[PATCH v6 6/7] i3c: hub: Add support for the I3C interface in the I3C hub

Lakshay Piplani
2026-03-10T06:57:43Z

Add virtual I3C bus support for the hub and provide interface to enable
or disable downstream ports.

Signed-off-by: Aman Kumar Pandey <aman.kumarpandey@nxp.com>
Signed-off-by: Vikash Bansal <vikash.bansal@nxp.com>
Signed-off-by: Lakshay Piplani <lakshay.piplani@nxp.com>

---
Changes in v6:
- Add support for the generic I3C interface in the I3C Hub
---
---
MAINTAINERS | 3 +
drivers/i3c/Kconfig | 15 ++
drivers/i3c/Makefile | 1 +
drivers/i3c/hub.c | 459 ++++++++++++++++++++++++++++++++++++++++
include/linux/i3c/hub.h | 107 ++++++++++
5 files changed, 585 insertions(+)
create mode 100644 drivers/i3c/hub.c
create mode 100644 include/linux/i3c/hub.h

diff --git a/MAINTAINERS b/MAINTAINERS
index 2fc44b489ea1..7613b4b59290 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -19110,12 +19110,15 @@ F: drivers/ptp/ptp_netc.c
NXP P3H2X4X I3C-HUB DRIVER
M: Vikash Bansal <vikash.bansal@nxp.com>
M: Aman Kumar Pandey <aman.kumarpandey@nxp.com>
+M: Lakshay Piplani <lakshay.piplani@nxp.com>
L: linux-kernel@vger.kernel.org
L: linux-i3c-owner@lists.infradead.org
S: Maintained
F: Documentation/devicetree/bindings/i3c/nxp,p3h2840.yaml
+F: drivers/i3c/hub.c
F: drivers/mfd/p3h2840.c
F: drivers/regulator/p3h2840_i3c_hub_regulator.c
+F: include/linux/i3c/hub.h
F: include/linux/mfd/p3h2840.h

NXP PF5300/PF5301/PF5302 PMIC REGULATOR DEVICE DRIVER
diff --git a/drivers/i3c/Kconfig b/drivers/i3c/Kconfig
index 30a441506f61..889d781f099b 100644
--- a/drivers/i3c/Kconfig
+++ b/drivers/i3c/Kconfig
@@ -21,4 +21,19 @@ menuconfig I3C

if I3C
source "drivers/i3c/master/Kconfig"
+
+config I3C_HUB
+ bool "I3C Hub Support"
+ depends on I3C
+ help
+ Enable support for the I3C interface in hub devices.
+
+ This option adds virtual I3C bus support for hubs by creating
+ virtual master controllers for downstream ports and forwarding
+ bus operations through the hub device. It also provides an
+ interface used by hub drivers to enable or disable downstream
+ ports during bus transactions.
+
+ Say Y here if your platform includes an I3C hub device
+
endif # I3C
diff --git a/drivers/i3c/Makefile b/drivers/i3c/Makefile
index 11982efbc6d9..9ddee56a6338 100644
--- a/drivers/i3c/Makefile
+++ b/drivers/i3c/Makefile
@@ -2,3 +2,4 @@
i3c-y := device.o master.o
obj-$(CONFIG_I3C) += i3c.o
obj-$(CONFIG_I3C) += master/
+obj-$(CONFIG_I3C_HUB) += hub.o
diff --git a/drivers/i3c/hub.c b/drivers/i3c/hub.c
new file mode 100644
index 000000000000..9cdea8635327
--- /dev/null
+++ b/drivers/i3c/hub.c
@@ -0,0 +1,459 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright 2026 NXP
+ * Generic I3C Hub core implementing virtual controller operations.
+ */
+#include <linux/i3c/device.h>
+#include <linux/i3c/hub.h>
+
+#include "internals.h"
+
+/**
+ * i3c_hub_master_bus_init() - Bind controller to hub device
+ * @controller: Virtual controller for a hub port
+ *
+ * Associates the virtual controller with the hub device descriptor so that
+ * transfers are executed through the hub on the parent bus.
