Message-ID: <2419e2ab-25e2-483b-a163-6b4fbfef6866@roeck-us.net>
Date: Tue, 6 Aug 2024 17:32:24 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: Maximilian Luz <luzmaximilian@...il.com>
Cc: Jean Delvare <jdelvare@...e.com>, Hans de Goede <hdegoede@...hat.com>,
 Ivor Wanders <ivor@...nders.net>, linux-kernel@...r.kernel.org,
 linux-hwmon@...r.kernel.org
Subject: Re: [PATCH v2] hwmon: Add thermal sensor driver for Surface
 Aggregator Module

On 8/4/24 16:08, Maximilian Luz wrote:
> Some of the newer Microsoft Surface devices (such as the Surface Book
> 3 and Pro 9) have thermal sensors connected via the Surface Aggregator
> Module (the embedded controller on those devices). Add a basic driver
> to read out the temperature values of those sensors.
> 
> The EC can have up to 16 thermal sensors connected via a single
> sub-device, each providing temperature readings and a label string.
> 
> Link: https://github.com/linux-surface/surface-aggregator-module/issues/59
> Reviewed-by: Hans de Goede <hdegoede@...hat.com>
> Co-developed-by: Ivor Wanders <ivor@...nders.net>
> Signed-off-by: Ivor Wanders <ivor@...nders.net>
> Signed-off-by: Maximilian Luz <luzmaximilian@...il.com>
> 
> ---
> 
> Links:
>   - v1: https://lore.kernel.org/linux-kernel/ee8c39ab-d47a-481d-a19c-1d656519e66d@gmail.com
> 
> Changes in v2:
>   - Drop patch 0003 ("platform/surface: aggregator_registry: Add support
>     for thermal sensors on the Surface Pro 9") as it has already been
>     applied.
>   - Squash patches 0001 ("hwmon: Add thermal sensor driver for Surface
>     Aggregator Module") and 0002 ("hwmon: surface_temp: Add support for
>     sensor names") into a single patch.
>   - Replace usage of WARN_ON() with dev_err().
>   - Fix formatting and (strict) checkpatch complaints.
> 
> ---
>   MAINTAINERS                  |   6 +
>   drivers/hwmon/Kconfig        |  10 ++
>   drivers/hwmon/Makefile       |   1 +
>   drivers/hwmon/surface_temp.c | 235 +++++++++++++++++++++++++++++++++++
>   4 files changed, 252 insertions(+)
>   create mode 100644 drivers/hwmon/surface_temp.c
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 42decde38320..39c61db0169c 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -15200,6 +15200,12 @@ S:	Maintained
>   F:	Documentation/hwmon/surface_fan.rst
>   F:	drivers/hwmon/surface_fan.c
>   
> +MICROSOFT SURFACE SENSOR THERMAL DRIVER
> +M:	Maximilian Luz <luzmaximilian@...il.com>
> +L:	linux-hwmon@...r.kernel.org
> +S:	Maintained
> +F:	drivers/hwmon/surface_temp.c
> +
>   MICROSOFT SURFACE GPE LID SUPPORT DRIVER
>   M:	Maximilian Luz <luzmaximilian@...il.com>
>   L:	platform-driver-x86@...r.kernel.org
> diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> index b60fe2e58ad6..70c6385f0ed6 100644
> --- a/drivers/hwmon/Kconfig
> +++ b/drivers/hwmon/Kconfig
> @@ -2080,6 +2080,16 @@ config SENSORS_SURFACE_FAN
>   
>   	  Select M or Y here, if you want to be able to read the fan's speed.
>   
> +config SENSORS_SURFACE_TEMP
> +	tristate "Microsoft Surface Thermal Sensor Driver"
> +	depends on SURFACE_AGGREGATOR

As the kernel test robot points out, this dependency is wrong.
__ssam_device_driver_register() is only available
if SURFACE_AGGREGATOR_BUS is enabled.

