[PATCH V3 0/1] platform/x86: Add BIOS Dynamic SAR driver for Intel M.2 Modem

[PATCH V3 0/1] platform/x86: Add BIOS Dynamic SAR driver for Intel M.2 Modem

[Shravan S]

SAR (Specific Absorption Rate) driver is a host driver implemented for Linux
or chrome platform to limit the exposure of human body to RF frequency by informing
the Intel M.2 modem to regulate the RF power based on SAR data obtained from the sensors
captured in the BIOS. ACPI interface exposes this data from the BIOS to SAR driver. The
front end application in userspace ( eg: Modem Manager) will interact with SAR driver 
to obtain information like the device mode (Example: tablets, laptops, etx), Antenna index,
baseband index, SAR table index and use available communication like MBIM interface to enable
data communication to modem for RF power regulation.

The BIOS gets notified about device mode changes through Sensor Driver. This information is 
given to a (newly created) WWAN ACPI function driver when there is a device mode change. 
The driver then uses a _DSM method to retrieve the required information from BIOS. 
This information is then forwarded to the User-space using the sysfs_notify interface.
A lookup table is maintained inside the BIOS which suggests the SAR Table index and Antenna 
Tuner Table Index values for individual device modes.

The SAR parameters to be used on the Modem differs for each Regulatory Mode like FCC, CE and ISED.
Hence, the SAR parameters are stored separately in the SMBIOS table in the OEM BIOS, 
for each of the Regulatory mode. Regulatory modes will be different based on the region and network
available in that region.

Hence the entire SAR functionality handling is divided into 2 parts:

•	A ACPI function driver implemented that uses a dedicated ACPI node for WWAN device.
    Sends notifications whenever there is change in Device Mode. (each OEM has different mechanism
    of updating this DEVICE Mode info). This is notified to User-space applications using 
    the sysfs_notify interface.
•	WWAN Device Service listens for sysfs_notify messages and reads the sysfs data and routes them 
	to Modem using MBIM.


Shravan S (1):
  platform/x86: Add BIOS Dynamic SAR driver for Intel M.2 Modem

 .../networking/device_drivers/wwan/index.rst  |   9 +-
 .../device_drivers/wwan/intc_sar.rst          |  60 ++++
 drivers/platform/x86/Kconfig                  |  12 +
 drivers/platform/x86/Makefile                 |   1 +
 drivers/platform/x86/intel-sar.c              | 326 ++++++++++++++++++
 include/linux/platform_data/x86/intel-sar.h   |  89 +++++
 6 files changed, 493 insertions(+), 4 deletions(-)
 create mode 100644 Documentation/networking/device_drivers/wwan/intc_sar.rst
 create mode 100644 drivers/platform/x86/intel-sar.c
 create mode 100644 include/linux/platform_data/x86/intel-sar.h


base-commit: d936eb23874433caa3e3d841cfa16f5434b85dcf
-- 
2.17.1

[PATCH V3 1/1] platform/x86: Add BIOS Dynamic SAR driver for Intel M.2 Modem

[Shravan S]

BIOS SAR (Specific Absorption Rate) driver for RF power regulation on Intel M.2 Modem.
Limits the exposure of human body to RF frequencies.
Uses ACPI to communicate to BIOS to retrieve SAR information data.
Uses Sysfs to communicate this data to userspace via read and notify.
Userspace will further use MBIM interface to enable data communication to modem.

Signed-off-by: Shravan S <s.shravan@intel.com>
---
V3 :
* Changes to the remove netlink and introduce sysfs to communicate to Userspace via notify
* Handled review comments by changing ioctl calls to sysfs
* "sar" name change for platform_device_id to "intc1092"
* sar_init and sar_exit is modified as per review to minimal initialization
* logging reduction and cleanup based on reviews.

---
 .../networking/device_drivers/wwan/index.rst  |   9 +-
 .../device_drivers/wwan/intc_sar.rst          |  60 ++++
 drivers/platform/x86/Kconfig                  |  12 +
 drivers/platform/x86/Makefile                 |   1 +
 drivers/platform/x86/intel-sar.c              | 326 ++++++++++++++++++
 include/linux/platform_data/x86/intel-sar.h   |  89 +++++
 6 files changed, 493 insertions(+), 4 deletions(-)
 create mode 100644 Documentation/networking/device_drivers/wwan/intc_sar.rst
 create mode 100644 drivers/platform/x86/intel-sar.c
 create mode 100644 include/linux/platform_data/x86/intel-sar.h

diff --git a/Documentation/networking/device_drivers/wwan/index.rst b/Documentation/networking/device_drivers/wwan/index.rst
index 1cb8c7371401..93dfd89f76e8 100644
--- a/Documentation/networking/device_drivers/wwan/index.rst
+++ b/Documentation/networking/device_drivers/wwan/index.rst
@@ -1,14 +1,15 @@
-.. SPDX-License-Identifier: GPL-2.0-only
+.. SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
 
-WWAN Device Drivers
-===================
+Classic WAN Device Drivers
+==========================
 
 Contents:
 
 .. toctree::
    :maxdepth: 2
 
-   iosm
+   z8530book
+   intc_sar
 
 .. only::  subproject and html
 
diff --git a/Documentation/networking/device_drivers/wwan/intc_sar.rst b/Documentation/networking/device_drivers/wwan/intc_sar.rst
new file mode 100644
index 000000000000..7319d6e593ed
--- /dev/null
+++ b/Documentation/networking/device_drivers/wwan/intc_sar.rst
@@ -0,0 +1,60 @@
+.. SPDX-License-Identifier: GPL-2.0-only
+
+.. Copyright (C) 2020-21 Intel Corporation
+
+.. _INTEL_SAR_driver_doc:
+
+===========================================
+BIOS Dynamic SAR driver for Intel M.2 Modem
+===========================================
+SAR (Specific Absorption Rate) driver is a host driver implemented for Linux
+or chrome platform to limit the exposure of human body to RF frequency by
+informing the Intel M.2 modem to regulate the RF power based on SAR data
+obtained from the sensors captured in the BIOS.
+
+Basic usage
+===========
+ACPI interface exposes this data from the BIOS to SAR driver. The front end
+application in userspace ( eg: Modem Manager) will interact with SAR driver 
+to obtain information like the device mode (Example: tablets, laptops, etx),
+Antenna index, baseband index, SAR table index and use available communication
+like MBIM interface to enable data communication to modem for power regulation.
+
+Applications to carry out below required actions for establishing connection
+with driver for data communication with the SAR driver:
+- open the sysfs file for communication
+- read the data to get the information
+- get notification from sysfs if data is changed
+- write into sysfs to change regulatory mode.
+
+Management application development
+==================================
+The driver and userspace interfaces are described below.
+
+sysfs channel for communication to userspace
+--------------------------------------------
+
+/sys/bus/platform/devices/INTC1092:00/intc_reg
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+The driver exposes an sysfs entry in the kernel which is used for sending and
+receiving regulatory information. The regulatory modes are depending on network.
+FCC(0), CE(1), ISED(2)
+
+/sys/bus/platform/devices/INTC1092:00/intc_reg write()
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+The regulatory modes should not exceed the allowed reguulatory worldwide.
+
+/sys/bus/platform/devices/INTC1092:00/intc_reg read()
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+The application can read the current regulatory mode that is set in the
+driver.
+
+/sys/bus/platform/devices/INTC1092:00/intc_data
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+The driver exposes an sysfs entry in the kernel which is used for receiving
+information sent by BIOS.
+
+/sys/bus/platform/devices/INTC1092:00/intc_data read()
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+The SAR index, Band index and Antenna index along with the device modes are
+obtained from this sysfs.
diff --git a/drivers/platform/x86/Kconfig b/drivers/platform/x86/Kconfig
index 7d385c3b2239..f3abf935a976 100644
--- a/drivers/platform/x86/Kconfig
+++ b/drivers/platform/x86/Kconfig
@@ -1306,6 +1306,18 @@ config INTEL_TELEMETRY
 	  directly via debugfs files. Various tools may use
 	  this interface for SoC state monitoring.
 
+config INTEL_SAR
+	tristate "Intel Specific Absorption Rate Driver"
+	depends on ACPI
+	help
+	  This driver limit the exposure of human body to RF frequency by informing
+	  the Intel M.2 modem to regulate the RF power based on SAR data obtained
+	  from the sensors captured in the BIOS. ACPI interface exposes this data
+	  from the BIOS to SAR driver. The front end application in userspace
+	  will interact with SAR driver to obtain information like the device mode,
+	  Antenna index, baseband index, SAR table index and use available communication
+	  like MBIM interface to enable data communication to modem for RF power regulation.
+
 endif # X86_PLATFORM_DEVICES
 
 config PMC_ATOM
diff --git a/drivers/platform/x86/Makefile b/drivers/platform/x86/Makefile
index 7ee369aab10d..3610ab7a12df 100644
--- a/drivers/platform/x86/Makefile
+++ b/drivers/platform/x86/Makefile
@@ -123,6 +123,7 @@ obj-$(CONFIG_INTEL_SMARTCONNECT)		+= intel-smartconnect.o
 obj-$(CONFIG_INTEL_SPEED_SELECT_INTERFACE)	+= intel_speed_select_if/
 obj-$(CONFIG_INTEL_TURBO_MAX_3)			+= intel_turbo_max_3.o
 obj-$(CONFIG_INTEL_UNCORE_FREQ_CONTROL)		+= intel-uncore-frequency.o
+obj-$(CONFIG_INTEL_SAR)				+= intel-sar.o
 