+ */
+static int i3c_hub_master_bus_init(struct i3c_master_controller *controller)
+{
+ struct i3c_hub_controller *hub_controller;
+ struct i3c_hub *hub;
+
+ hub_controller = dev_get_drvdata(&controller->dev);
+ if (!hub_controller || !hub_controller->hub)
+ return -ENODEV;
+
+ hub = hub_controller->hub;
+
+ if (!hub->hub_dev)
+ return -ENODEV;
+
+ controller->this = hub->hub_dev->desc;
+ return 0;
+}
+
+static void i3c_hub_master_bus_cleanup(struct i3c_master_controller *controller)
+{
+ controller->this = NULL;
+}
+
+static int i3c_hub_attach_i3c_dev(struct i3c_dev_desc *dev)
+{
+ return 0;
+}
+
+static int i3c_hub_reattach_i3c_dev(struct i3c_dev_desc *dev, u8 old_dyn_addr)
+{
+ return 0;
+}
+
+static void i3c_hub_detach_i3c_dev(struct i3c_dev_desc *dev)
+{
+}
+
+/**
+ * i3c_hub_do_daa() - Perform DAA via hub port
+ * @hub: Hub instance
+ * @controller: Virtual controller for a hub port
+ *
+ * Enables the port connection, performs DAA on the parent controller,
+ * then disables the connection.
+ */
+static int i3c_hub_do_daa(struct i3c_hub *hub,
+ struct i3c_master_controller *controller)
+{
+ int ret;
+
+ if (!hub || !hub->parent)
+ return -ENODEV;
+
+ i3c_hub_enable_port(controller);
+ ret = i3c_master_do_daa(hub->parent);
+ i3c_hub_disable_port(controller);
+
+ return ret;
+}
+
+static bool i3c_hub_supports_ccc_cmd(struct i3c_hub *hub,
+ const struct i3c_ccc_cmd *cmd)
+{
+ return i3c_master_supports_ccc_cmd(hub->parent, cmd);
+}
+
+/**
+ * i3c_hub_send_ccc_cmd() - Send CCC through hub port
+ * @hub: Hub instance
+ * @controller: Virtual controller
+ * @cmd: CCC command
+ *
+ * Enables the port connection while issuing CCC on the parent controller.
+ */
+static int i3c_hub_send_ccc_cmd(struct i3c_hub *hub,
+ struct i3c_master_controller *controller,
+ struct i3c_ccc_cmd *cmd)
+{
+ int ret;
+
+ if (!hub || !hub->parent)
+ return -ENODEV;
+
+ i3c_hub_enable_port(controller);
+ ret = i3c_master_send_ccc_cmd(hub->parent, cmd);
+ i3c_hub_disable_port(controller);
+
+ return ret;
+}
+
+/**
+ * i3c_hub_master_priv_xfers() - Execute private transfers via hub
+ * @dev: Target device descriptor
+ * @xfers: Transfer array
+ * @nxfers: Number of transfers
+ *
+ * Handles address adjustment and forwards private transfers through the hub
+ * device.
+ */
+static int i3c_hub_master_priv_xfers(struct i3c_dev_desc *dev,
+ struct i3c_xfer *xfers,
+ int nxfers,
+ enum i3c_xfer_mode mode)
+{
+ struct i3c_master_controller *controller = i3c_dev_get_master(dev);
+ struct i3c_hub_controller *hub_controller;
+ struct i3c_dev_desc *hub_dev;
+ u8 hub_addr, target_addr;
+ struct i3c_hub *hub;
+ int ret;
+
+ hub_controller = dev_get_drvdata(&controller->dev);
+ if (!hub_controller || !hub_controller->hub)
+ return -ENODEV;
+
+ hub = hub_controller->hub;
+
+ if (!hub->hub_dev)
+ return -ENODEV;
+
+ hub_dev = hub->hub_dev->desc;
+
+ i3c_hub_enable_port(controller);
+
+ hub_addr = hub_dev->info.dyn_addr ?
