linux-kernel - Re: [PATCH] hwmon: (w83791d) Make use of hwmon_device_register_with

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Date:   Sat, 4 Feb 2017 15:42:11 -0800
From:   Guenter Roeck <linux@...ck-us.net>
To:     Alexey Khoroshilov <khoroshilov@...ras.ru>,
        Marc Hulsman <m.hulsman@...elft.nl>,
        Jean Delvare <jdelvare@...e.com>
Cc:     linux-hwmon@...r.kernel.org, linux-kernel@...r.kernel.org,
        ldv-project@...uxtesting.org
Subject: Re: [PATCH] hwmon: (w83791d) Make use of
 hwmon_device_register_with_groups

On 02/04/2017 03:12 PM, Alexey Khoroshilov wrote:
> There is no remove of w83791d_group_fanpwm45 sysfs group.
> Fix the problem by switching to hwmon_device_register_with_groups().
>
> Found by Linux Driver Verification project (linuxtesting.org).
>
> Signed-off-by: Alexey Khoroshilov <khoroshilov@...ras.ru>
> ---
>  drivers/hwmon/w83791d.c | 40 +++++++++++++++-------------------------
>  1 file changed, 15 insertions(+), 25 deletions(-)
>
> diff --git a/drivers/hwmon/w83791d.c b/drivers/hwmon/w83791d.c
> index 001df856913f..14a19396785e 100644
> --- a/drivers/hwmon/w83791d.c
> +++ b/drivers/hwmon/w83791d.c
> @@ -1211,7 +1211,7 @@ static DEVICE_ATTR(vrm, S_IRUGO | S_IWUSR, show_vrm_reg, store_vrm_reg);
>  	&sda_temp_beep[X].dev_attr.attr,	\
>  	&sda_temp_alarm[X].dev_attr.attr
>
> -static struct attribute *w83791d_attributes[] = {
> +static struct attribute *w83791d_attrs[] = {
>  	IN_UNIT_ATTRS(0),
>  	IN_UNIT_ATTRS(1),
>  	IN_UNIT_ATTRS(2),
> @@ -1248,16 +1248,14 @@ static struct attribute *w83791d_attributes[] = {
>  	NULL
>  };
>
> -static const struct attribute_group w83791d_group = {
> -	.attrs = w83791d_attributes,
> -};
> +ATTRIBUTE_GROUPS(w83791d);
>
>  /*
>   * Separate group of attributes for fan/pwm 4-5. Their pins can also be
>   * in use for GPIO in which case their sysfs-interface should not be made
>   * available
>   */
> -static struct attribute *w83791d_attributes_fanpwm45[] = {
> +static struct attribute *w83791d_attrs_fanpwm45[] = {
>  	FAN_UNIT_ATTRS(3),
>  	FAN_UNIT_ATTRS(4),
>  	&sda_pwm[3].dev_attr.attr,
> @@ -1266,7 +1264,13 @@ static struct attribute *w83791d_attributes_fanpwm45[] = {
>  };
>
>  static const struct attribute_group w83791d_group_fanpwm45 = {
> -	.attrs = w83791d_attributes_fanpwm45,
> +	.attrs = w83791d_attrs_fanpwm45,
> +};
> +
> +static const struct attribute_group *w83791d_groups_fanpwm45[] = {
> +	&w83791d_group,
> +	&w83791d_group_fanpwm45,
> +	NULL
>  };
>
>  static int w83791d_detect_subclients(struct i2c_client *client)
> @@ -1376,6 +1380,7 @@ static int w83791d_probe(struct i2c_client *client,
>  	struct device *dev = &client->dev;
>  	int i, err;
>  	u8 has_fanpwm45;
> +	const struct attribute_group **groups;
>
>  #ifdef DEBUG
>  	int val1;
> @@ -1406,34 +1411,20 @@ static int w83791d_probe(struct i2c_client *client,
>  	for (i = 0; i < NUMBER_OF_FANIN; i++)
>  		data->fan_min[i] = w83791d_read(client, W83791D_REG_FAN_MIN[i]);
>
> -	/* Register sysfs hooks */
> -	err = sysfs_create_group(&client->dev.kobj, &w83791d_group);
> -	if (err)
> -		goto error3;
> -
>  	/* Check if pins of fan/pwm 4-5 are in use as GPIO */
>  	has_fanpwm45 = w83791d_read(client, W83791D_REG_GPIO) & 0x10;
> -	if (has_fanpwm45) {
> -		err = sysfs_create_group(&client->dev.kobj,
> -					 &w83791d_group_fanpwm45);
> -		if (err)
> -			goto error4;
> -	}
> +	groups = has_fanpwm45 ? w83791d_groups_fanpwm45 : w83791d_groups;
>
>  	/* Everything is ready, now register the working device */
> -	data->hwmon_dev = hwmon_device_register(dev);
> +	data->hwmon_dev = hwmon_device_register_with_groups(dev, "w83791d",
> +							    NULL, groups);

The new API attaches the hwmon attributes to the hwmon device, not to the
i2c device. This means that one has to use dev_get_drvdata() in the
access functions, and store the i2c device in the local data structure
(here: struct w83791d_data). Also, one has to pass the local data
structure as argument to hwmon_device_register_with_groups().
You did not do any of that, which makes me wonder if you tested this
code. Unless I am really missing something, it should crash quite nicely
if you load the driver on a system with this chip and try to access
any of the attributes.

Guenter

>  	if (IS_ERR(data->hwmon_dev)) {
>  		err = PTR_ERR(data->hwmon_dev);
> -		goto error5;
> +		goto error3;
>  	}
>
>  	return 0;
>
> -error5:
> -	if (has_fanpwm45)
> -		sysfs_remove_group(&client->dev.kobj, &w83791d_group_fanpwm45);
> -error4:
> -	sysfs_remove_group(&client->dev.kobj, &w83791d_group);
>  error3:
>  	if (data->lm75[0] != NULL)
>  		i2c_unregister_device(data->lm75[0]);
> @@ -1447,7 +1438,6 @@ static int w83791d_remove(struct i2c_client *client)
>  	struct w83791d_data *data = i2c_get_clientdata(client);
>
>  	hwmon_device_unregister(data->hwmon_dev);
> -	sysfs_remove_group(&client->dev.kobj, &w83791d_group);
>
>  	if (data->lm75[0] != NULL)
>  		i2c_unregister_device(data->lm75[0]);
>