 # Intel PMIC / PMC / P-Unit devices
 obj-$(CONFIG_INTEL_BXTWC_PMIC_TMU)	+= intel_bxtwc_tmu.o
diff --git a/drivers/platform/x86/intel-sar.c b/drivers/platform/x86/intel-sar.c
new file mode 100644
index 000000000000..9906eb4d79a7
--- /dev/null
+++ b/drivers/platform/x86/intel-sar.c
@@ -0,0 +1,326 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Intel Corporation - ACPI for Specific Absorption Rate
+ * Copyright (c) 2021, Intel Corporation.
+ */
+
+#include <asm/errno.h>
+#include <linux/acpi.h>
+#include <linux/kobject.h>
+#include <linux/platform_data/x86/intel-sar.h>
+#include <linux/platform_device.h>
+#include <linux/sysfs.h>
+
+/**
+ * get_int_value - Retrieve Integer values from ACPI Object
+ * Value of the integer from the object of ACPI is obtained.
+ * @obj: acpi_object pointer which has the integer value
+ * @out: output pointer will get integer value
+ * returns 0 on success
+ */
+static int get_int_value(union acpi_object *obj, int *out)
+{
+	if (obj && obj->type == ACPI_TYPE_INTEGER) {
+		*out = (int)obj->integer.value;
+		return 0;
+	} else {
+		return -EFAULT;
+	}
+}
+
+/**
+ * update_sar_data - sar data is updated based on reg_value
+ * sar_data is updated based on regulatory value
+ * context->reg_value will never exceed MAX_REGULATORY
+ * @context: context pointer used for data
+ */
+static void update_sar_data(struct wwan_sar_context *context)
+{
+	struct wwan_device_mode_configuration *config =
+	&context->config_data[context->reg_value];
+
+	if (config->device_mode_info &&
+	    context->sar_data.device_mode <= config->total_dev_mode) {
+		struct wwan_device_mode_info *dev_mode =
+		&config->device_mode_info[context->sar_data.device_mode];
+		context->sar_data.antennatable_index = dev_mode->antennatable_index;
+		context->sar_data.bandtable_index = dev_mode->bandtable_index;
+		context->sar_data.sartable_index = dev_mode->sartable_index;
+	}
+}
+
+/**
+ * parse_package - parse package for SAR
+ * @context: context pointer used for data
+ * @item : acpi_object ptr
+ * returns if success or error
+ */
+static acpi_status parse_package(struct wwan_sar_context *context, union acpi_object *item)
+{
+	int value = 0, itr = 0, reg = 0;
+	union acpi_object *num;
+	struct wwan_device_mode_configuration *data;
+
+	num = &item->package.elements[0];
+	if (get_int_value(num, &value) == 0) {
+		if (value >= 0 && value < MAX_REGULATORY)
+			reg = value;
+		else
+			return AE_ERROR;
+	}
+	data = &context->config_data[reg];
+	if (data->total_dev_mode > MAX_DEV_MODES)
+		return AE_ERROR;
+	data->device_mode_info =
+	kmalloc_array(data->total_dev_mode, sizeof(struct wwan_device_mode_info), GFP_KERNEL);
+	if (!data->device_mode_info) {
+		pr_err("Cannot allocate memory in kernel\n");
+		return AE_ERROR;
+	}
+	for (itr = 0; itr < data->total_dev_mode; itr++) {
+		if (itr + 1 == item->package.count)
+			break;
+		num = &item->package.elements[itr + 1];
+		if (num->type != ACPI_TYPE_PACKAGE)
+			continue;
+		if (num->package.count < TOTAL_DATA)
+			break;
+		if (get_int_value(&num->package.elements[0], &value) == 0)
+			data->device_mode_info[itr].device_mode = value;
+		if (get_int_value(&num->package.elements[1], &value) == 0)
+			data->device_mode_info[itr].bandtable_index = value;
+		if (get_int_value(&num->package.elements[2], &value) == 0)
+			data->device_mode_info[itr].antennatable_index = value;
+		if (get_int_value(&num->package.elements[3], &value) == 0)
+			data->device_mode_info[itr].sartable_index = value;
+	}
+	return AE_OK;
+}
+
+/**
+ * sar_module_probe - Extraction of information from BIOS via DSM calls
+ * Retrieve all values related to device mode, SAR Table index,
+ * Antenna Table index, Band Table index
+ * @device: ACPI device for which to retrieve the data
+ * Returns AE_OK on success
+ */
+static acpi_status sar_module_probe(struct platform_device *device)
+{
+	acpi_status status = AE_OK;
+	union acpi_object *out;
+	u32 rev = 0;
+	int value = 0;
+	struct wwan_sar_context *context = dev_get_drvdata(&device->dev);
+
+	pr_alert("%s Triggered\n", __func__);
+	out = acpi_evaluate_dsm(context->handle, &context->guid, rev,
+				COMMAND_ID_DEV_MODE, NULL);
+	if (get_int_value(out, &value) == 0) {
+		context->sar_data.device_mode = value;
+	} else {
+		pr_err("%s: Cmd:%d Failed\n", __func__, COMMAND_ID_DEV_MODE);
+		ACPI_FREE(out);
+		return AE_ERROR;
+	}
+	ACPI_FREE(out);
+	dev_set_drvdata(&device->dev, context);
+	sysfs_notify(context->sar_kobject, NULL, SYSFS_DATANAME);
+	return status;
+}
+
+static const struct acpi_device_id sar_device_ids[] = {
+	{ "INTC1092", 0},
+	{ "", 0},
+};
+
+MODULE_DEVICE_TABLE(acpi, sar_device_ids);
+
+static const struct platform_device_id sar_device_table[] = {
+	{"intc1092", 0},
+	{},
+};
+
+static ssize_t intc_data_show(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	unsigned long ret = 0;
+	struct wwan_sar_context *context = dev_get_drvdata(dev);
+
+	ret = sprintf(buf, "%d %d %d %d\n", context->sar_data.device_mode,
+		      context->sar_data.bandtable_index,
+		      context->sar_data.antennatable_index,
+		      context->sar_data.sartable_index);
+	return ret;
+}
+
+static ssize_t intc_reg_show(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	unsigned long ret = 0;
+	struct wwan_sar_context *context = dev_get_drvdata(dev);
+
+	ret = sprintf(buf, "%d\n", context->reg_value);
+	return ret;
+}
+
+static ssize_t intc_reg_store(struct device *dev, struct device_attribute *attr,
+			      const char *buf, size_t count)
+{
+	int value = 0, read = 0;
+	struct wwan_sar_context *context = dev_get_drvdata(dev);
+
+	if (!count) {
+		pr_err("%s count = %d", __func__, (int)count);
+		return -EFAULT;
+	}
+	read = sscanf(buf, "%u", &value);
+	if (read <= 0) {
+		pr_alert("%s Not a integer", __func__);
+		return -EFAULT;
+	}
+	if (value >= 0 && value < MAX_REGULATORY) {
+		context->reg_value = value;
+		update_sar_data(context);
+		dev_set_drvdata(dev, context);
+		sysfs_notify(context->sar_kobject, NULL, SYSFS_DATANAME);
+	}
+	return count;
+}
+
+static DEVICE_ATTR_RO(intc_data);
+static DEVICE_ATTR_RW(intc_reg);
+
+static struct attribute *intcsar_attrs[] = {
+	&dev_attr_intc_data.attr,
+	&dev_attr_intc_reg.attr,
+	NULL
+};
+
+static struct attribute_group intcsar_group = {
+	.attrs = intcsar_attrs,
+};
+
+static void sar_notify(acpi_handle handle, u32 event, void *data)
+{
+	struct platform_device *device = data;
+
+	if (event == SAR_EVENT) {
+		if (sar_module_probe(device) != AE_OK)
+			pr_err("sar_module_probe error");
+	}
+}
+
+static int sar_probe(struct platform_device *device)
+{
+	int result = 0;
+	struct wwan_sar_context *context;
+	union acpi_object *out, *item, req;
+	acpi_status status = AE_OK;
+	u32 rev = 0, reg = 0;
+	int value = 0;
+
+	context = kmalloc(sizeof(*context), GFP_KERNEL);
+	if (!context)
+		return -ENOMEM;
+	memset(context, 0, sizeof(struct wwan_sar_context));
+	result = sysfs_create_group(&device->dev.kobj, &intcsar_group);
+	if (result) {
+		pr_err("sysfs creation failed\n");
+		goto r_free;
+	}
+	context->sar_kobject = &device->dev.kobj;
+	context->sar_device = device;
+	dev_set_drvdata(&device->dev, context);
+	if (guid_parse(SAR_DSM_UUID, &context->guid)) {
+		pr_err("%s: UUID error\n", __func__);
+		goto r_sys;
+	}
+	context->handle = ACPI_HANDLE(&device->dev);
+	for (reg = 0; reg < MAX_REGULATORY; reg++) {
+		req.type = ACPI_TYPE_INTEGER;
+		req.integer.value = reg;
+		out = acpi_evaluate_dsm(context->handle, &context->guid, rev,
+					COMMAND_ID_CONFIG_TABLE, &req);
+		if (!out) {
+			pr_err("%s: Cmd:%d Failed\n", __func__, COMMAND_ID_CONFIG_TABLE);
+			continue;
+		}
+		if (out->type == ACPI_TYPE_PACKAGE && out->package.count >= 3) {
+			item = &out->package.elements[0];
+			if (get_int_value(item, &value) == 0)
+				context->config_data[reg].version = value;
+			item = &out->package.elements[1];
+			if (get_int_value(item, &value) == 0)
+				context->config_data[reg].total_dev_mode = value;
+			if (context->config_data[reg].total_dev_mode <= 0 &&
+			    context->config_data[reg].total_dev_mode >
+				MAX_DEV_MODES) {
+				pr_err("total_dev_mode is not within range : %d\n",
+				       context->config_data[reg].total_dev_mode);
+				ACPI_FREE(out);
+				continue;
+			}
+			item = &out->package.elements[2];
+			if (item->type == ACPI_TYPE_PACKAGE && item->package.count > 0)
+				status = parse_package(context, item);
+			else
+				status = AE_ERROR;
+			if (status != AE_OK) {
+				ACPI_FREE(out);
+				continue;
+			}
+		}
+		ACPI_FREE(out);
+	}
+	update_sar_data(context);
+	if (sar_module_probe(device) != AE_OK) {
+		pr_err("Failed sar_module_probe\n");
+		goto r_sys;
+	}
+	if (acpi_install_notify_handler(ACPI_HANDLE(&device->dev), ACPI_DEVICE_NOTIFY,
+					sar_notify, (void *)device) != AE_OK) {
+		pr_err("Failed acpi_install_notify_handler\n");
+		goto r_sys;
+	}
+	return 0;
+
+r_sys:
+	sysfs_remove_group(&device->dev.kobj, &intcsar_group);
+r_free:
+	kfree(context);
+	return -1;
+}
+
+static int sar_remove(struct platform_device *device)
+{
+	struct wwan_sar_context *context = dev_get_drvdata(&device->dev);
+	int reg = 0;
+
+	acpi_remove_notify_handler(ACPI_HANDLE(&device->dev),
+				   ACPI_DEVICE_NOTIFY, sar_notify);
+	sysfs_remove_group(&device->dev.kobj, &intcsar_group);
+	for (reg = 0; reg < MAX_REGULATORY; reg++) {
+		kfree(context->config_data[reg].device_mode_info);
+		context->config_data[reg].device_mode_info = NULL;
+	}
+	kfree(context);
+	return 0;
+}
+
+MODULE_DEVICE_TABLE(platform, sar_device_table);
+
+static struct platform_driver sar_driver = {
+	.probe = sar_probe,
+	.remove = sar_remove,
+	.driver = {
+			.name = DRVNAME,
+			.owner = THIS_MODULE,
+			/* FOR ACPI HANDLING */
+			.acpi_match_table = ACPI_PTR(sar_device_ids),
+			},
+	.id_table = sar_device_table,
+};
+
+module_platform_driver(sar_driver);
+
+MODULE_LICENSE("GPL v2");
+MODULE_DESCRIPTION("Platform device driver for INTEL MODEM BIOS SAR");
+MODULE_AUTHOR("Shravan S <s.shravan@intel.com>");
diff --git a/include/linux/platform_data/x86/intel-sar.h b/include/linux/platform_data/x86/intel-sar.h
new file mode 100644
index 000000000000..6e2ac93a3ebc
--- /dev/null
+++ b/include/linux/platform_data/x86/intel-sar.h
@@ -0,0 +1,89 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Intel Corporation Header File for Specific Absorption Rate
+ * Copyright (c) 2021, Intel Corporation.
+ */
+#ifndef INTEL_SAR_H
+#define INTEL_SAR_H
+
+#define DRVNAME "intc_sar"
+#define SYSFS_DATANAME "intc_data"
+#define SAR_DSM_UUID "82737E72-3A33-4C45-A9C7-57C0411A5F13"
+#define COMMAND_ID_DEV_MODE 1
+#define COMMAND_ID_CONFIG_TABLE 2
+#define COMMAND_TEST_SET 31
+#define MAX_REGULATORY 3
+#define SAR_EVENT 0x80
+#define MAX_DEV_MODES 50
+#define TOTAL_DATA 4
+
+/**
+ * Structure wwan_device_mode_info - device mode information
+ * Holds the data that needs to be passed to userspace.
+ * The data is updated from the BIOS sensor information.
+ * @device_mode: Specific mode of the device
+ * @bandtable_index: Index of RF band
+ * @antennatable_index: Index of antenna
+ * @sartable_index: Index of SAR
+ */
+struct wwan_device_mode_info {
+		int device_mode;
+		int bandtable_index;
+		int antennatable_index;
+		int sartable_index;
+};
+
+/**
+ * Structure wwan_device_mode_configuration - device configuration
+ * Holds the data that is configured and obtained on probe event.
+ * The data is updated from the BIOS sensor information.
+ * @version: Mode configuration version
+ * @total_dev_mode: Total number of device modes
+ * @device_mode_info: pointer to structure wwan_device_mode_info
+ */
+struct wwan_device_mode_configuration {
+		int version;
+		int total_dev_mode;
+		struct wwan_device_mode_info *device_mode_info;
+};
+
+/**
+ * Structure wwan_supported_info - userspace datastore
+ * Holds the data that is obtained from userspace
+ * The data is updated from the userspace and send value back in the
+ * structure format that is mentioned here.
+ * @reg_mode_needed: regulatory mode set by user for tests
+ * @bios_table_revision: Version of SAR table
+ * @num_supported_modes: Total supported modes based on reg_mode
+ */
+struct wwan_supported_info {
+		int reg_mode_needed;
+		int bios_table_revision;
+		int num_supported_modes;
+};
+
+/**
+ * Structure wwan_sar_context - context of SAR
+ * Holds the complete context as long as the driver is in existence
+ * The context holds instance of the data used for different cases.
+ * @guid: Group id
+ * @handle: store acpi handle
+ * @reg_value: regulatory value
+ * Regulatory 0: FCC, 1: CE, 2: ISED
+ * @sar_device: platform_device type
+ * @sar_kobject: kobject for sysfs
+ * @supported_data: wwan_supported_info struct
+ * @sar_data: wwan_device_mode_info struct
+ * @config_data: wwan_device_mode_configuration array struct
+ */
+struct wwan_sar_context {
+		guid_t guid;
+		acpi_handle handle;
+		int reg_value;
+		struct platform_device *sar_device;
+		struct kobject *sar_kobject;
+		struct wwan_supported_info supported_data;
+		struct wwan_device_mode_info sar_data;
+		struct wwan_device_mode_configuration config_data[MAX_REGULATORY];
+};
+#endif /* INTEL_SAR_H */
-- 
2.17.1

