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

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Message-ID: <20190528150821.GB5516@roeck-us.net>
Date:   Tue, 28 May 2019 08:08:21 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Eduardo Valentin <eduval@...zon.com>
Cc:     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

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.

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
>