From 718ba914a00cde53f5df0c3de369333d0ddcd5a5 Mon Sep 17 00:00:00 2001
From: Samuel Morris <scmorris.dev@gmail.com>
Date: Mon, 1 Jun 2026 14:32:17 -0700
Subject: [PATCH 01/22] extcon: Add STM32 SPI IPC driver

Add a custom SPI client driver that functions as an extcon event
provider. This driver communicates with an external STM32 co-processor
over SPI using an attention line (interrupt) to propagate USB cable
events.

It registers separate virtual extcon sub-devices for each connector,
allowing ChipIdea OTG controllers to switch between Host/Peripheral
roles. A debugfs simulation interface is also exposed for runtime testing.
---
 drivers/extcon/Kconfig            |   7 +
 drivers/extcon/Makefile           |   1 +
 drivers/extcon/extcon-stm32-ipc.c | 292 ++++++++++++++++++++++++++++++
 3 files changed, 300 insertions(+)
 create mode 100644 drivers/extcon/extcon-stm32-ipc.c

diff --git a/drivers/extcon/Kconfig b/drivers/extcon/Kconfig
index cf472e44c5ff9..8852425b68fba 100644
--- a/drivers/extcon/Kconfig
+++ b/drivers/extcon/Kconfig
@@ -176,6 +176,13 @@ config EXTCON_USB_GPIO
 	  Say Y here to enable GPIO based USB cable detection extcon support.
 	  Used typically if GPIO is used for USB ID pin detection.
 