Re: [PATCH V3 1/1] platform/x86: Add BIOS Dynamic SAR driver for Intel M.2 Modem

[Hans de Goede]

Hi,

Thank you for the new version.

On 6/2/21 7:01 AM, Shravan S wrote:
> BIOS SAR (Specific Absorption Rate) driver for RF power regulation on Intel M.2 Modem.
> Limits the exposure of human body to RF frequencies.
> Uses ACPI to communicate to BIOS to retrieve SAR information data.
> Uses Sysfs to communicate this data to userspace via read and notify.
> Userspace will further use MBIM interface to enable data communication to modem.

Please limit the line length of the lines in your commit message to 75 chars.

I assume you are going to maintain this driver going forward? Please add an
entry to the MAINTAINERS file for the new driver.

> 
> Signed-off-by: Shravan S <s.shravan@intel.com>
> ---
> V3 :
> * Changes to the remove netlink and introduce sysfs to communicate to Userspace via notify
> * Handled review comments by changing ioctl calls to sysfs
> * "sar" name change for platform_device_id to "intc1092"
> * sar_init and sar_exit is modified as per review to minimal initialization
> * logging reduction and cleanup based on reviews.
> 
> ---
>  .../networking/device_drivers/wwan/index.rst  |   9 +-
>  .../device_drivers/wwan/intc_sar.rst          |  60 ++++
>  drivers/platform/x86/Kconfig                  |  12 +
>  drivers/platform/x86/Makefile                 |   1 +
>  drivers/platform/x86/intel-sar.c              | 326 ++++++++++++++++++
>  include/linux/platform_data/x86/intel-sar.h   |  89 +++++
>  6 files changed, 493 insertions(+), 4 deletions(-)
>  create mode 100644 Documentation/networking/device_drivers/wwan/intc_sar.rst
>  create mode 100644 drivers/platform/x86/intel-sar.c
>  create mode 100644 include/linux/platform_data/x86/intel-sar.h
> 
> diff --git a/Documentation/networking/device_drivers/wwan/index.rst b/Documentation/networking/device_drivers/wwan/index.rst
> index 1cb8c7371401..93dfd89f76e8 100644
> --- a/Documentation/networking/device_drivers/wwan/index.rst
> +++ b/Documentation/networking/device_drivers/wwan/index.rst
> @@ -1,14 +1,15 @@
> -.. SPDX-License-Identifier: GPL-2.0-only
> +.. SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
>  
> -WWAN Device Drivers
> -===================
> +Classic WAN Device Drivers
> +==========================

Why are you adding "Classic " here?

>  
>  Contents:
>  
>  .. toctree::
>     :maxdepth: 2
>  
> -   iosm

Why are you removing iosm here ?

> +   z8530book
> +   intc_sar

Why are you adding z8530book here ?

Please limit the changes to this file to just adding the intc_sar line,
any other changes should be done in a separate patch.

>  
>  .. only::  subproject and html
>  
> diff --git a/Documentation/networking/device_drivers/wwan/intc_sar.rst b/Documentation/networking/device_drivers/wwan/intc_sar.rst
> new file mode 100644
> index 000000000000..7319d6e593ed
> --- /dev/null
> +++ b/Documentation/networking/device_drivers/wwan/intc_sar.rst
> @@ -0,0 +1,60 @@
> +.. SPDX-License-Identifier: GPL-2.0-only
> +
> +.. Copyright (C) 2020-21 Intel Corporation
> +
> +.. _INTEL_SAR_driver_doc:
> +
> +===========================================
> +BIOS Dynamic SAR driver for Intel M.2 Modem
> +===========================================
> +SAR (Specific Absorption Rate) driver is a host driver implemented for Linux
> +or chrome platform to limit the exposure of human body to RF frequency by
> +informing the Intel M.2 modem to regulate the RF power based on SAR data
> +obtained from the sensors captured in the BIOS.
> +
> +Basic usage
> +===========
> +ACPI interface exposes this data from the BIOS to SAR driver. The front end
> +application in userspace ( eg: Modem Manager) will interact with SAR driver 
> +to obtain information like the device mode (Example: tablets, laptops, etx),
> +Antenna index, baseband index, SAR table index and use available communication
> +like MBIM interface to enable data communication to modem for power regulation.
> +
> +Applications to carry out below required actions for establishing connection
> +with driver for data communication with the SAR driver:
> +- open the sysfs file for communication
> +- read the data to get the information
> +- get notification from sysfs if data is changed
> +- write into sysfs to change regulatory mode.
> +
> +Management application development
> +==================================
> +The driver and userspace interfaces are described below.
> +
> +sysfs channel for communication to userspace
> +--------------------------------------------
> +
> +/sys/bus/platform/devices/INTC1092:00/intc_reg
> +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> +The driver exposes an sysfs entry in the kernel which is used for sending and
> +receiving regulatory information. The regulatory modes are depending on network.
> +FCC(0), CE(1), ISED(2)
> +
> +/sys/bus/platform/devices/INTC1092:00/intc_reg write()
> +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> +The regulatory modes should not exceed the allowed reguulatory worldwide.