Guenter

> +	help
> +	  Driver for monitoring thermal sensors connected via the Surface
> +	  Aggregator Module (embedded controller) on Microsoft Surface devices.
> +
> +	  This driver can also be built as a module. If so, the module
> +	  will be called surface_temp.
> +
>   config SENSORS_ADC128D818
>   	tristate "Texas Instruments ADC128D818"
>   	depends on I2C
> diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
> index b1c7056c37db..3ce8d6a9202e 100644
> --- a/drivers/hwmon/Makefile
> +++ b/drivers/hwmon/Makefile
> @@ -209,6 +209,7 @@ obj-$(CONFIG_SENSORS_SPARX5)	+= sparx5-temp.o
>   obj-$(CONFIG_SENSORS_SPD5118)	+= spd5118.o
>   obj-$(CONFIG_SENSORS_STTS751)	+= stts751.o
>   obj-$(CONFIG_SENSORS_SURFACE_FAN)+= surface_fan.o
> +obj-$(CONFIG_SENSORS_SURFACE_TEMP)+= surface_temp.o
>   obj-$(CONFIG_SENSORS_SY7636A)	+= sy7636a-hwmon.o
>   obj-$(CONFIG_SENSORS_AMC6821)	+= amc6821.o
>   obj-$(CONFIG_SENSORS_TC74)	+= tc74.o
> diff --git a/drivers/hwmon/surface_temp.c b/drivers/hwmon/surface_temp.c
> new file mode 100644
> index 000000000000..cd21f331f157
> --- /dev/null
> +++ b/drivers/hwmon/surface_temp.c
> @@ -0,0 +1,235 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/*
> + * Thermal sensor subsystem driver for Surface System Aggregator Module (SSAM).
> + *
> + * Copyright (C) 2022-2023 Maximilian Luz <luzmaximilian@...il.com>
> + */
> +
> +#include <linux/bitops.h>
> +#include <linux/hwmon.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/types.h>
> +
> +#include <linux/surface_aggregator/controller.h>
> +#include <linux/surface_aggregator/device.h>
> +
> +/* -- SAM interface. -------------------------------------------------------- */
> +
> +/*
> + * Available sensors are indicated by a 16-bit bitfield, where a 1 marks the
> + * presence of a sensor. So we have at most 16 possible sensors/channels.
> + */
> +#define SSAM_TMP_SENSOR_MAX_COUNT	16
> +
> +/*
> + * All names observed so far are 6 characters long, but there's only
> + * zeros after the name, so perhaps they can be longer. This number reflects
> + * the maximum zero-padded space observed in the returned buffer.
> + */
> +#define SSAM_TMP_SENSOR_NAME_LENGTH	18
> +
> +struct ssam_tmp_get_name_rsp {
> +	__le16 unknown1;
> +	char unknown2;
> +	char name[SSAM_TMP_SENSOR_NAME_LENGTH];
> +} __packed;
> +
> +static_assert(sizeof(struct ssam_tmp_get_name_rsp) == 21);
> +
> +SSAM_DEFINE_SYNC_REQUEST_CL_R(__ssam_tmp_get_available_sensors, __le16, {
> +	.target_category = SSAM_SSH_TC_TMP,
> +	.command_id      = 0x04,
> +});
> +
> +SSAM_DEFINE_SYNC_REQUEST_MD_R(__ssam_tmp_get_temperature, __le16, {
> +	.target_category = SSAM_SSH_TC_TMP,
> +	.command_id      = 0x01,
> +});
> +
> +SSAM_DEFINE_SYNC_REQUEST_MD_R(__ssam_tmp_get_name, struct ssam_tmp_get_name_rsp, {
> +	.target_category = SSAM_SSH_TC_TMP,
> +	.command_id      = 0x0e,
> +});
> +
> +static int ssam_tmp_get_available_sensors(struct ssam_device *sdev, s16 *sensors)
> +{
> +	__le16 sensors_le;
> +	int status;
> +
> +	status = __ssam_tmp_get_available_sensors(sdev, &sensors_le);
> +	if (status)
> +		return status;
> +
> +	*sensors = le16_to_cpu(sensors_le);
> +	return 0;
> +}
> +
> +static int ssam_tmp_get_temperature(struct ssam_device *sdev, u8 iid, long *temperature)
> +{
> +	__le16 temp_le;
> +	int status;
> +
> +	status = __ssam_tmp_get_temperature(sdev->ctrl, sdev->uid.target, iid, &temp_le);
> +	if (status)
> +		return status;
> +
> +	/* Convert 1/10 °K to 1/1000 °C */
> +	*temperature = (le16_to_cpu(temp_le) - 2731) * 100L;
> +	return 0;
> +}
> +
> +static int ssam_tmp_get_name(struct ssam_device *sdev, u8 iid, char *buf, size_t buf_len)
> +{
> +	struct ssam_tmp_get_name_rsp name_rsp;
> +	int status;
> +
> +	status =  __ssam_tmp_get_name(sdev->ctrl, sdev->uid.target, iid, &name_rsp);
> +	if (status)
> +		return status;
> +
> +	/*
> +	 * This should not fail unless the name in the returned struct is not
> +	 * null-terminated or someone changed something in the struct
> +	 * definitions above, since our buffer and struct have the same
> +	 * capacity by design. So if this fails, log an error message. Since
> +	 * the more likely cause is that the returned string isn't
> +	 * null-terminated, we might have received garbage (as opposed to just
