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misc: amd-apml: Add common device registration framework
Add centralized device registration system for AMD APML devices. Provides global device list where SBRMI and SBTSI drivers can register themselves, enabling the Alert_L driver to discover and safely process alerts from registered devices. Reviewed-by: Naveen Krishna Chatradhi <naveenkrishna.chatradhi@amd.com> Signed-off-by: sathya priya kumar <SathyaPriya.K@amd.com> Signed-off-by: Akshay Gupta <akshay.gupta@amd.com>
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‎drivers/misc/amd-apml/Kconfig‎

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# AMD APML BMC interface drivers
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#
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config APML_COMMON
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tristate "AMD APML common device registration framework"
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default n
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help
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Enable support for the AMD APML (Advanced Platform Management Link)
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common device registration framework. This module provides a centralized
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registry where APML devices (SBRMI and SBTSI) can register themselves
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for discovery by other APML subsystems.
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This framework enables the Alert_L driver to safely discover and access
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registered APML devices for alert processing across multiple sockets.
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config APML_SBRMI
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tristate "Emulated SB-RMI interface driver over i3c bus"
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depends on I3C && !SENSORS_SBRMI

‎drivers/misc/amd-apml/Makefile‎

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# AMD APML BMC interface drivers
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#
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obj-$(CONFIG_APML_COMMON) += apml_common.o
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obj-$(CONFIG_APML_SBRMI) += sbrmi.o sbrmi-common.o
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obj-$(CONFIG_APML_SBTSI) += apml_sbtsi.o
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obj-$(CONFIG_APML_ALERTL) += apml_alertl.o

‎drivers/misc/amd-apml/apml_common.c‎

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// SPDX-License-Identifier: GPL-2.0-or-later
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/*
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* apml-common.c - Common registration system for APML devices
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*
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* Copyright (C) 2025 Advanced Micro Devices, Inc.
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*/
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#include <linux/module.h>
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#include <linux/slab.h>
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#include <linux/i2c.h>
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#include <linux/i3c/device.h>
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#include <linux/i3c/master.h>
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#include <linux/mutex.h>
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#include <linux/list.h>
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#include <linux/kref.h>
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#include "apml_common.h"
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/* Global list of registered APML devices */
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LIST_HEAD(apml_devices);
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EXPORT_SYMBOL_GPL(apml_devices);
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/* Mutex to protect apml_devices list operations and device node access */
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DEFINE_MUTEX(apml_devices_lock);
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EXPORT_SYMBOL_GPL(apml_devices_lock);
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/* Release function for device node reference counting */
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static void apml_device_node_release(struct kref *ref)
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{
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struct apml_device_node *node = container_of(ref, struct apml_device_node, ref);
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kfree(node);
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}
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/* Get a reference to a device node - increases reference count */
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struct apml_device_node *apml_get_device_node(struct apml_device_node *node)
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{
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if (node && kref_get_unless_zero(&node->ref))
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return node;
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return NULL;
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}
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EXPORT_SYMBOL_GPL(apml_get_device_node);
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/* Put a reference to a device node - decreases reference count */
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void apml_put_device_node(struct apml_device_node *node)
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{
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if (node)
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kref_put(&node->ref, apml_device_node_release);
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}
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EXPORT_SYMBOL_GPL(apml_put_device_node);
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static void apml_add_device_node(struct apml_device_node *node)
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{
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mutex_lock(&apml_devices_lock);
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list_add_tail(&node->list, &apml_devices);
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mutex_unlock(&apml_devices_lock);
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}
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/* Device registration function */
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int apml_register_device(void *device, enum apml_device_type dev_type)
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{
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struct apml_device_node *node;
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struct apml_sbrmi_device *rmi_dev;
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struct apml_sbtsi_device *tsi_dev;
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if (!device) {
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pr_info("APML: Cannot register NULL device\n");
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return -EINVAL;
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}
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node = kzalloc(sizeof(*node), GFP_KERNEL);
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if (!node)
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return -ENOMEM;
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node->dev_type = dev_type;
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kref_init(&node->ref); /* Initialize reference count to 1 */
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switch (node->dev_type) {
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case APML_RMI_DEVICE:
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rmi_dev = (struct apml_sbrmi_device *)device;
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if (!rmi_dev->i3cdev && !rmi_dev->client) {
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pr_err("APML: Invalid RMI device - no I2C or I3C device\n");
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kfree(node);
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return -EINVAL;
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}
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node->rmi_dev = rmi_dev;
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pr_info("APML: Registered SBRMI device at address 0x%x\n",
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rmi_dev->i3cdev ? rmi_dev->dev_static_addr : rmi_dev->client->addr);
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break;
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case APML_TSI_DEVICE:
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tsi_dev = (struct apml_sbtsi_device *)device;
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if (!tsi_dev->i3cdev && !tsi_dev->client) {
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pr_info("APML: Invalid TSI device - no I2C or I3C device\n");
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kfree(node);
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return -EINVAL;
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}
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node->tsi_dev = tsi_dev;
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pr_info("APML: Registered SBTSI device at address 0x%x\n",
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tsi_dev->i3cdev ? tsi_dev->dev_static_addr : tsi_dev->client->addr);
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break;
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default:
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kfree(node);
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return -EINVAL;
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}
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apml_add_device_node(node);
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return 0;
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}
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/* Register an SBRMI device */
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int apml_register_sbrmi_device(struct apml_sbrmi_device *rmi_dev)
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{
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return apml_register_device(rmi_dev, APML_RMI_DEVICE);
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}
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EXPORT_SYMBOL_GPL(apml_register_sbrmi_device);
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/* Register an SBTSI device*/
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int apml_register_sbtsi_device(struct apml_sbtsi_device *tsi_dev)
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{
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return apml_register_device(tsi_dev, APML_TSI_DEVICE);
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}
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EXPORT_SYMBOL_GPL(apml_register_sbtsi_device);
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/* Device unregistration function*/
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void apml_unregister_device(void *device, enum apml_device_type dev_type)
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{
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struct apml_device_node *node, *tmp, *found_node = NULL;
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bool found = false;
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if (!device)
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return;
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/* Find and mark device as invalid and removing */
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mutex_lock(&apml_devices_lock);
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list_for_each_entry(node, &apml_devices, list) {
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if (node->dev_type != dev_type)
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continue;
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switch (dev_type) {
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case APML_RMI_DEVICE:
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if (node->rmi_dev == (struct apml_sbrmi_device *)device)
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found = true;
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break;
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case APML_TSI_DEVICE:
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if (node->tsi_dev == (struct apml_sbtsi_device *)device)
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found = true;
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break;
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}
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if (found) {
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/* Get a reference to keep node alive during removal */
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found_node = apml_get_device_node(node);
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break;
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}
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}
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mutex_unlock(&apml_devices_lock);
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if (!found_node)
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return;
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/* Remove from list and release reference */
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mutex_lock(&apml_devices_lock);
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list_for_each_entry_safe(node, tmp, &apml_devices, list) {
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if (node == found_node) {
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list_del(&node->list);
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break;
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}
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}
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mutex_unlock(&apml_devices_lock);
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/* Release our reference - this may free the node if no other references exist */
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apml_put_device_node(found_node);
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}
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/* Unregister an SBRMI device */
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void apml_unregister_sbrmi_device(struct apml_sbrmi_device *rmi_dev)
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{
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apml_unregister_device(rmi_dev, APML_RMI_DEVICE);
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}
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EXPORT_SYMBOL_GPL(apml_unregister_sbrmi_device);
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/* Unregister an SBTSI device */
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void apml_unregister_sbtsi_device(struct apml_sbtsi_device *tsi_dev)
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{
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apml_unregister_device(tsi_dev, APML_TSI_DEVICE);
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}
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EXPORT_SYMBOL_GPL(apml_unregister_sbtsi_device);
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MODULE_AUTHOR("Akshay Gupta <akshay.gupta@amd.com>");
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MODULE_AUTHOR("sathya priya kumar <SathyaPriya.K@amd.com>");
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MODULE_AUTHOR("Naveenkrishna Chatradhi <naveenkrishna.chatradhi@amd.com>");
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MODULE_DESCRIPTION("AMD APML Common Device Registration");
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MODULE_LICENSE("GPL");

