linux-kernel - Re: [PATCH 1/3] hwmon: (dell-smm) Fail probing when cooling device registration fails

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Date:   Mon, 22 Aug 2022 09:17:12 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Armin Wolf <W_Armin@....de>
Cc:     Pali Rohár <pali@...nel.org>, jdelvare@...e.com,
        linux-hwmon@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] hwmon: (dell-smm) Fail probing when cooling device
 registration fails

On Sun, Aug 21, 2022 at 09:11:24PM +0200, Armin Wolf wrote:
> Am 21.08.22 um 17:41 schrieb Pali Rohár:
> 
> > On Sunday 21 August 2022 17:17:11 Armin Wolf wrote:
> > > Previously, it was thought that failing to register a cooling device
> > > would not be critical, so the probing was not aborted in such a case.
> > > This however would lead to userspace being unable to rely on those
> > > cooling devices, since they might not represent all fans being present.
> > > Fix that by failing probing when cooling device registration fails.
> > This patch does not fix address this issue fully. CONFIG_THERMAL can be
> > disabled during compile time and then cooling device would not be
> > registered too.
> 
> I though of the cooling device feature as being optional "as a whole".
> So when CONFIG_THERMAL is disabled during compile time, the driver does
> not create any cooling devices. If however CONFIG_THERMAL was enabled
> during compile time, the driver should fail probing if it cannot register
> all cooling devices.
> 

I disagree. The primary objective of this driver is to report environmental
data. Support for the thermal subsystem is an add-on. If instantiating
the thermal device fails, the driver should at least report temperatures
and fan speeds, as it did before thermal support was added.

Thanks,
Guenter

> Armin Wolf
> 
> > > Tested on a Dell Inspiron 3505.
> > > 
> > > Fixes: e0d3f7cb2606 ("hwmon: (dell-smm) Add cooling device support")
> > > Signed-off-by: Armin Wolf <W_Armin@....de>
> > > ---
> > >   drivers/hwmon/dell-smm-hwmon.c | 4 +---
> > >   1 file changed, 1 insertion(+), 3 deletions(-)
> > > 
> > > diff --git a/drivers/hwmon/dell-smm-hwmon.c b/drivers/hwmon/dell-smm-hwmon.c
> > > index 7f8d95dd2717..1dab7591576a 100644
> > > --- a/drivers/hwmon/dell-smm-hwmon.c
> > > +++ b/drivers/hwmon/dell-smm-hwmon.c
> > > @@ -1013,12 +1013,10 @@ static int __init dell_smm_init_hwmon(struct device *dev)
> > > 
> > >   		data->fan[i] = true;
> > > 
> > > -		/* the cooling device is not critical, ignore failures */
> > >   		if (IS_REACHABLE(CONFIG_THERMAL)) {
> > >   			err = dell_smm_init_cdev(dev, i);
> > >   			if (err < 0)
> > > -				dev_warn(dev, "Failed to register cooling device for fan %u\n",
> > > -					 i + 1);
> > > +				return err;
> > >   		}
> > > 
> > >   		data->fan_nominal_speed[i] = devm_kmalloc_array(dev, data->i8k_fan_max + 1,
> > > --
> > > 2.30.2
> > >