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

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Message-ID: <3ghsuulqhfqvktfqbo7hfewpgu2nbyxahjxmoqfkvpceepmqih@axneh72aegog>
Date: Thu, 1 Aug 2024 12:09:12 +0200
From: Uwe Kleine-König <u.kleine-koenig@...libre.com>
To: 
	Kepplinger-Novakovic Martin <Martin.Kepplinger-Novakovic@...zinger.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

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.

Best regards
Uwe

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