+ hub_dev->info.dyn_addr : hub_dev->info.static_addr;
+
+ target_addr = dev->info.dyn_addr ?
+ dev->info.dyn_addr : dev->info.static_addr;
+
+ if (hub_addr != target_addr) {
+ hub_dev->info.dyn_addr = target_addr;
+ ret = i3c_master_reattach_i3c_dev(hub_dev, target_addr);
+ if (ret)
+ goto disable;
+ }
+
+ ret = i3c_device_do_xfers(hub->hub_dev, xfers, nxfers, mode);
+
+ if (hub_addr != target_addr) {
+ hub_dev->info.dyn_addr = hub_addr;
+ ret |= i3c_master_reattach_i3c_dev(hub_dev, hub_addr);
+ }
+
+disable:
+ i3c_hub_disable_port(controller);
+ return ret;
+}
+
+static int i3c_hub_attach_i2c_dev(struct i2c_dev_desc *dev)
+{
+ return 0;
+}
+
+static void i3c_hub_detach_i2c_dev(struct i2c_dev_desc *dev)
+{
+}
+
+static int i3c_hub_i2c_xfers(struct i2c_dev_desc *dev,
+ struct i2c_msg *xfers, int nxfers)
+{
+ return 0;
+}
+
+static int i3c_hub_master_do_daa(struct i3c_master_controller *controller)
+{
+ struct i3c_hub_controller *hub_controller;
+ struct i3c_hub *hub;
+
+ hub_controller = dev_get_drvdata(&controller->dev);
+ if (!hub_controller || !hub_controller->hub)
+ return -ENODEV;
+
+ hub = hub_controller->hub;
+
+ return i3c_hub_do_daa(hub, controller);
+}
+
+static int i3c_hub_master_send_ccc_cmd(struct i3c_master_controller *controller,
+ struct i3c_ccc_cmd *cmd)
+{
+ struct i3c_hub_controller *hub_controller;
+ struct i3c_hub *hub;
+
+ hub_controller = dev_get_drvdata(&controller->dev);
+ if (!hub_controller || !hub_controller->hub)
+ return -ENODEV;
+
+ hub = hub_controller->hub;
+
+ if (!hub->parent)
+ return -ENODEV;
+
+ if (cmd->id == I3C_CCC_RSTDAA(true))
+ return 0;
+
+ return i3c_hub_send_ccc_cmd(hub, controller, cmd);
+}
+
+static bool i3c_hub_master_supports_ccc_cmd(struct i3c_master_controller *controller,
+ const struct i3c_ccc_cmd *cmd)
+{
+ struct i3c_hub_controller *hub_controller;
+ struct i3c_hub *hub;
+
+ hub_controller = dev_get_drvdata(&controller->dev);
+ if (!hub_controller || !hub_controller->hub)
+ return -ENODEV;
+
+ hub = hub_controller->hub;
+
+ return i3c_hub_supports_ccc_cmd(hub, cmd);
+}
+
+/**
+ * i3c_hub_request_ibi() - Request IBI through parent controller
+ * @desc: Target device descriptor
+ * @req: IBI setup
+ *
+ * Temporarily updates parent controller context to request IBI for a device
+ * connected through the hub.
