linux-kernel - Re: [PATCH RFT 3/5] hwmon: Add support for updating thermal zones

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Message-ID: <ae5f1ab3-cd0e-4831-9a11-30dc75f16da0@roeck-us.net>
Date: Fri, 30 Jan 2026 07:44:24 -0800
From: Guenter Roeck <linux@...ck-us.net>
To: linux-hwmon@...r.kernel.org
Cc: linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
 Jaroslav Pulchart <jaroslav.pulchart@...ddata.com>,
 "Rafael J . Wysocki" <rafael@...nel.org>, lihuisong <lihuisong@...wei.com>
Subject: Re: [PATCH RFT 3/5] hwmon: Add support for updating thermal zones

On 1/23/26 10:22, Guenter Roeck wrote:
> Implement support for updating thermal zones. This is necessary
> to be able to handle updates to sysfs attribute visibility.
> 
> Signed-off-by: Guenter Roeck <linux@...ck-us.net>

This patch is both racy because it doesn't protect the list of thermal
zones, and it leaks tzdata until the device is removed. SO it will need
(much) more work.

Guenter

> ---
>   drivers/hwmon/hwmon.c | 34 +++++++++++++++++++++++++++-------
>   1 file changed, 27 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/hwmon/hwmon.c b/drivers/hwmon/hwmon.c
> index 1f35285ca7a0..cb89218a0b6a 100644
> --- a/drivers/hwmon/hwmon.c
> +++ b/drivers/hwmon/hwmon.c
> @@ -276,7 +276,7 @@ static struct hwmon_thermal_data *hwmon_thermal_find_tz(struct device *dev, int
>   	return NULL;
>   }
>   
> -static int hwmon_thermal_register_sensors(struct device *dev)
> +static int hwmon_thermal_handle_sensors(struct device *dev, bool update)
>   {
>   	struct hwmon_device *hwdev = to_hwmon_device(dev);
>   	const struct hwmon_chip_info *chip = hwdev->chip;
> @@ -294,22 +294,42 @@ static int hwmon_thermal_register_sensors(struct device *dev)
>   			continue;
>   
>   		for (j = 0; info[i]->config[j]; j++) {
> +			umode_t mode;
>   			int err;
>   
> -			if (!(info[i]->config[j] & HWMON_T_INPUT) ||
> -			    !hwmon_is_visible(chip->ops, drvdata, hwmon_temp,
> -					      hwmon_temp_input, j))
> +			if (!(info[i]->config[j] & HWMON_T_INPUT))
>   				continue;
> +			mode = hwmon_is_visible(chip->ops, drvdata, hwmon_temp,
> +						hwmon_temp_input, j);
> +			if (!mode) {
> +				struct hwmon_thermal_data *tzdata;
>   
> -			err = hwmon_thermal_add_sensor(dev, j);
> -			if (err)
> -				return err;
> +				if (!update)
> +					continue;
> +				tzdata = hwmon_thermal_find_tz(dev, j);
> +				if (tzdata) {
> +					devm_thermal_of_zone_unregister(dev, tzdata->tzd);
> +					devm_release_action(dev, hwmon_thermal_remove_sensor,
> +							    &tzdata->node);
> +				}
> +			} else {
> +				if (!update || !hwmon_thermal_find_tz(dev, j)) {
> +					err = hwmon_thermal_add_sensor(dev, j);
> +					if (err)
> +						return err;
> +				}
> +			}
>   		}
>   	}
>   
>   	return 0;
>   }
>   
> +static int hwmon_thermal_register_sensors(struct device *dev)
> +{
> +	return hwmon_thermal_handle_sensors(dev, false);
> +}
> +
>   static void hwmon_thermal_notify(struct device *dev, int index)
>   {
>   	struct hwmon_thermal_data *tzdata = hwmon_thermal_find_tz(dev, index);