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Sender: Guenter Roeck <groeck7@gmail.com>
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Date:   Sun, 10 Apr 2022 06:43:22 -0700
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Subject: Re: [PATCH] hwmon: (dell-smm) Add cooling device support
Content-Language: en-US
To:     =?UTF-8?Q?Pali_Roh=c3=a1r?= <pali@kernel.org>,
        Armin Wolf <W_Armin@gmx.de>
Cc:     jdelvare@suse.com, linux-hwmon@vger.kernel.org,
        linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org
References: <20220330163324.572437-1-W_Armin@gmx.de>
 <757b30ef-e250-063f-7523-030f56b1d0b8@gmx.de>
 <20220410100845.2isvctcw643yfp7n@pali>
From:   Guenter Roeck <linux@roeck-us.net>
In-Reply-To: <20220410100845.2isvctcw643yfp7n@pali>
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On 4/10/22 03:08, Pali Rohár wrote:
> On Saturday 09 April 2022 17:33:48 Armin Wolf wrote:
>> Am 30.03.22 um 18:33 schrieb Armin Wolf:
>>
>>> Until now, only the temperature sensors where exported thru
>>> the thermal subsystem. Export the fans as "dell-smm-fan[1-3]" too
>>> to make them available as cooling devices.
>>> Also update Documentation.
>>>
>>> Signed-off-by: Armin Wolf <W_Armin@gmx.de>
>>> ---
>>>    Documentation/hwmon/dell-smm-hwmon.rst |  7 ++
>>>    drivers/hwmon/Kconfig                  |  1 +
>>>    drivers/hwmon/dell-smm-hwmon.c         | 94 +++++++++++++++++++++++++-
>>>    3 files changed, 99 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/Documentation/hwmon/dell-smm-hwmon.rst b/Documentation/hwmon/dell-smm-hwmon.rst
>>> index d3323a96665d..41839b7de2c1 100644
>>> --- a/Documentation/hwmon/dell-smm-hwmon.rst
>>> +++ b/Documentation/hwmon/dell-smm-hwmon.rst
>>> @@ -86,6 +86,13 @@ probe the BIOS on your machine and discover the appropriate codes.
>>>
>>>    Again, when you find new codes, we'd be happy to have your patches!
>>>
>>> +``thermal`` interface
>>> +---------------------------
>>> +
>>> +The driver also exports the fans as thermal cooling devices with
>>> +``type`` set to ``dell-smm-fan[1-3]``. This allows for easy fan control
>>> +using one of the thermal governors.
>>> +
>>>    Module parameters
>>>    -----------------
>>>
>>> diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
>>> index 9ab4e9b3d27b..1175b8e38c45 100644
>>> --- a/drivers/hwmon/Kconfig
>>> +++ b/drivers/hwmon/Kconfig
>>> @@ -498,6 +498,7 @@ config SENSORS_DS1621
>>>    config SENSORS_DELL_SMM
>>>    	tristate "Dell laptop SMM BIOS hwmon driver"
>>>    	depends on X86
>>> +	imply THERMAL
>>>    	help
>>>    	  This hwmon driver adds support for reporting temperature of different
>>>    	  sensors and controls the fans on Dell laptops via System Management
>>> diff --git a/drivers/hwmon/dell-smm-hwmon.c b/drivers/hwmon/dell-smm-hwmon.c
>>> index 84cb1ede7bc0..0c29386f4bd3 100644
>>> --- a/drivers/hwmon/dell-smm-hwmon.c
>>> +++ b/drivers/hwmon/dell-smm-hwmon.c
>>> @@ -21,6 +21,7 @@
>>>    #include <linux/errno.h>
>>>    #include <linux/hwmon.h>
>>>    #include <linux/init.h>
>>> +#include <linux/kconfig.h>
>>>    #include <linux/kernel.h>
>>>    #include <linux/module.h>
>>>    #include <linux/mutex.h>
>>> @@ -29,6 +30,7 @@
>>>    #include <linux/seq_file.h>
>>>    #include <linux/string.h>
>>>    #include <linux/smp.h>
>>> +#include <linux/thermal.h>
>>>    #include <linux/types.h>
>>>    #include <linux/uaccess.h>
>>>
>>> @@ -80,6 +82,11 @@ struct dell_smm_data {
>>>    	int *fan_nominal_speed[DELL_SMM_NO_FANS];
>>>    };
>>>
>>> +struct dell_smm_cooling_data {
>>> +	u8 fan_num;
>>> +	struct dell_smm_data *data;
>>> +};
>>> +
>>>    MODULE_AUTHOR("Massimo Dal Zotto (dz@debian.org)");
>>>    MODULE_AUTHOR("Pali Rohár <pali@kernel.org>");
>>>    MODULE_DESCRIPTION("Dell laptop SMM BIOS hwmon driver");
