linux-kernel - Re: [PATCH 1/2] hwmon: core: add thermal sensors only if dev->of

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Date:   Wed, 29 May 2019 16:12:56 -0700
From:   Eduardo Valentin <eduval@...zon.com>
To:     Guenter Roeck <linux@...ck-us.net>
CC:     Eduardo Valentin <eduval@...zon.com>,
        Jean Delvare <jdelvare@...e.com>,
        <linux-hwmon@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] hwmon: core: add thermal sensors only if
 dev->of_node is present

On Tue, May 28, 2019 at 08:08:21AM -0700, Guenter Roeck wrote:
> Hi Eduardo,
> 
> On Fri, May 17, 2019 at 04:13:36PM -0700, Eduardo Valentin wrote:
> > Drivers may register to hwmon and request for also registering
> > with the thermal subsystem (HWMON_C_REGISTER_TZ). However,
> > some of these driver, e.g. marvell phy, may be probed from
> > Device Tree or being dynamically allocated, and in the later
> > case, it will not have a dev->of_node entry.
> > 
> > Registering with hwmon without the dev->of_node may result in
> > different outcomes depending on the device tree, which may
> > be a bit misleading. If the device tree blob has no 'thermal-zones'
> > node, the *hwmon_device_register*() family functions are going
> > to gracefully succeed, because of-thermal,
> > *thermal_zone_of_sensor_register() return -ENODEV in this case,
> > and the hwmon error path handles this error code as success to
> > cover for the case where CONFIG_THERMAL_OF is not set.
> > However, if the device tree blob has the 'thermal-zones'
> > entry, the *hwmon_device_register*() will always fail on callers
> > with no dev->of_node, propagating -EINVAL.
> > 
> > If dev->of_node is not present, calling of-thermal does not
> > make sense. For this reason, this patch checks first if the
> > device has a of_node before going over the process of registering
> > with the thermal subsystem of-thermal interface. And in this case,
> > when a caller of *hwmon_device_register*() with HWMON_C_REGISTER_TZ
> > and no dev->of_node will still register with hwmon, but not with
> > the thermal subsystem. If all the hwmon part bits are in place,
> > the registration will succeed.
> > 
> Makes sense. I'd apply it as-is, but it would be better if you resend
> it to the list to give others a chance to comment.

Ok Cool.

Yeah, the patches were copied to the mailing list. Only the cover letter
somehow I forgot to copy the mailing lists while git-sending-email.

I will resend the two patches (and the cover letter) after fixing
the comment on patch 2/2.

> 
> Thanks,
> Guenter
> 
> > Cc: Jean Delvare <jdelvare@...e.com>
> > Cc: Guenter Roeck <linux@...ck-us.net>
> > Cc: linux-hwmon@...r.kernel.org
> > Cc: linux-kernel@...r.kernel.org
> > Signed-off-by: Eduardo Valentin <eduval@...zon.com>
> > ---
> >  drivers/hwmon/hwmon.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/hwmon/hwmon.c b/drivers/hwmon/hwmon.c
> > index fcdbac4a56e3..6b3559f58b67 100644
> > --- a/drivers/hwmon/hwmon.c
> > +++ b/drivers/hwmon/hwmon.c
> > @@ -619,7 +619,7 @@ __hwmon_device_register(struct device *dev, const char *name, void *drvdata,
> >  	if (err)
> >  		goto free_hwmon;
> >  
> > -	if (dev && chip && chip->ops->read &&
> > +	if (dev && dev->of_node && chip && chip->ops->read &&
> >  	    chip->info[0]->type == hwmon_chip &&
> >  	    (chip->info[0]->config[0] & HWMON_C_REGISTER_TZ)) {
> >  		const struct hwmon_channel_info **info = chip->info;
> > -- 
> > 2.21.0
> > 

-- 
All the best,
Eduardo Valentin