> +	 * an incomplete string), so also fail the function.
> +	 */
> +	status = strscpy(buf, name_rsp.name, buf_len);
> +	if (status < 0) {
> +		dev_err(&sdev->dev, "received non-null-terminated sensor name string\n");
> +		return status;
> +	}
> +
> +	return 0;
> +}
> +
> +/* -- Driver.---------------------------------------------------------------- */
> +
> +struct ssam_temp {
> +	struct ssam_device *sdev;
> +	s16 sensors;
> +	char names[SSAM_TMP_SENSOR_MAX_COUNT][SSAM_TMP_SENSOR_NAME_LENGTH];
> +};
> +
> +static umode_t ssam_temp_hwmon_is_visible(const void *data,
> +					  enum hwmon_sensor_types type,
> +					  u32 attr, int channel)
> +{
> +	const struct ssam_temp *ssam_temp = data;
> +
> +	if (!(ssam_temp->sensors & BIT(channel)))
> +		return 0;
> +
> +	return 0444;
> +}
> +
> +static int ssam_temp_hwmon_read(struct device *dev,
> +				enum hwmon_sensor_types type,
> +				u32 attr, int channel, long *value)
> +{
> +	const struct ssam_temp *ssam_temp = dev_get_drvdata(dev);
> +
> +	return ssam_tmp_get_temperature(ssam_temp->sdev, channel + 1, value);
> +}
> +
> +static int ssam_temp_hwmon_read_string(struct device *dev,
> +				       enum hwmon_sensor_types type,
> +				       u32 attr, int channel, const char **str)
> +{
> +	const struct ssam_temp *ssam_temp = dev_get_drvdata(dev);
> +
> +	*str = ssam_temp->names[channel];
> +	return 0;
> +}
> +
> +static const struct hwmon_channel_info * const ssam_temp_hwmon_info[] = {
> +	HWMON_CHANNEL_INFO(chip,
> +			   HWMON_C_REGISTER_TZ),
> +	HWMON_CHANNEL_INFO(temp,
> +			   HWMON_T_INPUT | HWMON_T_LABEL,
> +			   HWMON_T_INPUT | HWMON_T_LABEL,
> +			   HWMON_T_INPUT | HWMON_T_LABEL,
> +			   HWMON_T_INPUT | HWMON_T_LABEL,
> +			   HWMON_T_INPUT | HWMON_T_LABEL,
> +			   HWMON_T_INPUT | HWMON_T_LABEL,
> +			   HWMON_T_INPUT | HWMON_T_LABEL,
> +			   HWMON_T_INPUT | HWMON_T_LABEL,
> +			   HWMON_T_INPUT | HWMON_T_LABEL,
> +			   HWMON_T_INPUT | HWMON_T_LABEL,
> +			   HWMON_T_INPUT | HWMON_T_LABEL,
> +			   HWMON_T_INPUT | HWMON_T_LABEL,
> +			   HWMON_T_INPUT | HWMON_T_LABEL,
> +			   HWMON_T_INPUT | HWMON_T_LABEL,
> +			   HWMON_T_INPUT | HWMON_T_LABEL,
> +			   HWMON_T_INPUT | HWMON_T_LABEL),
> +	NULL
> +};
> +
> +static const struct hwmon_ops ssam_temp_hwmon_ops = {
> +	.is_visible = ssam_temp_hwmon_is_visible,
> +	.read = ssam_temp_hwmon_read,
> +	.read_string = ssam_temp_hwmon_read_string,
> +};
> +
> +static const struct hwmon_chip_info ssam_temp_hwmon_chip_info = {
> +	.ops = &ssam_temp_hwmon_ops,
> +	.info = ssam_temp_hwmon_info,
> +};
> +
> +static int ssam_temp_probe(struct ssam_device *sdev)
> +{
> +	struct ssam_temp *ssam_temp;
> +	struct device *hwmon_dev;
> +	s16 sensors;
> +	int channel;
> +	int status;
> +
> +	status = ssam_tmp_get_available_sensors(sdev, &sensors);
> +	if (status)
> +		return status;
> +
> +	ssam_temp = devm_kzalloc(&sdev->dev, sizeof(*ssam_temp), GFP_KERNEL);
> +	if (!ssam_temp)
> +		return -ENOMEM;
> +
> +	ssam_temp->sdev = sdev;
> +	ssam_temp->sensors = sensors;
> +
> +	/* Retrieve the name for each available sensor. */
> +	for (channel = 0; channel < SSAM_TMP_SENSOR_MAX_COUNT; channel++) {
> +		if (!(sensors & BIT(channel)))
> +			continue;
> +
> +		status = ssam_tmp_get_name(sdev, channel + 1, ssam_temp->names[channel],
> +					   SSAM_TMP_SENSOR_NAME_LENGTH);
> +		if (status)
> +			return status;
> +	}
> +
> +	hwmon_dev = devm_hwmon_device_register_with_info(&sdev->dev, "surface_thermal", ssam_temp,
> +							 &ssam_temp_hwmon_chip_info, NULL);
> +	return PTR_ERR_OR_ZERO(hwmon_dev);
> +}
> +
> +static const struct ssam_device_id ssam_temp_match[] = {
> +	{ SSAM_SDEV(TMP, SAM, 0x00, 0x02) },
> +	{ },
> +};
> +MODULE_DEVICE_TABLE(ssam, ssam_temp_match);
> +
> +static struct ssam_device_driver ssam_temp = {
> +	.probe = ssam_temp_probe,
> +	.match_table = ssam_temp_match,
> +	.driver = {
> +		.name = "surface_temp",
> +		.probe_type = PROBE_PREFER_ASYNCHRONOUS,
> +	},
> +};
> +module_ssam_device_driver(ssam_temp);
> +
> +MODULE_AUTHOR("Maximilian Luz <luzmaximilian@...il.com>");
> +MODULE_DESCRIPTION("Thermal sensor subsystem driver for Surface System Aggregator Module");
> +MODULE_LICENSE("GPL");

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