‎drivers/misc/amd-apml/apml_common.h‎

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/* SPDX-License-Identifier: GPL-2.0-or-later */
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/*
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* Copyright (C) 2025 Advanced Micro Devices, Inc.
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*/
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#ifndef _AMD_APML_COMMON_H_
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#define _AMD_APML_COMMON_H_
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#include <linux/list.h>
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#include <linux/kref.h>
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#include "sbrmi-common.h"
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#include "sbtsi-common.h"
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extern struct list_head apml_devices;
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extern struct mutex apml_devices_lock;
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enum apml_device_type {
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APML_RMI_DEVICE,
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APML_TSI_DEVICE,
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};
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struct apml_device_node {
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struct list_head list;
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struct kref ref;
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enum apml_device_type dev_type;
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union {
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struct apml_sbrmi_device *rmi_dev;
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struct apml_sbtsi_device *tsi_dev;
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};
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};
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/* Function declarations - available when APML_COMMON is built */
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#if IS_ENABLED(CONFIG_APML_COMMON)
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int apml_register_sbrmi_device(struct apml_sbrmi_device *rmi_dev);
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void apml_unregister_sbrmi_device(struct apml_sbrmi_device *rmi_dev);
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int apml_register_sbtsi_device(struct apml_sbtsi_device *tsi_dev);
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void apml_unregister_sbtsi_device(struct apml_sbtsi_device *tsi_dev);
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struct apml_device_node *apml_get_device_node(struct apml_device_node *node);
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void apml_put_device_node(struct apml_device_node *node);
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#else
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/* Stub functions when APML_COMMON is not available */
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static inline int apml_register_sbrmi_device(struct apml_sbrmi_device *rmi_dev)
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{
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return 0;
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}
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static inline void apml_unregister_sbrmi_device(struct apml_sbrmi_device *rmi_dev)
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{
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return 0;
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}
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static inline int apml_register_sbtsi_device(struct apml_sbtsi_device *tsi_dev)
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{
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return 0;
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}
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static inline void apml_unregister_sbtsi_device(struct apml_sbtsi_device *tsi_dev)
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{
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return 0
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}
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static inline struct apml_device_node *apml_get_device_node(struct apml_device_node *node)
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{
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return NULL;
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}
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static inline void apml_put_device_node(struct apml_device_node *node)
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{
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return 0;
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}
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#endif /* IS_ENABLED(CONFIG_APML_COMMON) */
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#endif /* _AMD_APML_COMMON_H_ */

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