Typo in reguulatory, also it is not clear to me what you are trying
to say here.

> +
> +/sys/bus/platform/devices/INTC1092:00/intc_reg read()
> +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> +The application can read the current regulatory mode that is set in the
> +driver.
> +
> +/sys/bus/platform/devices/INTC1092:00/intc_data
> +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> +The driver exposes an sysfs entry in the kernel which is used for receiving
> +information sent by BIOS.
> +
> +/sys/bus/platform/devices/INTC1092:00/intc_data read()
> +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> +The SAR index, Band index and Antenna index along with the device modes are
> +obtained from this sysfs.

This whole sysfs API description is pretty vague, also since the main goal
of this file is documenting the sysfs ABI it should live under
Documentation/ABI/testing/sysfs-driver-intc_sar

Then you also don't need to modify
Documentation/networking/device_drivers/wwan/index.rst

Having the docs for a drivers/platform/x86 driver live under
Documentation/networking/ is also weird, putting this in
Documentation/ABI/testing/sysfs-driver-intc_sar also resolves this.

Note these files have a different format, see:
Documentation/ABI/testing/sysfs-class-firmware-attributes
for example.


> diff --git a/drivers/platform/x86/Kconfig b/drivers/platform/x86/Kconfig
> index 7d385c3b2239..f3abf935a976 100644
> --- a/drivers/platform/x86/Kconfig
> +++ b/drivers/platform/x86/Kconfig
> @@ -1306,6 +1306,18 @@ config INTEL_TELEMETRY
>  	  directly via debugfs files. Various tools may use
>  	  this interface for SoC state monitoring.
>  
> +config INTEL_SAR
> +	tristate "Intel Specific Absorption Rate Driver"
> +	depends on ACPI
> +	help
> +	  This driver limit the exposure of human body to RF frequency by informing
> +	  the Intel M.2 modem to regulate the RF power based on SAR data obtained
> +	  from the sensors captured in the BIOS.

The driver itself does not limit the tx strength, it only provides information
which is used by other software to determine the max safe tx strength, please
update the description to reflect this.

Also please add some information when a user building their own kernels should
enable this.

