linux-kernel - Re: [PATCH v2 2/2] hwmon: Add "label" attribute

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Date:   Sun, 9 Jan 2022 17:29:24 -0800
From:   Guenter Roeck <linux@...ck-us.net>
To:     Paul Cercueil <paul@...pouillou.net>
Cc:     Jean Delvare <jdelvare@...e.com>, Jonathan Corbet <corbet@....net>,
        linux-hwmon@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-doc@...r.kernel.org, list@...ndingux.net,
        Cosmin Tanislav <cosmin.tanislav@...log.com>
Subject: Re: [PATCH v2 2/2] hwmon: Add "label" attribute

On Wed, Jan 05, 2022 at 03:15:51PM +0000, Paul Cercueil wrote:
> If a label is defined in the device tree for this device add that
> to the device specific attributes. This is useful for userspace to
> be able to identify an individual device when multiple identical
> chips are present in the system.
> 
> Signed-off-by: Paul Cercueil <paul@...pouillou.net>
> Tested-by: Cosmin Tanislav <cosmin.tanislav@...log.com>
> Reported-by: kernel test robot <lkp@...el.com>
> ---
> 
> Notes:
>     v2: - Cache label into hwmon_device
>         - Rename hwmon_dev_name_is_visible() to hwmon_dev_attr_is_visible()
> 	- Add missing <linux/property.h> include
> 
>  drivers/hwmon/hwmon.c | 34 +++++++++++++++++++++++++++++++---
>  1 file changed, 31 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/hwmon/hwmon.c b/drivers/hwmon/hwmon.c
> index 3501a3ead4ba..22e1b47c09fc 100644
> --- a/drivers/hwmon/hwmon.c
> +++ b/drivers/hwmon/hwmon.c
> @@ -18,6 +18,7 @@
>  #include <linux/list.h>
>  #include <linux/module.h>
>  #include <linux/pci.h>
> +#include <linux/property.h>
>  #include <linux/slab.h>
>  #include <linux/string.h>
>  #include <linux/thermal.h>
> @@ -30,6 +31,7 @@
>  
>  struct hwmon_device {
>  	const char *name;
> +	const char *label;
>  	struct device dev;
>  	const struct hwmon_chip_info *chip;
>  	struct list_head tzdata;
> @@ -71,17 +73,29 @@ name_show(struct device *dev, struct device_attribute *attr, char *buf)
>  }
>  static DEVICE_ATTR_RO(name);
>  
> +static ssize_t
> +label_show(struct device *dev, struct device_attribute *attr, char *buf)
> +{
> +	return sysfs_emit(buf, "%s\n", to_hwmon_device(dev)->label);
> +}
> +static DEVICE_ATTR_RO(label);
> +
>  static struct attribute *hwmon_dev_attrs[] = {
>  	&dev_attr_name.attr,
> +	&dev_attr_label.attr,
>  	NULL
>  };
>  
> -static umode_t hwmon_dev_name_is_visible(struct kobject *kobj,
> +static umode_t hwmon_dev_attr_is_visible(struct kobject *kobj,
>  					 struct attribute *attr, int n)
>  {
>  	struct device *dev = kobj_to_dev(kobj);
> +	struct hwmon_device *hdev = to_hwmon_device(dev);
>  
> -	if (to_hwmon_device(dev)->name == NULL)
> +	if (attr == &dev_attr_name.attr && hdev->name == NULL)
> +		return 0;
> +
> +	if (attr == &dev_attr_label.attr && hdev->label == NULL)
>  		return 0;
>  
>  	return attr->mode;
> @@ -89,7 +103,7 @@ static umode_t hwmon_dev_name_is_visible(struct kobject *kobj,
>  
>  static const struct attribute_group hwmon_dev_attr_group = {
>  	.attrs		= hwmon_dev_attrs,
> -	.is_visible	= hwmon_dev_name_is_visible,
> +	.is_visible	= hwmon_dev_attr_is_visible,
>  };
>  
>  static const struct attribute_group *hwmon_dev_attr_groups[] = {
> @@ -117,6 +131,7 @@ static void hwmon_dev_release(struct device *dev)
>  	if (hwdev->group.attrs)
>  		hwmon_free_attrs(hwdev->group.attrs);
>  	kfree(hwdev->groups);
> +	kfree(hwdev->label);
>  	kfree(hwdev);
>  }
>  
> @@ -733,6 +748,7 @@ __hwmon_device_register(struct device *dev, const char *name, void *drvdata,
>  			const struct attribute_group **groups)
>  {
>  	struct hwmon_device *hwdev;
> +	const char *label;
>  	struct device *hdev;
>  	int i, err, id;
>  
> @@ -752,6 +768,18 @@ __hwmon_device_register(struct device *dev, const char *name, void *drvdata,
>  		goto ida_remove;
>  	}
>  
> +	if (device_property_present(dev, "label")) {
> +		err = device_property_read_string(dev, "label", &label);
> +		if (err < 0)
> +			goto free_hwmon;
> +
> +		hwdev->label = kstrdup(label, GFP_KERNEL);
> +		if (hwdev->label == NULL) {
> +			err = -ENOMEM;
> +			goto free_hwmon;

The code after free_hwmon: uses hdev, so 0-day has a point. Please fix.

Guenter

> +		}
> +	}
> +
>  	hdev = &hwdev->dev;
>  
>  	if (chip) {