>>> @@ -638,9 +645,50 @@ static void __init i8k_init_procfs(struct device *dev)
>>>
>>>    #endif
>>>
>>> -/*
>>> - * Hwmon interface
>>> - */
>>> +static int dell_smm_get_max_state(struct thermal_cooling_device *dev, unsigned long *state)
>>> +{
>>> +	struct dell_smm_cooling_data *cdata = dev->devdata;
>>> +
>>> +	*state = cdata->data->i8k_fan_max;
>>> +
>>> +	return 0;
>>> +}
>>> +
>>> +static int dell_smm_get_cur_state(struct thermal_cooling_device *dev, unsigned long *state)
>>> +{
>>> +	struct dell_smm_cooling_data *cdata = dev->devdata;
>>> +	int ret;
>>> +
>>> +	ret = i8k_get_fan_status(cdata->data, cdata->fan_num);
>>> +	if (ret < 0)
>>> +		return ret;
>>> +
>>> +	*state = ret;
>>> +
>>> +	return 0;
>>> +}
>>> +
>>> +static int dell_smm_set_cur_state(struct thermal_cooling_device *dev, unsigned long state)
>>> +{
>>> +	struct dell_smm_cooling_data *cdata = dev->devdata;
>>> +	struct dell_smm_data *data = cdata->data;
>>> +	int ret;
>>> +
>>> +	if (state > data->i8k_fan_max)
>>> +		return -EINVAL;
>>> +
>>> +	mutex_lock(&data->i8k_mutex);
>>> +	ret = i8k_set_fan(data, cdata->fan_num, (int)state);
>>> +	mutex_unlock(&data->i8k_mutex);
>>> +
>>> +	return ret;
>>> +}
>>> +
>>> +static const struct thermal_cooling_device_ops dell_smm_cooling_ops = {
>>> +	.get_max_state = dell_smm_get_max_state,
>>> +	.get_cur_state = dell_smm_get_cur_state,
>>> +	.set_cur_state = dell_smm_set_cur_state,
>>> +};
>>>
>>>    static umode_t dell_smm_is_visible(const void *drvdata, enum hwmon_sensor_types type, u32 attr,
>>>    				   int channel)
>>> @@ -941,6 +989,37 @@ static const struct hwmon_chip_info dell_smm_chip_info = {
>>>    	.info = dell_smm_info,
>>>    };
>>>
>>> +static int __init dell_smm_init_cdev(struct device *dev, u8 fan_num)
>>> +{
>>> +	struct dell_smm_data *data = dev_get_drvdata(dev);
>>> +	struct thermal_cooling_device *cdev;
>>> +	struct dell_smm_cooling_data *cdata;
>>> +	int ret = 0;
>>> +	char *name;
>>> +
>>> +	name = kasprintf(GFP_KERNEL, "dell-smm-fan%u", fan_num + 1);
>>> +	if (!name)
>>> +		return -ENOMEM;
>>> +
>>> +	cdata = devm_kmalloc(dev, sizeof(*cdata), GFP_KERNEL);
>>> +	if (cdata) {
>>> +		cdata->fan_num = fan_num;
>>> +		cdata->data = data;
>>> +		cdev = devm_thermal_of_cooling_device_register(dev, NULL, name, cdata,
>>> +							       &dell_smm_cooling_ops);
>>> +		if (IS_ERR(cdev)) {
>>> +			devm_kfree(dev, cdata);
>>> +			ret = PTR_ERR(cdev);
>>> +		}
>>> +	} else {
>>> +		ret = -ENOMEM;
>>> +	}
>>> +
>>> +	kfree(name);
>>> +
>>> +	return ret;
>>> +}
>>> +
>>>    static int __init dell_smm_init_hwmon(struct device *dev)
>>>    {
>>>    	struct dell_smm_data *data = dev_get_drvdata(dev);
>>> @@ -967,6 +1046,15 @@ static int __init dell_smm_init_hwmon(struct device *dev)
>>>    			continue;
>>>
>>>    		data->fan[i] = true;
>>> +
>>> +		/* the cooling device it not critical, ignore failures */
>>> +		if (IS_REACHABLE(CONFIG_THERMAL)) {
>>> +			err = dell_smm_init_cdev(dev, i);
>>> +			if (err < 0)
>>> +				dev_err(dev, "Failed to register cooling device for fan %u\n",
>>> +					i + 1);
>>> +		}
>>> +
>>>    		data->fan_nominal_speed[i] = devm_kmalloc_array(dev, data->i8k_fan_max + 1,
>>>    								sizeof(*data->fan_nominal_speed[i]),
>>>    								GFP_KERNEL);
>>> --
>>> 2.30.2
>>>
>> Any thoughts on this? I tested it on a Dell Inspiron 3505, so i can prove it works.
> 
> Hello! If hwmon maintainers are happy with this approach and this new
> API then I'm fine with it. Maybe one thing to discuss, should not be
> dell_smm_init_cdev() fatal on error?

"the cooling device it not critical, ignore failures"

Besides the misspelling - if it is not fatal, the code should not use
dev_err() but dev_warning(). Other than that I am ok as well.

Guenter