linux-kernel - Re: [PATCH] thermal: sun8i: Be loud when probe fails

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Date:   Mon, 20 Jul 2020 09:28:03 +0100
From:   Russell King - ARM Linux admin <linux@...linux.org.uk>
To:     Icenowy Zheng <icenowy@...c.io>
Cc:     Ondrej Jirman <megous@...ous.com>,
        Amit Kucheria <amit.kucheria@...durent.com>,
        "open list:ALLWINNER THERMAL DRIVER" <linux-pm@...r.kernel.org>,
        Yangtao Li <tiny.windzz@...il.com>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        open list <linux-kernel@...r.kernel.org>,
        Maxime Ripard <mripard@...nel.org>,
        Vasily Khoruzhick <anarsoul@...il.com>,
        linux-sunxi@...glegroups.com, Zhang Rui <rui.zhang@...el.com>,
        Chen-Yu Tsai <wens@...e.org>,
        "moderated list:ARM/Allwinner sunXi SoC support" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH] thermal: sun8i: Be loud when probe fails

On Mon, Jul 20, 2020 at 03:55:26PM +0800, Icenowy Zheng wrote:
> 在 2020-07-08星期三的 12:03 +0100，Russell King - ARM Linux admin写道：
> > On Wed, Jul 08, 2020 at 12:55:27PM +0200, Ondrej Jirman wrote:
> > > I noticed several mobile Linux distributions failing to enable the
> > > thermal regulation correctly, because the kernel is silent
> > > when thermal driver fails to probe. Add enough error reporting
> > > to debug issues and warn users in case thermal sensor is failing
> > > to probe.
> > > 
> > > Failing to notify users means, that SoC can easily overheat under
> > > load.
> > > 
> > > Signed-off-by: Ondrej Jirman <megous@...ous.com>
> > > ---
> > >  drivers/thermal/sun8i_thermal.c | 55 ++++++++++++++++++++++++++---
> > > ----
> > >  1 file changed, 43 insertions(+), 12 deletions(-)
> > > 
> > > diff --git a/drivers/thermal/sun8i_thermal.c
> > > b/drivers/thermal/sun8i_thermal.c
> > > index 74d73be16496..9065e79ae743 100644
> > > --- a/drivers/thermal/sun8i_thermal.c
> > > +++ b/drivers/thermal/sun8i_thermal.c
> > > @@ -287,8 +287,12 @@ static int sun8i_ths_calibrate(struct
> > > ths_device *tmdev)
> > >  
> > >  	calcell = devm_nvmem_cell_get(dev, "calibration");
> > >  	if (IS_ERR(calcell)) {
> > > +		dev_err(dev, "Failed to get calibration nvmem cell
> > > (%ld)\n",
> > > +			PTR_ERR(calcell));
> > 
> > Consider using:
> > 
> > 		dev_err(dev, "Failed to get calibration nvmem cell
> > (%pe)\n",
> > 			calcell);
> > 
> > which means the kernel can print the symbolic errno value.
> 
> Oh interesting format here.
> 
> When we need to deal with a int return value, is it "%e"?

No, because that will lose the ability for the compiler to check the
format string and arguments correspond.  All the extensions are
documented at Documentation/core-api/printk-formats.rst.

Use %pe and ERR_PTR(...) to print an integer -ve errno return value.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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