+config EXTCON_STM32_SPI_IPC
+	tristate "STM32 SPI IPC and Virtual Extcon support"
+	depends on SPI
+	help
+	  Say Y here to enable the STM32 to i.MX8MM SPI IPC and Virtual Extcon
+	  driver, which handles USB connection/cable event notifications over SPI.
+
 config EXTCON_USBC_CROS_EC
 	tristate "ChromeOS Embedded Controller EXTCON support"
 	depends on CROS_EC
diff --git a/drivers/extcon/Makefile b/drivers/extcon/Makefile
index 1b390d934ca92..b962d043fd804 100644
--- a/drivers/extcon/Makefile
+++ b/drivers/extcon/Makefile
@@ -23,5 +23,6 @@ obj-$(CONFIG_EXTCON_QCOM_SPMI_MISC) += extcon-qcom-spmi-misc.o
 obj-$(CONFIG_EXTCON_RT8973A)	+= extcon-rt8973a.o
 obj-$(CONFIG_EXTCON_SM5502)	+= extcon-sm5502.o
 obj-$(CONFIG_EXTCON_USB_GPIO)	+= extcon-usb-gpio.o
+obj-$(CONFIG_EXTCON_STM32_SPI_IPC)	+= extcon-stm32-ipc.o
 obj-$(CONFIG_EXTCON_USBC_CROS_EC) += extcon-usbc-cros-ec.o
 obj-$(CONFIG_EXTCON_USBC_TUSB320) += extcon-usbc-tusb320.o
diff --git a/drivers/extcon/extcon-stm32-ipc.c b/drivers/extcon/extcon-stm32-ipc.c
new file mode 100644
index 0000000000000..ad70407cbb0c7
--- /dev/null
+++ b/drivers/extcon/extcon-stm32-ipc.c
@@ -0,0 +1,292 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * drivers/extcon/extcon-stm32-ipc.c - STM32 SPI IPC and Virtual Extcon Driver
+ *
+ * Copyright (C) 2026 MultiTracks
+ */
+
+#include <linux/module.h>
+#include <linux/spi/spi.h>
+#include <linux/extcon-provider.h>
+#include <linux/interrupt.h>
+#include <linux/gpio/consumer.h>
+#include <linux/platform_device.h>
+#include <linux/of_platform.h>
+#include <linux/slab.h>
+#include <linux/debugfs.h>
+#include <linux/mutex.h>
+
+#define DRIVER_NAME "stm-spi-ipc"
+
+/* Protocol constants */
+#define STM_IPC_MSG_MAGIC   0x5A
+#define MSG_TYPE_USB_EVENT  0x01
+
+struct stm_ipc_packet {
+	u8 magic;
+	u8 type;
+	u8 length;
+	u8 port;
+	u8 state; /* 0 = disconnected, 1 = peripheral (VBUS), 2 = host (ID) */
+	u8 crc;
+} __packed;
+
+/* Parent SPI controller private structure */
+struct stm_ipc_priv {
+	struct spi_device *spi;
+	struct mutex lock;
+	struct dentry *debugfs_root;
+};
+
+/* Child connector platform device private structure */
+struct stm_connector_priv {
+	struct extcon_dev *edev;
+	u32 port_id;
+};
+
+static const unsigned int stm_usb_cable[] = {
+	EXTCON_USB,
+	EXTCON_USB_HOST,
+	EXTCON_NONE,
+};
+
+/* Helper to update extcon state based on STM32 reporting */
+static void stm_ipc_update_state(struct extcon_dev *edev, u8 state)
+{
+	switch (state) {
+	case 0: /* Disconnected */
+		extcon_set_state_sync(edev, EXTCON_USB, false);
+		extcon_set_state_sync(edev, EXTCON_USB_HOST, false);
+		break;
+	case 1: /* Peripheral Mode (VBUS present) */
+		extcon_set_state_sync(edev, EXTCON_USB_HOST, false);
+		extcon_set_state_sync(edev, EXTCON_USB, true);
+		break;
+	case 2: /* Host Mode (ID ground) */
+		extcon_set_state_sync(edev, EXTCON_USB, false);
+		extcon_set_state_sync(edev, EXTCON_USB_HOST, true);
+		break;
+	default:
+		break;
+	}
+}
+
+/* Callback used to find and update state of correct child platform device */
+static int match_and_update_state(struct device *dev, void *data)
+{
+	struct stm_connector_priv *priv = dev_get_drvdata(dev);
+	u8 *port_info = data;
+	u8 port_id = port_info[0];
+	u8 state = port_info[1];
+
+	if (priv && priv->port_id == port_id) {
+		stm_ipc_update_state(priv->edev, state);
+		return 1; /* Found and processed, stop iteration */
+	}
+	return 0;
+}
+
+/* Threaded IRQ Handler (safe to perform sleeping SPI transfers) */
+static irqreturn_t stm_ipc_threaded_irq(int irq, void *dev_id)
+{
+	struct stm_ipc_priv *priv = dev_id;
+	struct stm_ipc_packet tx_buf = {0};
+	struct stm_ipc_packet rx_buf = {0};
+	struct spi_transfer t = {
+		.tx_buf = &tx_buf,
+		.rx_buf = &rx_buf,
+		.len = sizeof(struct stm_ipc_packet),
+	};
+	struct spi_message m;
+	int ret;
+
+	mutex_lock(&priv->lock);
+
+	spi_message_init(&m);
+	spi_message_add_tail(&t, &m);
+	ret = spi_sync(priv->spi, &m);
+	if (ret < 0) {
+		dev_err(&priv->spi->dev, "SPI sync transfer failed: %d\n", ret);
+		goto out;
+	}
+
+	/* Validate packet */
+	if (rx_buf.magic != STM_IPC_MSG_MAGIC) {
+		dev_warn_ratelimited(&priv->spi->dev, "Invalid magic byte: 0x%02x\n", rx_buf.magic);
+		goto out;
+	}
+
+	/* Process USB event */
+	if (rx_buf.type == MSG_TYPE_USB_EVENT) {
+		u8 port_info[2] = { rx_buf.port, rx_buf.state };
+
+		dev_info(&priv->spi->dev, "USB Event from STM32 on Port %d: State %d\n", rx_buf.port, rx_buf.state);
+		device_for_each_child(&priv->spi->dev, port_info, match_and_update_state);
+	}
+
+out:
+	mutex_unlock(&priv->lock);
+	return IRQ_HANDLED;
+}
+
+/* Debugfs Simulation Entry (for mocking events) */
+static int stm_ipc_sim_write(void *data, u64 val)
+{
+	struct stm_connector_priv *priv = data;
+
+	if (val > 2)
+		return -EINVAL;
+
+	stm_ipc_update_state(priv->edev, (u8)val);
+	return 0;
+}
+DEFINE_DEBUGFS_ATTRIBUTE(stm_ipc_sim_fops, NULL, stm_ipc_sim_write, "%llu\n");
+
+/* Child Connector Platform Device Probe */
+static int stm_usb_connector_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct stm_connector_priv *priv;
+	int ret;
+
+	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	ret = of_property_read_u32(dev->of_node, "port-id", &priv->port_id);
+	if (ret) {
+		dev_err(dev, "Missing 'port-id' property\n");
+		return ret;
+	}
+
+	priv->edev = devm_extcon_dev_allocate(dev, stm_usb_cable);
+	if (IS_ERR(priv->edev))
+		return PTR_ERR(priv->edev);
+
+	ret = devm_extcon_dev_register(dev, priv->edev);
+	if (ret) {
+		dev_err(dev, "Failed to register extcon device: %d\n", ret);
+		return ret;
+	}
+
+	platform_set_drvdata(pdev, priv);
+
+	/* Set up DebugFS for this virtual connector for runtime simulation */
+	struct stm_ipc_priv *parent_priv = dev_get_drvdata(dev->parent);
+	if (parent_priv && parent_priv->debugfs_root) {
+		char name[32];
+		snprintf(name, sizeof(name), "usb%d_sim", priv->port_id + 1);
+		debugfs_create_file(name, 0200, parent_priv->debugfs_root, priv, &stm_ipc_sim_fops);
+	}
+
+	dev_info(dev, "Registered virtual USB connector on Port %d\n", priv->port_id);
+	return 0;
+}
+
+static const struct of_device_id stm_usb_connector_of_match[] = {
+	{ .compatible = "multitracks,stm32-usb-connector" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, stm_usb_connector_of_match);
+
+static struct platform_driver stm_usb_connector_driver = {
+	.probe = stm_usb_connector_probe,
+	.driver = {
+		.name = "stm32-usb-connector",
+		.of_match_table = stm_usb_connector_of_match,
+	},
+};
+
+/* Parent SPI Driver Probe */
+static int stm_ipc_probe(struct spi_device *spi)
+{
+	struct stm_ipc_priv *priv;
+	int ret;
+
+	priv = devm_kzalloc(&spi->dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	priv->spi = spi;
+	mutex_init(&priv->lock);
+	spi_set_drvdata(spi, priv);
+
+	/* Initialize DebugFS root directory under /sys/kernel/debug/stm_ipc */
+	priv->debugfs_root = debugfs_create_dir("stm_ipc", NULL);
+
+	/* Populate subnodes as platform devices (this probes the connector sub-drivers) */
+	ret = devm_of_platform_populate(&spi->dev);
+	if (ret) {
+		dev_err(&spi->dev, "Failed to populate child connectors: %d\n", ret);
+		goto err_debugfs;
+	}
+
+	/* Request Attention Pin Interrupt */
+	if (spi->irq > 0) {
+		ret = devm_request_threaded_irq(&spi->dev, spi->irq, NULL,
+						stm_ipc_threaded_irq,
+						IRQF_TRIGGER_FALLING | IRQF_ONESHOT,
+						DRIVER_NAME, priv);
+		if (ret) {
+			dev_err(&spi->dev, "Failed to request threaded IRQ: %d\n", ret);
+			goto err_debugfs;
+		}
+	}
+
+	dev_info(&spi->dev, "STM32 SPI IPC Core initialized\n");
+	return 0;
+
+err_debugfs:
+	debugfs_remove_recursive(priv->debugfs_root);
+	return ret;
+}
+
+static void stm_ipc_remove(struct spi_device *spi)
+{
+	struct stm_ipc_priv *priv = spi_get_drvdata(spi);
+	debugfs_remove_recursive(priv->debugfs_root);
+}
+
+static const struct of_device_id stm_ipc_of_match[] = {
+	{ .compatible = "multitracks,stm32-spi-ipc" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, stm_ipc_of_match);
+
+static struct spi_driver stm_ipc_driver = {
+	.driver = {
+		.name = DRIVER_NAME,
+		.of_match_table = stm_ipc_of_match,
+	},
+	.probe = stm_ipc_probe,
+	.remove = stm_ipc_remove,
+};
+
+static int __init stm_ipc_init(void)
+{
+	int ret;
+
+	ret = spi_register_driver(&stm_ipc_driver);
+	if (ret)
+		return ret;
+
+	ret = platform_driver_register(&stm_usb_connector_driver);
+	if (ret) {
+		spi_unregister_driver(&stm_ipc_driver);
+		return ret;
+	}
+
+	return 0;
+}
+static void __exit stm_ipc_exit(void)
+{
+	spi_unregister_driver(&stm_ipc_driver);
+	platform_driver_unregister(&stm_usb_connector_driver);
+}
+
+module_init(stm_ipc_init);
+module_exit(stm_ipc_exit);
+
+MODULE_AUTHOR("Samuel Morris <scmorris.dev@gmail.com>");
+MODULE_DESCRIPTION("STM32 SPI IPC and virtual Extcon Driver");
+MODULE_LICENSE("GPL v2");