Regards,

Hans


 ACPI interface exposes this data
> +	  from the BIOS to SAR driver. The front end application in userspace
> +	  will interact with SAR driver to obtain information like the device mode,
> +	  Antenna index, baseband index, SAR table index and use available communication
> +	  like MBIM interface to enable data communication to modem for RF power regulation.
> +
>  endif # X86_PLATFORM_DEVICES
>  
>  config PMC_ATOM
> diff --git a/drivers/platform/x86/Makefile b/drivers/platform/x86/Makefile
> index 7ee369aab10d..3610ab7a12df 100644
> --- a/drivers/platform/x86/Makefile
> +++ b/drivers/platform/x86/Makefile
> @@ -123,6 +123,7 @@ obj-$(CONFIG_INTEL_SMARTCONNECT)		+= intel-smartconnect.o
>  obj-$(CONFIG_INTEL_SPEED_SELECT_INTERFACE)	+= intel_speed_select_if/
>  obj-$(CONFIG_INTEL_TURBO_MAX_3)			+= intel_turbo_max_3.o
>  obj-$(CONFIG_INTEL_UNCORE_FREQ_CONTROL)		+= intel-uncore-frequency.o
> +obj-$(CONFIG_INTEL_SAR)				+= intel-sar.o
>  
>  # Intel PMIC / PMC / P-Unit devices
>  obj-$(CONFIG_INTEL_BXTWC_PMIC_TMU)	+= intel_bxtwc_tmu.o
> diff --git a/drivers/platform/x86/intel-sar.c b/drivers/platform/x86/intel-sar.c
> new file mode 100644
> index 000000000000..9906eb4d79a7
> --- /dev/null
> +++ b/drivers/platform/x86/intel-sar.c
> @@ -0,0 +1,326 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Intel Corporation - ACPI for Specific Absorption Rate
> + * Copyright (c) 2021, Intel Corporation.
> + */
> +
> +#include <asm/errno.h>
> +#include <linux/acpi.h>
> +#include <linux/kobject.h>
> +#include <linux/platform_data/x86/intel-sar.h>
> +#include <linux/platform_device.h>
> +#include <linux/sysfs.h>
> +
> +/**
> + * get_int_value - Retrieve Integer values from ACPI Object
> + * Value of the integer from the object of ACPI is obtained.
> + * @obj: acpi_object pointer which has the integer value
> + * @out: output pointer will get integer value
> + * returns 0 on success
> + */
> +static int get_int_value(union acpi_object *obj, int *out)
> +{
> +	if (obj && obj->type == ACPI_TYPE_INTEGER) {
> +		*out = (int)obj->integer.value;
> +		return 0;
> +	} else {
> +		return -EFAULT;
> +	}
> +}
> +
> +/**
> + * update_sar_data - sar data is updated based on reg_value
> + * sar_data is updated based on regulatory value
> + * context->reg_value will never exceed MAX_REGULATORY
> + * @context: context pointer used for data
> + */
> +static void update_sar_data(struct wwan_sar_context *context)
> +{
> +	struct wwan_device_mode_configuration *config =
> +	&context->config_data[context->reg_value];
> +
> +	if (config->device_mode_info &&
> +	    context->sar_data.device_mode <= config->total_dev_mode) {
> +		struct wwan_device_mode_info *dev_mode =
> +		&config->device_mode_info[context->sar_data.device_mode];
> +		context->sar_data.antennatable_index = dev_mode->antennatable_index;
> +		context->sar_data.bandtable_index = dev_mode->bandtable_index;
> +		context->sar_data.sartable_index = dev_mode->sartable_index;
> +	}
> +}
> +
> +/**
> + * parse_package - parse package for SAR
> + * @context: context pointer used for data
> + * @item : acpi_object ptr
> + * returns if success or error
> + */
> +static acpi_status parse_package(struct wwan_sar_context *context, union acpi_object *item)
> +{
> +	int value = 0, itr = 0, reg = 0;
> +	union acpi_object *num;
> +	struct wwan_device_mode_configuration *data;
> +
> +	num = &item->package.elements[0];
> +	if (get_int_value(num, &value) == 0) {
> +		if (value >= 0 && value < MAX_REGULATORY)
> +			reg = value;
> +		else
> +			return AE_ERROR;
> +	}
> +	data = &context->config_data[reg];
> +	if (data->total_dev_mode > MAX_DEV_MODES)
> +		return AE_ERROR;
> +	data->device_mode_info =
> +	kmalloc_array(data->total_dev_mode, sizeof(struct wwan_device_mode_info), GFP_KERNEL);
> +	if (!data->device_mode_info) {
> +		pr_err("Cannot allocate memory in kernel\n");
> +		return AE_ERROR;
> +	}
> +	for (itr = 0; itr < data->total_dev_mode; itr++) {
> +		if (itr + 1 == item->package.count)
> +			break;
> +		num = &item->package.elements[itr + 1];
> +		if (num->type != ACPI_TYPE_PACKAGE)
> +			continue;
> +		if (num->package.count < TOTAL_DATA)
> +			break;
> +		if (get_int_value(&num->package.elements[0], &value) == 0)
> +			data->device_mode_info[itr].device_mode = value;
> +		if (get_int_value(&num->package.elements[1], &value) == 0)
> +			data->device_mode_info[itr].bandtable_index = value;
> +		if (get_int_value(&num->package.elements[2], &value) == 0)
> +			data->device_mode_info[itr].antennatable_index = value;
> +		if (get_int_value(&num->package.elements[3], &value) == 0)
> +			data->device_mode_info[itr].sartable_index = value;
> +	}
> +	return AE_OK;
> +}
> +
> +/**
> + * sar_module_probe - Extraction of information from BIOS via DSM calls
> + * Retrieve all values related to device mode, SAR Table index,
> + * Antenna Table index, Band Table index
> + * @device: ACPI device for which to retrieve the data
> + * Returns AE_OK on success
> + */
> +static acpi_status sar_module_probe(struct platform_device *device)
> +{
> +	acpi_status status = AE_OK;
> +	union acpi_object *out;
> +	u32 rev = 0;
> +	int value = 0;
> +	struct wwan_sar_context *context = dev_get_drvdata(&device->dev);
> +
> +	pr_alert("%s Triggered\n", __func__);
> +	out = acpi_evaluate_dsm(context->handle, &context->guid, rev,
> +				COMMAND_ID_DEV_MODE, NULL);
> +	if (get_int_value(out, &value) == 0) {
> +		context->sar_data.device_mode = value;
> +	} else {
> +		pr_err("%s: Cmd:%d Failed\n", __func__, COMMAND_ID_DEV_MODE);
> +		ACPI_FREE(out);
> +		return AE_ERROR;
> +	}
> +	ACPI_FREE(out);
> +	dev_set_drvdata(&device->dev, context);
> +	sysfs_notify(context->sar_kobject, NULL, SYSFS_DATANAME);
> +	return status;
> +}
> +
> +static const struct acpi_device_id sar_device_ids[] = {
> +	{ "INTC1092", 0},
> +	{ "", 0},
> +};
> +
> +MODULE_DEVICE_TABLE(acpi, sar_device_ids);
> +
> +static const struct platform_device_id sar_device_table[] = {
> +	{"intc1092", 0},
> +	{},
> +};
> +
> +static ssize_t intc_data_show(struct device *dev, struct device_attribute *attr, char *buf)
> +{
> +	unsigned long ret = 0;
> +	struct wwan_sar_context *context = dev_get_drvdata(dev);
> +
> +	ret = sprintf(buf, "%d %d %d %d\n", context->sar_data.device_mode,
> +		      context->sar_data.bandtable_index,
> +		      context->sar_data.antennatable_index,
> +		      context->sar_data.sartable_index);
> +	return ret;
> +}
> +
> +static ssize_t intc_reg_show(struct device *dev, struct device_attribute *attr, char *buf)
> +{
> +	unsigned long ret = 0;
> +	struct wwan_sar_context *context = dev_get_drvdata(dev);
> +
> +	ret = sprintf(buf, "%d\n", context->reg_value);
> +	return ret;
> +}
> +
> +static ssize_t intc_reg_store(struct device *dev, struct device_attribute *attr,
> +			      const char *buf, size_t count)
> +{
> +	int value = 0, read = 0;
> +	struct wwan_sar_context *context = dev_get_drvdata(dev);
> +
> +	if (!count) {
> +		pr_err("%s count = %d", __func__, (int)count);
> +		return -EFAULT;
> +	}
> +	read = sscanf(buf, "%u", &value);
> +	if (read <= 0) {
> +		pr_alert("%s Not a integer", __func__);
> +		return -EFAULT;
> +	}
> +	if (value >= 0 && value < MAX_REGULATORY) {
> +		context->reg_value = value;
> +		update_sar_data(context);
> +		dev_set_drvdata(dev, context);
> +		sysfs_notify(context->sar_kobject, NULL, SYSFS_DATANAME);
> +	}
> +	return count;
> +}
> +
> +static DEVICE_ATTR_RO(intc_data);
> +static DEVICE_ATTR_RW(intc_reg);
> +
> +static struct attribute *intcsar_attrs[] = {
> +	&dev_attr_intc_data.attr,
> +	&dev_attr_intc_reg.attr,
> +	NULL
> +};
> +
> +static struct attribute_group intcsar_group = {
> +	.attrs = intcsar_attrs,
> +};
> +
> +static void sar_notify(acpi_handle handle, u32 event, void *data)
> +{
> +	struct platform_device *device = data;
> +
> +	if (event == SAR_EVENT) {
> +		if (sar_module_probe(device) != AE_OK)
> +			pr_err("sar_module_probe error");
> +	}
> +}
> +
> +static int sar_probe(struct platform_device *device)
> +{
> +	int result = 0;
> +	struct wwan_sar_context *context;
> +	union acpi_object *out, *item, req;
> +	acpi_status status = AE_OK;
> +	u32 rev = 0, reg = 0;
> +	int value = 0;
> +
> +	context = kmalloc(sizeof(*context), GFP_KERNEL);
> +	if (!context)
> +		return -ENOMEM;
> +	memset(context, 0, sizeof(struct wwan_sar_context));
> +	result = sysfs_create_group(&device->dev.kobj, &intcsar_group);
> +	if (result) {
> +		pr_err("sysfs creation failed\n");
> +		goto r_free;
> +	}
> +	context->sar_kobject = &device->dev.kobj;
> +	context->sar_device = device;
> +	dev_set_drvdata(&device->dev, context);
> +	if (guid_parse(SAR_DSM_UUID, &context->guid)) {
> +		pr_err("%s: UUID error\n", __func__);
> +		goto r_sys;
> +	}
> +	context->handle = ACPI_HANDLE(&device->dev);
> +	for (reg = 0; reg < MAX_REGULATORY; reg++) {
> +		req.type = ACPI_TYPE_INTEGER;
> +		req.integer.value = reg;
> +		out = acpi_evaluate_dsm(context->handle, &context->guid, rev,
> +					COMMAND_ID_CONFIG_TABLE, &req);
> +		if (!out) {
> +			pr_err("%s: Cmd:%d Failed\n", __func__, COMMAND_ID_CONFIG_TABLE);
> +			continue;
> +		}
> +		if (out->type == ACPI_TYPE_PACKAGE && out->package.count >= 3) {
> +			item = &out->package.elements[0];
> +			if (get_int_value(item, &value) == 0)
> +				context->config_data[reg].version = value;
> +			item = &out->package.elements[1];
> +			if (get_int_value(item, &value) == 0)
> +				context->config_data[reg].total_dev_mode = value;
> +			if (context->config_data[reg].total_dev_mode <= 0 &&
> +			    context->config_data[reg].total_dev_mode >
> +				MAX_DEV_MODES) {
> +				pr_err("total_dev_mode is not within range : %d\n",
> +				       context->config_data[reg].total_dev_mode);
> +				ACPI_FREE(out);
> +				continue;
> +			}
> +			item = &out->package.elements[2];
> +			if (item->type == ACPI_TYPE_PACKAGE && item->package.count > 0)
> +				status = parse_package(context, item);
> +			else
> +				status = AE_ERROR;
> +			if (status != AE_OK) {
> +				ACPI_FREE(out);
> +				continue;
> +			}
> +		}
> +		ACPI_FREE(out);
> +	}
> +	update_sar_data(context);
> +	if (sar_module_probe(device) != AE_OK) {
> +		pr_err("Failed sar_module_probe\n");
> +		goto r_sys;
> +	}
> +	if (acpi_install_notify_handler(ACPI_HANDLE(&device->dev), ACPI_DEVICE_NOTIFY,
> +					sar_notify, (void *)device) != AE_OK) {
> +		pr_err("Failed acpi_install_notify_handler\n");
> +		goto r_sys;
> +	}
> +	return 0;
> +
> +r_sys:
> +	sysfs_remove_group(&device->dev.kobj, &intcsar_group);
> +r_free:
> +	kfree(context);
> +	return -1;
> +}
> +
> +static int sar_remove(struct platform_device *device)
> +{
> +	struct wwan_sar_context *context = dev_get_drvdata(&device->dev);
> +	int reg = 0;
> +
> +	acpi_remove_notify_handler(ACPI_HANDLE(&device->dev),
> +				   ACPI_DEVICE_NOTIFY, sar_notify);
> +	sysfs_remove_group(&device->dev.kobj, &intcsar_group);
> +	for (reg = 0; reg < MAX_REGULATORY; reg++) {
> +		kfree(context->config_data[reg].device_mode_info);
> +		context->config_data[reg].device_mode_info = NULL;
> +	}
> +	kfree(context);
> +	return 0;
> +}
> +
> +MODULE_DEVICE_TABLE(platform, sar_device_table);
> +
> +static struct platform_driver sar_driver = {
> +	.probe = sar_probe,
> +	.remove = sar_remove,
> +	.driver = {
> +			.name = DRVNAME,
> +			.owner = THIS_MODULE,
> +			/* FOR ACPI HANDLING */
> +			.acpi_match_table = ACPI_PTR(sar_device_ids),
> +			},
> +	.id_table = sar_device_table,
> +};
> +
> +module_platform_driver(sar_driver);
> +
> +MODULE_LICENSE("GPL v2");
> +MODULE_DESCRIPTION("Platform device driver for INTEL MODEM BIOS SAR");
> +MODULE_AUTHOR("Shravan S <s.shravan@intel.com>");
> diff --git a/include/linux/platform_data/x86/intel-sar.h b/include/linux/platform_data/x86/intel-sar.h
> new file mode 100644
> index 000000000000..6e2ac93a3ebc
> --- /dev/null
> +++ b/include/linux/platform_data/x86/intel-sar.h
> @@ -0,0 +1,89 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Intel Corporation Header File for Specific Absorption Rate
> + * Copyright (c) 2021, Intel Corporation.
> + */
> +#ifndef INTEL_SAR_H
> +#define INTEL_SAR_H
> +
> +#define DRVNAME "intc_sar"
> +#define SYSFS_DATANAME "intc_data"
> +#define SAR_DSM_UUID "82737E72-3A33-4C45-A9C7-57C0411A5F13"
> +#define COMMAND_ID_DEV_MODE 1
> +#define COMMAND_ID_CONFIG_TABLE 2
> +#define COMMAND_TEST_SET 31
> +#define MAX_REGULATORY 3
> +#define SAR_EVENT 0x80
> +#define MAX_DEV_MODES 50
> +#define TOTAL_DATA 4
> +
> +/**
> + * Structure wwan_device_mode_info - device mode information
> + * Holds the data that needs to be passed to userspace.
> + * The data is updated from the BIOS sensor information.
> + * @device_mode: Specific mode of the device
> + * @bandtable_index: Index of RF band
> + * @antennatable_index: Index of antenna
> + * @sartable_index: Index of SAR
> + */
> +struct wwan_device_mode_info {
> +		int device_mode;
> +		int bandtable_index;
> +		int antennatable_index;
> +		int sartable_index;
> +};
> +
> +/**
> + * Structure wwan_device_mode_configuration - device configuration
> + * Holds the data that is configured and obtained on probe event.
> + * The data is updated from the BIOS sensor information.
> + * @version: Mode configuration version
> + * @total_dev_mode: Total number of device modes
> + * @device_mode_info: pointer to structure wwan_device_mode_info
> + */
> +struct wwan_device_mode_configuration {
> +		int version;
> +		int total_dev_mode;
> +		struct wwan_device_mode_info *device_mode_info;
> +};
> +
> +/**
> + * Structure wwan_supported_info - userspace datastore
> + * Holds the data that is obtained from userspace
> + * The data is updated from the userspace and send value back in the
> + * structure format that is mentioned here.
> + * @reg_mode_needed: regulatory mode set by user for tests
> + * @bios_table_revision: Version of SAR table
> + * @num_supported_modes: Total supported modes based on reg_mode
> + */
> +struct wwan_supported_info {
> +		int reg_mode_needed;
> +		int bios_table_revision;
> +		int num_supported_modes;
> +};
> +
> +/**
> + * Structure wwan_sar_context - context of SAR
> + * Holds the complete context as long as the driver is in existence
> + * The context holds instance of the data used for different cases.
> + * @guid: Group id
> + * @handle: store acpi handle
> + * @reg_value: regulatory value
> + * Regulatory 0: FCC, 1: CE, 2: ISED
> + * @sar_device: platform_device type
> + * @sar_kobject: kobject for sysfs
> + * @supported_data: wwan_supported_info struct
> + * @sar_data: wwan_device_mode_info struct
> + * @config_data: wwan_device_mode_configuration array struct
> + */
> +struct wwan_sar_context {
> +		guid_t guid;
> +		acpi_handle handle;
> +		int reg_value;
> +		struct platform_device *sar_device;
> +		struct kobject *sar_kobject;
> +		struct wwan_supported_info supported_data;
> +		struct wwan_device_mode_info sar_data;
> +		struct wwan_device_mode_configuration config_data[MAX_REGULATORY];
> +};
> +#endif /* INTEL_SAR_H */
> 

Re: [PATCH V3 1/1] platform/x86: Add BIOS Dynamic SAR driver for Intel M.2 Modem

[Hans de Goede]

Hi,

I accidentaly hit send before finishing my review, so it is continued here.