+ */
+static int i3c_hub_request_ibi(struct i3c_dev_desc *desc,
+ const struct i3c_ibi_setup *req)
+{
+ struct i3c_master_controller *controller = i3c_dev_get_master(desc);
+ struct i3c_hub_controller *hub_controller;
+ struct i3c_master_controller *orig_parent;
+ struct i3c_master_controller *parent;
+ struct i3c_hub *hub;
+ int ret;
+
+ hub_controller = dev_get_drvdata(&controller->dev);
+ if (!hub_controller || !hub_controller->hub)
+ return -ENODEV;
+
+ hub = hub_controller->hub;
+
+ if (!hub->parent)
+ return -ENODEV;
+
+ parent = hub->parent;
+
+ orig_parent = i3c_hub_update_desc_parent(&desc->common, parent);
+
+ ret = i3c_master_direct_attach_i3c_dev(parent, desc);
+ if (ret) {
+ i3c_hub_restore_desc_parent(&desc->common, orig_parent);
+ return ret;
+ }
+
+ mutex_unlock(&desc->ibi_lock);
+ kfree(desc->ibi);
+ desc->ibi = NULL;
+ ret = i3c_dev_request_ibi_locked(desc, req);
+ mutex_lock(&desc->ibi_lock);
+
+ i3c_hub_restore_desc_parent(&desc->common, orig_parent);
+
+ return ret;
+}
+
+static void i3c_hub_free_ibi(struct i3c_dev_desc *desc)
+{
+ struct i3c_master_controller *controller = i3c_dev_get_master(desc);
+ struct i3c_hub_controller *hub_controller;
+ struct i3c_master_controller *orig_parent;
+ struct i3c_master_controller *parent;
+ struct i3c_hub *hub;
+
+ hub_controller = dev_get_drvdata(&controller->dev);
+ if (!hub_controller || !hub_controller->hub)
+ return;
+
+ hub = hub_controller->hub;
+
+ parent = hub->parent;
+
+ i3c_hub_enable_port(controller);
+
+ orig_parent = i3c_hub_update_desc_parent(&desc->common, parent);
+ i3c_master_direct_detach_i3c_dev(desc);
+ mutex_unlock(&desc->ibi_lock);
+ i3c_dev_free_ibi_locked(desc);
+ mutex_lock(&desc->ibi_lock);
+ i3c_hub_restore_desc_parent(&desc->common, orig_parent);
+
+ i3c_hub_disable_port(controller);
+}
+
+/**
+ * i3c_hub_enable_ibi() - Enable IBI via hub port
+ * @desc: Target device descriptor
+ *
+ * Enables port connection and forwards the IBI enable request to the parent
+ * controller.
+ */
+static int i3c_hub_enable_ibi(struct i3c_dev_desc *desc)
+{
+ struct i3c_master_controller *controller = i3c_dev_get_master(desc);
+ struct i3c_hub_controller *hub_controller;
+ struct i3c_master_controller *orig_parent;
+ struct i3c_master_controller *parent;
+ struct i3c_hub *hub;
+ int ret;
+
+ hub_controller = dev_get_drvdata(&controller->dev);
+ if (!hub_controller || !hub_controller->hub)
+ return -ENODEV;
+
+ hub = hub_controller->hub;
+
+ if (!hub->parent)
+ return -ENODEV;
+
+ parent = hub->parent;
+
+ i3c_hub_enable_port(controller);
+
+ orig_parent = i3c_hub_update_desc_parent(&desc->common, parent);
+
+ down_write(&parent->bus.lock);
+ mutex_unlock(&desc->ibi_lock);
+ ret = i3c_dev_enable_ibi_locked(desc);
+ mutex_lock(&desc->ibi_lock);
+ up_write(&parent->bus.lock);
+
+ i3c_hub_restore_desc_parent(&desc->common, orig_parent);
+
+ i3c_hub_disable_port(controller);
+
+ return ret;
+}
+
+/**
+ * i3c_hub_disable_ibi() - Disable IBI via hub port
+ * @desc: Target device descriptor
+ *
+ * Enables port connection and forwards the IBI disable request to the parent
+ * controller.
