[PATCH v10 1/7] firmware: smccc: Add an Arm SMCCC bus

@@ -1,4 +1,4 @@
 # SPDX-License-Identifier: GPL-2.0
 #
-obj-$(CONFIG_HAVE_ARM_SMCCC_DISCOVERY)	+= smccc.o kvm_guest.o
+obj-$(CONFIG_HAVE_ARM_SMCCC_DISCOVERY)	+= bus.o smccc.o kvm_guest.o
 obj-$(CONFIG_ARM_SMCCC_SOC_ID)	+= soc_id.o

@@ -0,0 +1,151 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2026 Arm Limited
+ */
+
+#include <linux/arm-smccc-bus.h>
+#include <linux/slab.h>
+
+static int arm_smccc_bus_match(struct device *dev,
+		const struct device_driver *drv)
+{
+	const struct arm_smccc_device_id *id_table;
+	struct arm_smccc_device *smccc_dev = to_arm_smccc_device(dev);
+
+	id_table = to_arm_smccc_driver(drv)->id_table;
+	if (!id_table)
+		return 0;
+
+	while (id_table->func_id) {
+		if (smccc_dev->func_id == id_table->func_id)
+			return 1;
+		id_table++;
+	}
+
+	return 0;
+}
+
+static int arm_smccc_bus_probe(struct device *dev)
+{
+	struct arm_smccc_driver *smccc_drv = to_arm_smccc_driver(dev->driver);
+
+	return smccc_drv->probe(to_arm_smccc_device(dev));
+}
+
+static void arm_smccc_bus_remove(struct device *dev)
+{
+	struct arm_smccc_driver *smcc_drv = to_arm_smccc_driver(dev->driver);
+
+	if (smcc_drv->remove)
+		smcc_drv->remove(to_arm_smccc_device(dev));
+}
+
+static int arm_smccc_bus_uevent(const struct device *dev,
+		struct kobj_uevent_env *env)
+{
+	const struct arm_smccc_device *smccc_dev = to_arm_smccc_device(dev);
+
+	return add_uevent_var(env, "MODALIAS=" ARM_SMCCC_MODULE_PREFIX "f%08X",
+			      smccc_dev->func_id);
+}
+
+static ssize_t modalias_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct arm_smccc_device *smccc_dev = to_arm_smccc_device(dev);
+
+	return sysfs_emit(buf, ARM_SMCCC_MODULE_PREFIX "f%08X\n",
+			  smccc_dev->func_id);
+}
+static DEVICE_ATTR_RO(modalias);
+
+static struct attribute *arm_smccc_device_attrs[] = {
+	&dev_attr_modalias.attr,
+	NULL,
+};
+ATTRIBUTE_GROUPS(arm_smccc_device);
+
+const struct bus_type arm_smccc_bus_type = {
+	.name = "arm_smccc",
+	.match = arm_smccc_bus_match,
+	.probe = arm_smccc_bus_probe,
+	.remove = arm_smccc_bus_remove,
+	.uevent = arm_smccc_bus_uevent,
+	.dev_groups = arm_smccc_device_groups,
+};
+EXPORT_SYMBOL_GPL(arm_smccc_bus_type);
+
+int arm_smccc_driver_register(struct arm_smccc_driver *driver,
+		struct module *owner, const char *mod_name)
+{
+	if (!driver->probe || !driver->id_table)
+		return -EINVAL;
+
+	driver->driver.bus = &arm_smccc_bus_type;
+	driver->driver.name = driver->name;
+	driver->driver.owner = owner;
+	driver->driver.mod_name = mod_name;
+
+	return driver_register(&driver->driver);
+}
+EXPORT_SYMBOL_GPL(arm_smccc_driver_register);
+
+void arm_smccc_driver_unregister(struct arm_smccc_driver *driver)
+{
+	driver_unregister(&driver->driver);
+}
+EXPORT_SYMBOL_GPL(arm_smccc_driver_unregister);
+
+static void arm_smccc_release_device(struct device *dev)
+{
+	struct arm_smccc_device *smccc_dev = to_arm_smccc_device(dev);
+
+	kfree(smccc_dev);
+}
+
+struct arm_smccc_device *arm_smccc_device_register(const char *name, u32 func_id)
+{
+	int ret;
+	struct arm_smccc_device *smccc_dev;
+
+	if (!name)
+		return ERR_PTR(-EINVAL);
+
+	smccc_dev = kzalloc_obj(*smccc_dev);
+	if (!smccc_dev)
+		return ERR_PTR(-ENOMEM);
+
+	smccc_dev->func_id = func_id;
+	smccc_dev->dev.bus = &arm_smccc_bus_type;
+	smccc_dev->dev.release = arm_smccc_release_device;
+
+	ret = dev_set_name(&smccc_dev->dev, "%s", name);
+	if (ret) {
+		kfree(smccc_dev);
+		return ERR_PTR(ret);
+	}
+
+	ret = device_register(&smccc_dev->dev);
+	if (ret) {
+		put_device(&smccc_dev->dev);
+		return ERR_PTR(ret);
+	}
+
+	return smccc_dev;
+}
+EXPORT_SYMBOL_GPL(arm_smccc_device_register);
+
+void arm_smccc_device_unregister(struct arm_smccc_device *smccc_dev)
+{
+	if (!smccc_dev)
+		return;
+
+	device_unregister(&smccc_dev->dev);
+}
+EXPORT_SYMBOL_GPL(arm_smccc_device_unregister);
+
+static int __init arm_smccc_bus_init(void)
+{
+	return bus_register(&arm_smccc_bus_type);
+}
+subsys_initcall(arm_smccc_bus_init);

