01.08.2024 um 11:26 +0200 schrieb Uwe Kleine-
> > König:
> > > On Thu, Aug 01, 2024 at 11:12:55AM +0200, Martin Kepplinger-
> > > Novaković
> > > wrote:
> > > > diff --git a/drivers/video/backlight/pwm_bl.c
> > > > b/drivers/video/backlight/pwm_bl.c
> > > > index f1005bd0c41e3..cc7e7af71891f 100644
> > > > --- a/drivers/video/backlight/pwm_bl.c
> > > > +++ b/drivers/video/backlight/pwm_bl.c
> > > > @@ -502,7 +502,8 @@ static int pwm_backlight_probe(struct
> > > > platform_device *pdev)
> > > >                                                   GPIOD_ASIS);
> > > >         if (IS_ERR(pb->enable_gpio)) {
> > > >                 ret = dev_err_probe(&pdev->dev, PTR_ERR(pb-
> > > > > enable_gpio),
> > > > -                                   "failed to acquire enable
> > > > GPIO\n");
> > > > +                                   "failed to acquire enable
> > > > GPIO:
> > > > %ld\n",
> > > > +                                   PTR_ERR(pb->enable_gpio));
> > > 
> > > AFAIK dev_err_probe already emits the error code passed as 2nd
> > > parameter. So I wonder about this patch's benefit.
> > > 
> > 
> > It does. Other messages only take the deferred_probe_reason without
> > the
> > error code. It's actually fine if users properly enable debugging
> > after
> > seeing an error and then this change is not needed :)
> 
> I'm unsure what you intend to say here. Do you agree that this patch
> doesn't need to be applied as it doesn't add any information to the
> emitted messages? Or do you think there is a value because "users
> don't
> need to enable debugging" then. In the latter case I don't see where
> users would see "failed to acquire enable GPIO" before, but not the
> value of the error code.
> 

hi Uwe, sorry, I agree that this patch doesn't add any information. I
think it can be expected to look at debug when drivers don't probe.

thanks,
                         martin

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