+ */
+static int i3c_hub_disable_ibi(struct i3c_dev_desc *desc)
+{
+ struct i3c_master_controller *controller = i3c_dev_get_master(desc);
+ struct i3c_hub_controller *hub_controller;
+ struct i3c_master_controller *orig_parent;
+ struct i3c_master_controller *parent;
+ struct i3c_hub *hub;
+ int ret;
+
+ hub_controller = dev_get_drvdata(&controller->dev);
+ if (!hub_controller || !hub_controller->hub)
+ return -ENODEV;
+
+ hub = hub_controller->hub;
+
+ if (!hub->parent)
+ return -ENODEV;
+
+ parent = hub->parent;
+
+ i3c_hub_enable_port(controller);
+
+ orig_parent = i3c_hub_update_desc_parent(&desc->common, parent);
+
+ down_write(&parent->bus.lock);
+ mutex_unlock(&desc->ibi_lock);
+ ret = i3c_dev_disable_ibi_locked(desc);
+ mutex_lock(&desc->ibi_lock);
+ up_write(&parent->bus.lock);
+
+ i3c_hub_restore_desc_parent(&desc->common, orig_parent);
+
+ i3c_hub_disable_port(controller);
+
+ return ret;
+}
+
+static void i3c_hub_recycle_ibi_slot(struct i3c_dev_desc *desc,
+ struct i3c_ibi_slot *slot)
+{
+}
+
+static const struct i3c_master_controller_ops i3c_hub_master_ops_data = {
+ .bus_init = i3c_hub_master_bus_init,
+ .bus_cleanup = i3c_hub_master_bus_cleanup,
+ .attach_i3c_dev = i3c_hub_attach_i3c_dev,
+ .reattach_i3c_dev = i3c_hub_reattach_i3c_dev,
+ .detach_i3c_dev = i3c_hub_detach_i3c_dev,
+ .do_daa = i3c_hub_master_do_daa,
+ .supports_ccc_cmd = i3c_hub_master_supports_ccc_cmd,
+ .send_ccc_cmd = i3c_hub_master_send_ccc_cmd,
+ .i3c_xfers = i3c_hub_master_priv_xfers,
+ .attach_i2c_dev = i3c_hub_attach_i2c_dev,
+ .detach_i2c_dev = i3c_hub_detach_i2c_dev,
+ .i2c_xfers = i3c_hub_i2c_xfers,
+ .request_ibi = i3c_hub_request_ibi,
+ .free_ibi = i3c_hub_free_ibi,
+ .enable_ibi = i3c_hub_enable_ibi,
+ .disable_ibi = i3c_hub_disable_ibi,
+ .recycle_ibi_slot = i3c_hub_recycle_ibi_slot,
+};
+
+/**
+ * i3c_hub_init() - Initialize hub context
+ * @hub: Hub instance
+ * @parent: Parent I3C master controller
+ * @ops: Vendor callbacks
+ * @hub_dev: I3C hub device
+ */
+struct i3c_hub *i3c_hub_init(struct i3c_master_controller *parent,
+ const struct i3c_hub_ops *ops,
+ struct i3c_device *hub_dev)
+{
+ struct i3c_hub *hub;
+
+ hub = devm_kzalloc(&hub_dev->dev,
+ sizeof(*hub),
+ GFP_KERNEL);
+
+ if (!hub)
+ return ERR_PTR(-ENOMEM);
+
+ hub->parent = parent;
+ hub->ops = ops;
+ hub->hub_dev = hub_dev;
+
+ return hub;
+}
+EXPORT_SYMBOL_GPL(i3c_hub_init);
+
+const struct i3c_master_controller_ops *i3c_hub_master_ops(void)
+{
+ return &i3c_hub_master_ops_data;
+}
+EXPORT_SYMBOL_GPL(i3c_hub_master_ops);
+
+MODULE_AUTHOR("Aman Kumar Pandey <aman.kumarpandey@nxp.com>");
+MODULE_AUTHOR("Vikash Bansal <vikash.bansal@nxp.com>");
+MODULE_AUTHOR("Lakshay Piplani <lakshay.piplani@nxp.com>");
+MODULE_DESCRIPTION("Generic I3C hub support");
+MODULE_LICENSE("GPL");
diff --git a/include/linux/i3c/hub.h b/include/linux/i3c/hub.h
new file mode 100644
index 000000000000..b685d4d3cc7e
--- /dev/null
+++ b/include/linux/i3c/hub.h
@@ -0,0 +1,107 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright 2026 NXP
+ * Generic hub definitions and helper interfaces.