@@ -0,0 +1,48 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2026 Arm Limited
+ */
+#ifndef __LINUX_ARM_SMCCC_BUS_H
+#define __LINUX_ARM_SMCCC_BUS_H
+
+#include <linux/device.h>
+#include <linux/device-id/arm_smccc.h>
+#include <linux/module.h>
+
+struct arm_smccc_device {
+	struct device dev;
+	u32 func_id;
+};
+
+#define to_arm_smccc_device(d) container_of(d, struct arm_smccc_device, dev)
+
+struct arm_smccc_driver {
+	struct device_driver driver;
+
+	const char *name;
+	int (*probe)(struct arm_smccc_device *sdev);
+	void (*remove)(struct arm_smccc_device *sdev);
+	const struct arm_smccc_device_id *id_table;
+};
+
+#define to_arm_smccc_driver(d) \
+	container_of_const(d, struct arm_smccc_driver, driver)
+
+int arm_smccc_driver_register(struct arm_smccc_driver *driver,
+		struct module *owner, const char *mod_name);
+void arm_smccc_driver_unregister(struct arm_smccc_driver *driver);
+struct arm_smccc_device *arm_smccc_device_register(const char *name, u32 func_id);
+void arm_smccc_device_unregister(struct arm_smccc_device *smcc_dev);
+
+#define arm_smccc_register(driver) \
+	arm_smccc_driver_register(driver, THIS_MODULE, KBUILD_MODNAME)
+#define arm_smccc_unregister(driver) \
+	arm_smccc_driver_unregister(driver)
+
+#define module_arm_smccc_driver(__arm_smccc_driver) \
+	module_driver(__arm_smccc_driver, arm_smccc_register, \
+		      arm_smccc_unregister)
+
+extern const struct bus_type arm_smccc_bus_type;
+
+#endif /* __LINUX_ARM_SMCCC_BUS_H */

@@ -0,0 +1,15 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __LINUX_DEVICE_ID_ARM_SMCCC_H
+#define __LINUX_DEVICE_ID_ARM_SMCCC_H
+
+#define ARM_SMCCC_MODULE_PREFIX "arm_smccc:"
+
+/**
+ * struct arm_smccc_device_id - Arm SMCCC bus device identifier
+ * @func_id: SMCCC function identifier
+ */
+struct arm_smccc_device_id {
+	__u32 func_id;
+};
+
+#endif /* __LINUX_DEVICE_ID_ARM_SMCCC_H */

@@ -16,6 +16,7 @@
 #include "device-id/amba.h"
 #include "device-id/ap.h"
 #include "device-id/apr.h"
+#include "device-id/arm_smccc.h"
 #include "device-id/auxiliary.h"
 #include "device-id/bcma.h"
 #include "device-id/ccw.h"

@@ -254,6 +254,9 @@ int main(void)
 	DEVID(auxiliary_device_id);
 	DEVID_FIELD(auxiliary_device_id, name);
 
+	DEVID(arm_smccc_device_id);
+	DEVID_FIELD(arm_smccc_device_id, func_id);
+
 	DEVID(ssam_device_id);
 	DEVID_FIELD(ssam_device_id, match_flags);
 	DEVID_FIELD(ssam_device_id, domain);

@@ -1349,6 +1349,13 @@ static void do_auxiliary_entry(struct module *mod, void *symval)
 	module_alias_printf(mod, false, AUXILIARY_MODULE_PREFIX "%s", *name);
 }
 
+static void do_arm_smccc_entry(struct module *mod, void *symval)
+{
+	DEF_FIELD(symval, arm_smccc_device_id, func_id);
+
+	module_alias_printf(mod, false, ARM_SMCCC_MODULE_PREFIX "f%08X", func_id);
+}
+
 /*
  * Looks like: ssam:dNcNtNiNfN
  *

@@ -1519,6 +1526,7 @@ static const struct devtable devtable[] = {
 	{"mhi", SIZE_mhi_device_id, do_mhi_entry},
 	{"mhi_ep", SIZE_mhi_device_id, do_mhi_ep_entry},
 	{"auxiliary", SIZE_auxiliary_device_id, do_auxiliary_entry},
+	{"arm_smccc", SIZE_arm_smccc_device_id, do_arm_smccc_entry},
 	{"ssam", SIZE_ssam_device_id, do_ssam_entry},
 	{"dfl", SIZE_dfl_device_id, do_dfl_entry},
 	{"ishtp", SIZE_ishtp_device_id, do_ishtp_entry},