On 6/2/21 7:01 AM, Shravan S wrote:
> BIOS SAR (Specific Absorption Rate) driver for RF power regulation on Intel M.2 Modem.
> Limits the exposure of human body to RF frequencies.
> Uses ACPI to communicate to BIOS to retrieve SAR information data.
> Uses Sysfs to communicate this data to userspace via read and notify.
> Userspace will further use MBIM interface to enable data communication to modem.
> 
> Signed-off-by: Shravan S <s.shravan@intel.com>
> ---
> V3 :
> * Changes to the remove netlink and introduce sysfs to communicate to Userspace via notify
> * Handled review comments by changing ioctl calls to sysfs
> * "sar" name change for platform_device_id to "intc1092"
> * sar_init and sar_exit is modified as per review to minimal initialization
> * logging reduction and cleanup based on reviews.
> 
> ---
>  .../networking/device_drivers/wwan/index.rst  |   9 +-
>  .../device_drivers/wwan/intc_sar.rst          |  60 ++++
>  drivers/platform/x86/Kconfig                  |  12 +
>  drivers/platform/x86/Makefile                 |   1 +
>  drivers/platform/x86/intel-sar.c              | 326 ++++++++++++++++++
>  include/linux/platform_data/x86/intel-sar.h   |  89 +++++
>  6 files changed, 493 insertions(+), 4 deletions(-)
>  create mode 100644 Documentation/networking/device_drivers/wwan/intc_sar.rst
>  create mode 100644 drivers/platform/x86/intel-sar.c
>  create mode 100644 include/linux/platform_data/x86/intel-sar.h
> 
> diff --git a/Documentation/networking/device_drivers/wwan/index.rst b/Documentation/networking/device_drivers/wwan/index.rst
> index 1cb8c7371401..93dfd89f76e8 100644
> --- a/Documentation/networking/device_drivers/wwan/index.rst
> +++ b/Documentation/networking/device_drivers/wwan/index.rst
> @@ -1,14 +1,15 @@
> -.. SPDX-License-Identifier: GPL-2.0-only
> +.. SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
>  
> -WWAN Device Drivers
> -===================
> +Classic WAN Device Drivers
> +==========================
>  
>  Contents:
>  
>  .. toctree::
>     :maxdepth: 2
>  
> -   iosm
> +   z8530book
> +   intc_sar
>  
>  .. only::  subproject and html
>  
> diff --git a/Documentation/networking/device_drivers/wwan/intc_sar.rst b/Documentation/networking/device_drivers/wwan/intc_sar.rst
> new file mode 100644
> index 000000000000..7319d6e593ed
> --- /dev/null
> +++ b/Documentation/networking/device_drivers/wwan/intc_sar.rst
> @@ -0,0 +1,60 @@
> +.. SPDX-License-Identifier: GPL-2.0-only
> +
> +.. Copyright (C) 2020-21 Intel Corporation
> +
> +.. _INTEL_SAR_driver_doc:
> +
> +===========================================
> +BIOS Dynamic SAR driver for Intel M.2 Modem
> +===========================================
> +SAR (Specific Absorption Rate) driver is a host driver implemented for Linux
> +or chrome platform to limit the exposure of human body to RF frequency by
> +informing the Intel M.2 modem to regulate the RF power based on SAR data
> +obtained from the sensors captured in the BIOS.
> +
> +Basic usage
> +===========
> +ACPI interface exposes this data from the BIOS to SAR driver. The front end
> +application in userspace ( eg: Modem Manager) will interact with SAR driver 
> +to obtain information like the device mode (Example: tablets, laptops, etx),
> +Antenna index, baseband index, SAR table index and use available communication
> +like MBIM interface to enable data communication to modem for power regulation.
> +
> +Applications to carry out below required actions for establishing connection
> +with driver for data communication with the SAR driver:
> +- open the sysfs file for communication
> +- read the data to get the information
> +- get notification from sysfs if data is changed
> +- write into sysfs to change regulatory mode.
> +
> +Management application development
> +==================================
> +The driver and userspace interfaces are described below.
> +
> +sysfs channel for communication to userspace
> +--------------------------------------------
> +
> +/sys/bus/platform/devices/INTC1092:00/intc_reg
> +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> +The driver exposes an sysfs entry in the kernel which is used for sending and
> +receiving regulatory information. The regulatory modes are depending on network.
> +FCC(0), CE(1), ISED(2)
> +
> +/sys/bus/platform/devices/INTC1092:00/intc_reg write()
> +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> +The regulatory modes should not exceed the allowed reguulatory worldwide.
> +
> +/sys/bus/platform/devices/INTC1092:00/intc_reg read()
> +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> +The application can read the current regulatory mode that is set in the
> +driver.
> +
> +/sys/bus/platform/devices/INTC1092:00/intc_data
> +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> +The driver exposes an sysfs entry in the kernel which is used for receiving
> +information sent by BIOS.
> +
> +/sys/bus/platform/devices/INTC1092:00/intc_data read()
> +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> +The SAR index, Band index and Antenna index along with the device modes are
> +obtained from this sysfs.
> diff --git a/drivers/platform/x86/Kconfig b/drivers/platform/x86/Kconfig
> index 7d385c3b2239..f3abf935a976 100644
> --- a/drivers/platform/x86/Kconfig
> +++ b/drivers/platform/x86/Kconfig
> @@ -1306,6 +1306,18 @@ config INTEL_TELEMETRY
>  	  directly via debugfs files. Various tools may use
>  	  this interface for SoC state monitoring.
>  
> +config INTEL_SAR
> +	tristate "Intel Specific Absorption Rate Driver"
> +	depends on ACPI
> +	help
> +	  This driver limit the exposure of human body to RF frequency by informing
> +	  the Intel M.2 modem to regulate the RF power based on SAR data obtained
> +	  from the sensors captured in the BIOS. ACPI interface exposes this data
> +	  from the BIOS to SAR driver. The front end application in userspace
> +	  will interact with SAR driver to obtain information like the device mode,
> +	  Antenna index, baseband index, SAR table index and use available communication
> +	  like MBIM interface to enable data communication to modem for RF power regulation.
> +
>  endif # X86_PLATFORM_DEVICES
>  
>  config PMC_ATOM
> diff --git a/drivers/platform/x86/Makefile b/drivers/platform/x86/Makefile
> index 7ee369aab10d..3610ab7a12df 100644
> --- a/drivers/platform/x86/Makefile
> +++ b/drivers/platform/x86/Makefile
> @@ -123,6 +123,7 @@ obj-$(CONFIG_INTEL_SMARTCONNECT)		+= intel-smartconnect.o
>  obj-$(CONFIG_INTEL_SPEED_SELECT_INTERFACE)	+= intel_speed_select_if/
>  obj-$(CONFIG_INTEL_TURBO_MAX_3)			+= intel_turbo_max_3.o
>  obj-$(CONFIG_INTEL_UNCORE_FREQ_CONTROL)		+= intel-uncore-frequency.o
> +obj-$(CONFIG_INTEL_SAR)				+= intel-sar.o
>  
>  # Intel PMIC / PMC / P-Unit devices
>  obj-$(CONFIG_INTEL_BXTWC_PMIC_TMU)	+= intel_bxtwc_tmu.o
> diff --git a/drivers/platform/x86/intel-sar.c b/drivers/platform/x86/intel-sar.c
> new file mode 100644
> index 000000000000..9906eb4d79a7
> --- /dev/null
> +++ b/drivers/platform/x86/intel-sar.c
> @@ -0,0 +1,326 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Intel Corporation - ACPI for Specific Absorption Rate
> + * Copyright (c) 2021, Intel Corporation.
> + */
> +
> +#include <asm/errno.h>
> +#include <linux/acpi.h>
> +#include <linux/kobject.h>
> +#include <linux/platform_data/x86/intel-sar.h>
> +#include <linux/platform_device.h>
> +#include <linux/sysfs.h>
> +
> +/**
> + * get_int_value - Retrieve Integer values from ACPI Object
> + * Value of the integer from the object of ACPI is obtained.
> + * @obj: acpi_object pointer which has the integer value
> + * @out: output pointer will get integer value
> + * returns 0 on success
> + */
> +static int get_int_value(union acpi_object *obj, int *out)
> +{
> +	if (obj && obj->type == ACPI_TYPE_INTEGER) {
> +		*out = (int)obj->integer.value;
> +		return 0;
> +	} else {
> +		return -EFAULT;

EFAULT must only be used when a userspace call passes an
invalid address to the kernel. All other uses of EFAULT are
wrong. Please use a different error here. Typically -EIO is
used when parsing firmware provided data and the contents
is not what we expect.