+ */
+#ifndef _LINUX_I3C_HUB_H
+#define _LINUX_I3C_HUB_H
+
+#include <linux/i3c/master.h>
+
+static inline struct i3c_master_controller *
+i3c_hub_update_desc_parent(struct i3c_i2c_dev_desc *desc,
+ struct i3c_master_controller *parent)
+{
+ struct i3c_master_controller *orig_parent = desc->master;
+
+ desc->master = parent;
+ return orig_parent;
+}
+
+static inline void
+i3c_hub_restore_desc_parent(struct i3c_i2c_dev_desc *desc,
+ struct i3c_master_controller *parent)
+{
+ desc->master = parent;
+}
+
+/**
+ * struct i3c_hub - Generic I3C hub context
+ * @parent: Parent I3C master controller
+ * @ops: Vendor callbacks for port connection control
+ * @hub_dev: I3C device representing the hub on the parent bus
+ */
+struct i3c_hub {
+ struct i3c_master_controller *parent;
+ const struct i3c_hub_ops *ops;
+ struct i3c_device *hub_dev;
+};
+
+struct i3c_hub_controller {
+ struct i3c_master_controller *parent;
+ struct i3c_master_controller controller;
+ struct i3c_hub *hub;
+};
+
+struct i3c_hub_ops {
+ void (*enable_port)(struct i3c_master_controller *controller);
+ void (*disable_port)(struct i3c_master_controller *controller);
+};
+
+/**
+ * i3c_hub_enable_port() - Enable hub connection for a controller
+ * @controller: Virtual controller representing a hub port
+ *
+ * Retrieves hub context from controller drvdata and invokes the vendor
+ * callback to enable the associated port connection.
+ */
+static inline void i3c_hub_enable_port(struct i3c_master_controller *controller)
+{
+ struct i3c_hub_controller *hub_controller;
+ struct i3c_hub *hub;
+
+ hub_controller = dev_get_drvdata(&controller->dev);
+ if (!hub_controller || !hub_controller->hub)
+ return;
+
+ hub = hub_controller->hub;
+
+ if (hub && hub->ops && hub->ops->enable_port)
+ hub->ops->enable_port(controller);
+}
+
+/**
+ * i3c_hub_disable_port() - Disable hub connection for a controller
+ * @controller: Virtual controller representing a hub port
+ *
+ * Retrieves hub context from controller drvdata and invokes the vendor
+ * callback to disable the associated port connection.
+ */
+static inline void i3c_hub_disable_port(struct i3c_master_controller *controller)
+{
+ struct i3c_hub_controller *hub_controller;
+ struct i3c_hub *hub;
+
+ hub_controller = dev_get_drvdata(&controller->dev);
+ if (!hub_controller || !hub_controller->hub)
+ return;
+
+ hub = hub_controller->hub;
+
+ if (hub && hub->ops && hub->ops->disable_port)
+ hub->ops->disable_port(controller);
+}
+
+/**
+ * i3c_hub_master_ops() - Return virtual controller ops for hub ports
+ *
+ * Provides i3c_master_controller_ops used by controllers created for hub
+ * ports.
+ */
+const struct i3c_master_controller_ops *i3c_hub_master_ops(void);
+
+struct i3c_hub *i3c_hub_init(struct i3c_master_controller *parent,
+ const struct i3c_hub_ops *ops,
+ struct i3c_device *hub_dev);
+
+#endif
--
2.25.1