> +	}
> +}
> +
> +/**
> + * update_sar_data - sar data is updated based on reg_value
> + * sar_data is updated based on regulatory value
> + * context->reg_value will never exceed MAX_REGULATORY
> + * @context: context pointer used for data
> + */
> +static void update_sar_data(struct wwan_sar_context *context)
> +{
> +	struct wwan_device_mode_configuration *config =
> +	&context->config_data[context->reg_value];

Weird indentation please indent the value being assinged with a tab.

> +
> +	if (config->device_mode_info &&
> +	    context->sar_data.device_mode <= config->total_dev_mode) {

device_mode_info is an array with total_dev_mode entries this means
that device_mode == config->total_dev_mode will cause data to be
read beyond the end of the array, so the check should use "<"
instead of "<=".

> +		struct wwan_device_mode_info *dev_mode =
> +		&config->device_mode_info[context->sar_data.device_mode];

Weird indentation please indent the value being assinged with a tab and
always put a newline between the variable declerations and the regular statements
following them.

> +		context->sar_data.antennatable_index = dev_mode->antennatable_index;
> +		context->sar_data.bandtable_index = dev_mode->bandtable_index;
> +		context->sar_data.sartable_index = dev_mode->sartable_index;
> +	}
> +}
> +
> +/**
> + * parse_package - parse package for SAR
> + * @context: context pointer used for data
> + * @item : acpi_object ptr
> + * returns if success or error
> + */
> +static acpi_status parse_package(struct wwan_sar_context *context, union acpi_object *item)
> +{
> +	int value = 0, itr = 0, reg = 0;
> +	union acpi_object *num;
> +	struct wwan_device_mode_configuration *data;
> +
> +	num = &item->package.elements[0];
> +	if (get_int_value(num, &value) == 0) {
> +		if (value >= 0 && value < MAX_REGULATORY)
> +			reg = value;
> +		else
> +			return AE_ERROR;
> +	}

There is no error handling here for if get_int_value() fails, is that intentional?

> +	data = &context->config_data[reg];
> +	if (data->total_dev_mode > MAX_DEV_MODES)
> +		return AE_ERROR;
> +	data->device_mode_info =
> +	kmalloc_array(data->total_dev_mode, sizeof(struct wwan_device_mode_info), GFP_KERNEL);
> +	if (!data->device_mode_info) {
> +		pr_err("Cannot allocate memory in kernel\n");
> +		return AE_ERROR;
> +	}
> +	for (itr = 0; itr < data->total_dev_mode; itr++) {
> +		if (itr + 1 == item->package.count)
> +			break;
> +		num = &item->package.elements[itr + 1];
> +		if (num->type != ACPI_TYPE_PACKAGE)
> +			continue;

Why is this a continue;

> +		if (num->package.count < TOTAL_DATA)
> +			break;

And this a break ?

And shouldn't an error be logged in either of these cases ?

> +		if (get_int_value(&num->package.elements[0], &value) == 0)
> +			data->device_mode_info[itr].device_mode = value;
> +		if (get_int_value(&num->package.elements[1], &value) == 0)
> +			data->device_mode_info[itr].bandtable_index = value;
> +		if (get_int_value(&num->package.elements[2], &value) == 0)
> +			data->device_mode_info[itr].antennatable_index = value;
> +		if (get_int_value(&num->package.elements[3], &value) == 0)
> +			data->device_mode_info[itr].sartable_index = value;

Missing error handling for get_int_value failing (4 times).

> +	}
> +	return AE_OK;
> +}
> +
> +/**
> + * sar_module_probe - Extraction of information from BIOS via DSM calls
> + * Retrieve all values related to device mode, SAR Table index,
> + * Antenna Table index, Band Table index
> + * @device: ACPI device for which to retrieve the data
> + * Returns AE_OK on success
> + */

This comment no longer matches what this function actually does.

> +static acpi_status sar_module_probe(struct platform_device *device)

And the function name no longer makes sense too.

> +{
> +	acpi_status status = AE_OK;
> +	union acpi_object *out;
> +	u32 rev = 0;
> +	int value = 0;
> +	struct wwan_sar_context *context = dev_get_drvdata(&device->dev);
> +
> +	pr_alert("%s Triggered\n", __func__);

Please drop this debug statement.

Also you must never use pr_alert. The ALERT log level has higher
prio then the CRIT level which has higher priority then the standard
ERROR level. IOW you are using a log level here which is reserved
for things like the computer pretty much literary being on fire.


> +	out = acpi_evaluate_dsm(context->handle, &context->guid, rev,
> +				COMMAND_ID_DEV_MODE, NULL);
> +	if (get_int_value(out, &value) == 0) {
> +		context->sar_data.device_mode = value;
> +	} else {
> +		pr_err("%s: Cmd:%d Failed\n", __func__, COMMAND_ID_DEV_MODE);
> +		ACPI_FREE(out);
> +		return AE_ERROR;
> +	}
> +	ACPI_FREE(out);

Please refactor this so that there is only one ACPI_FREE(out) call.

> +	dev_set_drvdata(&device->dev, context);

This setting of drvdata here is bogus, you just retrieved it above,
please drop this line.

> +	sysfs_notify(context->sar_kobject, NULL, SYSFS_DATANAME);
> +	return status;

You never change status, please drop status and just call:

	return AE_OK;

here.

> +}
> +
> +static const struct acpi_device_id sar_device_ids[] = {
> +	{ "INTC1092", 0},
> +	{ "", 0},
> +};
> +
> +MODULE_DEVICE_TABLE(acpi, sar_device_ids);
> +
> +static const struct platform_device_id sar_device_table[] = {
> +	{"intc1092", 0},
> +	{},
> +};

This second device-id table is not nesessary, please drop it.

> +
> +static ssize_t intc_data_show(struct device *dev, struct device_attribute *attr, char *buf)
> +{
> +	unsigned long ret = 0;
> +	struct wwan_sar_context *context = dev_get_drvdata(dev);
> +
> +	ret = sprintf(buf, "%d %d %d %d\n", context->sar_data.device_mode,
> +		      context->sar_data.bandtable_index,
> +		      context->sar_data.antennatable_index,
> +		      context->sar_data.sartable_index);
> +	return ret;
> +}

Use sysfs_emit here please, also make ret a ssize_t, or directly return the
sysfs_emit return value.

> +
> +static ssize_t intc_reg_show(struct device *dev, struct device_attribute *attr, char *buf)
> +{
> +	unsigned long ret = 0;
> +	struct wwan_sar_context *context = dev_get_drvdata(dev);
> +
> +	ret = sprintf(buf, "%d\n", context->reg_value);
> +	return ret;

Same.

> +}
> +
> +static ssize_t intc_reg_store(struct device *dev, struct device_attribute *attr,
> +			      const char *buf, size_t count)
> +{
> +	int value = 0, read = 0;
> +	struct wwan_sar_context *context = dev_get_drvdata(dev);
> +
> +	if (!count) {
> +		pr_err("%s count = %d", __func__, (int)count);
> +		return -EFAULT;
> +	}
> +	read = sscanf(buf, "%u", &value);
> +	if (read <= 0) {
> +		pr_alert("%s Not a integer", __func__);
> +		return -EFAULT;
> +	}

Use kstrtoul here please
 
> +	if (value >= 0 && value < MAX_REGULATORY) {


You should return  -EINVAL when value is outside of this
range. Using kstrotul makes sure that value is not negative, so then
you just have to do:

	if (value >= MAX_REGULATORY)
		return -EINVAL;



> +		context->reg_value = value;
> +		update_sar_data(context);
> +		dev_set_drvdata(dev, context);
> +		sysfs_notify(context->sar_kobject, NULL, SYSFS_DATANAME);

And then do these unconditional (ident them one tab level to the left).

> +	}
> +	return count;
> +}
> +
> +static DEVICE_ATTR_RO(intc_data);
> +static DEVICE_ATTR_RW(intc_reg);
> +
> +static struct attribute *intcsar_attrs[] = {
> +	&dev_attr_intc_data.attr,
> +	&dev_attr_intc_reg.attr,
> +	NULL
> +};
> +
> +static struct attribute_group intcsar_group = {
> +	.attrs = intcsar_attrs,
> +};
> +
> +static void sar_notify(acpi_handle handle, u32 event, void *data)
> +{
> +	struct platform_device *device = data;
> +
> +	if (event == SAR_EVENT) {
> +		if (sar_module_probe(device) != AE_OK)
> +			pr_err("sar_module_probe error");
> +	}> +}
> +
> +static int sar_probe(struct platform_device *device)
> +{
> +	int result = 0;
> +	struct wwan_sar_context *context;
> +	union acpi_object *out, *item, req;
> +	acpi_status status = AE_OK;
> +	u32 rev = 0, reg = 0;
> +	int value = 0;
> +
> +	context = kmalloc(sizeof(*context), GFP_KERNEL);
> +	if (!context)
> +		return -ENOMEM;
> +	memset(context, 0, sizeof(struct wwan_sar_context));
> +	result = sysfs_create_group(&device->dev.kobj, &intcsar_group);
> +	if (result) {
> +		pr_err("sysfs creation failed\n");
> +		goto r_free;
> +	}

Your sysfs files may get accessed as soon as you've made this call
abd you've not fully initialized context yet, so the sysfs_create_group
should be done at the end of probe(), just before calling
acpi_install_notify_handler()

> +	context->sar_kobject = &device->dev.kobj;
> +	context->sar_device = device;
> +	dev_set_drvdata(&device->dev, context);
> +	if (guid_parse(SAR_DSM_UUID, &context->guid)) {
> +		pr_err("%s: UUID error\n", __func__);
> +		goto r_sys;
> +	}
> +	context->handle = ACPI_HANDLE(&device->dev);
> +	for (reg = 0; reg < MAX_REGULATORY; reg++) {
> +		req.type = ACPI_TYPE_INTEGER;
> +		req.integer.value = reg;
> +		out = acpi_evaluate_dsm(context->handle, &context->guid, rev,
> +					COMMAND_ID_CONFIG_TABLE, &req);
> +		if (!out) {
> +			pr_err("%s: Cmd:%d Failed\n", __func__, COMMAND_ID_CONFIG_TABLE);
> +			continue;
> +		}
> +		if (out->type == ACPI_TYPE_PACKAGE && out->package.count >= 3) {
> +			item = &out->package.elements[0];
> +			if (get_int_value(item, &value) == 0)
> +				context->config_data[reg].version = value;

Error handling for get_int_value failing ?

> +			item = &out->package.elements[1];
> +			if (get_int_value(item, &value) == 0)
> +				context->config_data[reg].total_dev_mode = value;

Error handling for get_int_value failing ?

> +			if (context->config_data[reg].total_dev_mode <= 0 &&
> +			    context->config_data[reg].total_dev_mode >
> +				MAX_DEV_MODES) {

Instead of && you should use || in this check.

> +				pr_err("total_dev_mode is not within range : %d\n",
> +				       context->config_data[reg].total_dev_mode);
> +				ACPI_FREE(out);
> +				continue;
> +			}
> +			item = &out->package.elements[2];
> +			if (item->type == ACPI_TYPE_PACKAGE && item->package.count > 0)
> +				status = parse_package(context, item);

parse_package checks context->config_data[reg].total_dev_mode, where it reads reg from
the passed in item. What if this is a different reg then the one we are parsing?
Then context->config_data[reg].total_dev_mode will not be initialized yet. So I guess
that the reg read by parse_package() should always be the same as the reg value which we
passed to the DSM ?  If that is true then reg should be passed to parse_package here;
and parse_package should check that it matches.

Also you basically expect here that:

out->package.elements[0].type == ACPI_TYPE_INTEGER &&
out->package.elements[1].type == ACPI_TYPE_INTEGER &&
out->package.elements[2].type == ACPI_TYPE_PACKAGE

I believe the code would be simpler if you add this as extra conditions to the

		if (out->type == ACPI_TYPE_PACKAGE && out->package.count >= 3)

check.


> +			else
> +				status = AE_ERROR;
> +			if (status != AE_OK) {
> +				ACPI_FREE(out);
> +				continue;
> +			}
> +		}
> +		ACPI_FREE(out);
> +	}
> +	update_sar_data(context);
> +	if (sar_module_probe(device) != AE_OK) {
> +		pr_err("Failed sar_module_probe\n");
> +		goto r_sys;
> +	}
> +	if (acpi_install_notify_handler(ACPI_HANDLE(&device->dev), ACPI_DEVICE_NOTIFY,
> +					sar_notify, (void *)device) != AE_OK) {
> +		pr_err("Failed acpi_install_notify_handler\n");
> +		goto r_sys;
> +	}
> +	return 0;
> +
> +r_sys:
> +	sysfs_remove_group(&device->dev.kobj, &intcsar_group);
> +r_free:
> +	kfree(context);
> +	return -1;
> +}
> +
> +static int sar_remove(struct platform_device *device)
> +{
> +	struct wwan_sar_context *context = dev_get_drvdata(&device->dev);
> +	int reg = 0;
> +
> +	acpi_remove_notify_handler(ACPI_HANDLE(&device->dev),
> +				   ACPI_DEVICE_NOTIFY, sar_notify);
> +	sysfs_remove_group(&device->dev.kobj, &intcsar_group);
> +	for (reg = 0; reg < MAX_REGULATORY; reg++) {
> +		kfree(context->config_data[reg].device_mode_info);
> +		context->config_data[reg].device_mode_info = NULL;
> +	}
> +	kfree(context);
> +	return 0;
> +}
> +
> +MODULE_DEVICE_TABLE(platform, sar_device_table);
> +
> +static struct platform_driver sar_driver = {
> +	.probe = sar_probe,
> +	.remove = sar_remove,
> +	.driver = {
> +			.name = DRVNAME,
> +			.owner = THIS_MODULE,
> +			/* FOR ACPI HANDLING */
> +			.acpi_match_table = ACPI_PTR(sar_device_ids),
> +			},
> +	.id_table = sar_device_table,
> +};
> +
> +module_platform_driver(sar_driver);
> +
> +MODULE_LICENSE("GPL v2");
> +MODULE_DESCRIPTION("Platform device driver for INTEL MODEM BIOS SAR");
> +MODULE_AUTHOR("Shravan S <s.shravan@intel.com>");
> diff --git a/include/linux/platform_data/x86/intel-sar.h b/include/linux/platform_data/x86/intel-sar.h
> new file mode 100644
> index 000000000000..6e2ac93a3ebc
> --- /dev/null
> +++ b/include/linux/platform_data/x86/intel-sar.h
> @@ -0,0 +1,89 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Intel Corporation Header File for Specific Absorption Rate
> + * Copyright (c) 2021, Intel Corporation.
> + */
> +#ifndef INTEL_SAR_H
> +#define INTEL_SAR_H
> +
> +#define DRVNAME "intc_sar"
> +#define SYSFS_DATANAME "intc_data"
> +#define SAR_DSM_UUID "82737E72-3A33-4C45-A9C7-57C0411A5F13"
> +#define COMMAND_ID_DEV_MODE 1
> +#define COMMAND_ID_CONFIG_TABLE 2
> +#define COMMAND_TEST_SET 31
> +#define MAX_REGULATORY 3
> +#define SAR_EVENT 0x80
> +#define MAX_DEV_MODES 50
> +#define TOTAL_DATA 4
> +
> +/**
> + * Structure wwan_device_mode_info - device mode information
> + * Holds the data that needs to be passed to userspace.
> + * The data is updated from the BIOS sensor information.
> + * @device_mode: Specific mode of the device
> + * @bandtable_index: Index of RF band
> + * @antennatable_index: Index of antenna
> + * @sartable_index: Index of SAR
> + */
> +struct wwan_device_mode_info {
> +		int device_mode;
> +		int bandtable_index;
> +		int antennatable_index;
> +		int sartable_index;
> +};
> +
> +/**
> + * Structure wwan_device_mode_configuration - device configuration
> + * Holds the data that is configured and obtained on probe event.
> + * The data is updated from the BIOS sensor information.
> + * @version: Mode configuration version
> + * @total_dev_mode: Total number of device modes
> + * @device_mode_info: pointer to structure wwan_device_mode_info
> + */
> +struct wwan_device_mode_configuration {
> +		int version;
> +		int total_dev_mode;
> +		struct wwan_device_mode_info *device_mode_info;
> +};
> +
> +/**
> + * Structure wwan_supported_info - userspace datastore
> + * Holds the data that is obtained from userspace
> + * The data is updated from the userspace and send value back in the
> + * structure format that is mentioned here.
> + * @reg_mode_needed: regulatory mode set by user for tests
> + * @bios_table_revision: Version of SAR table
> + * @num_supported_modes: Total supported modes based on reg_mode
> + */
> +struct wwan_supported_info {
> +		int reg_mode_needed;
> +		int bios_table_revision;
> +		int num_supported_modes;
> +};
> +
> +/**
> + * Structure wwan_sar_context - context of SAR
> + * Holds the complete context as long as the driver is in existence
> + * The context holds instance of the data used for different cases.
> + * @guid: Group id
> + * @handle: store acpi handle
> + * @reg_value: regulatory value
> + * Regulatory 0: FCC, 1: CE, 2: ISED
> + * @sar_device: platform_device type
> + * @sar_kobject: kobject for sysfs
> + * @supported_data: wwan_supported_info struct
> + * @sar_data: wwan_device_mode_info struct
> + * @config_data: wwan_device_mode_configuration array struct
> + */
> +struct wwan_sar_context {
> +		guid_t guid;
> +		acpi_handle handle;
> +		int reg_value;
> +		struct platform_device *sar_device;
> +		struct kobject *sar_kobject;
> +		struct wwan_supported_info supported_data;
> +		struct wwan_device_mode_info sar_data;
> +		struct wwan_device_mode_configuration config_data[MAX_REGULATORY];
> +};
> +#endif /* INTEL_SAR_H */
> 


Regards,

Hans

Re: [PATCH V3 1/1] platform/x86: Add BIOS Dynamic SAR driver for Intel M.2 Modem

[Hans de Goede]

Hi Enrico,

On 2/17/23 21:27, Enrico Weigelt, metux IT consult wrote:
> On 02.08.21 10:59, Hans de Goede wrote:
> 
> <snip>
> 
>> The driver itself does not limit the tx strength, it only provides information
>> which is used by other software to determine the max safe tx strength, please
>> update the description to reflect this.
> 
> Also missing specification of the actual meaning of this data, and how
> to calculate max safe tx from that.
> 
> I hightly doubt we want proprietary / largely undocumented userland
> abi's in the kernel. The general rule for userland abi is that once
> introduced, shouldn't get any breaking changes, and should be applicable
> to all devices of the same class (independent from hw vendor/model)

This driver has long since been merged and AFAIK is being used
in production now, so this ship has long sailed since.

One remark which I do have here is that this implementation is
actually one of the least bad implementation of the whole SAR
stuff where WWAN modems dynamically adjust there tx power based
on if part of a humanbody is near the antenna or not.

This is all shrouded in secrecy and related to certification
processes in several countries. The way this specific driver /
interface works is that we simply have:

1) Kernel reads human-presence sensor info through standardized
ACPI interface (contents is unknown, but the interface for getting
the blob with readings is standard)

2. ModemManager reads human-presence sensor info from kernel
and sends this to the modem as part of the normal command stream
between ModemManager and the modem. ModemManager needs to be
in the loop here since it owns the interface to the modem.

This is much better then what some other WWAN modem vendors
have been trying to push where the process involves not only
mystery firmware APIs, but also a closed-source userspace process
to manage the dynamic SAR bits. So Intel's implementation where
all we need to do is to proxy between the BIOS/EC firmware and
the modem (because the EC cannot talk directly to the modem)
is actually pretty decent (compared to the other stuff).

Regards,

Hans