From 6fc6a6fc62597eb259eccbb828a861726d22d500 Mon Sep 17 00:00:00 2001
From: Samuel Morris <scmorris.dev@gmail.com>
Date: Mon, 1 Jun 2026 14:32:29 -0700
Subject: [PATCH 02/22] arm64: configs: Enable STM32 SPI IPC extcon driver

Enable CONFIG_EXTCON_STM32_SPI_IPC in mt_connect_defconfig to compile
the custom stm-spi-ipc extcon driver directly into the kernel.
---
 arch/arm64/configs/mt_connect_defconfig | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/arm64/configs/mt_connect_defconfig b/arch/arm64/configs/mt_connect_defconfig
index dd15ba66e2408..31e80d4eeb68d 100644
--- a/arch/arm64/configs/mt_connect_defconfig
+++ b/arch/arm64/configs/mt_connect_defconfig
@@ -654,6 +654,7 @@ CONFIG_FSL_QIXIS=y
 CONFIG_SOC_TI=y
 CONFIG_EXTCON_PTN5150=m
 CONFIG_EXTCON_USB_GPIO=y
+CONFIG_EXTCON_STM32_SPI_IPC=y
 CONFIG_IIO=y
 CONFIG_FXLS8962AF_I2C=m
 CONFIG_IIO_ST_ACCEL_3AXIS=m

From 579eca85d33f31287963ac15b3416d2ec931eb0f Mon Sep 17 00:00:00 2001
From: Samuel Morris <scmorris.dev@gmail.com>
Date: Mon, 1 Jun 2026 14:32:39 -0700
Subject: [PATCH 03/22] arm64: dts: freescale: Add STM32 SPI IPC and extcon
 nodes

Configure the ECSPI2 controller on mt-connect to support the STM32 SPI
IPC slave node and its virtual USB connector child nodes. Bind
&usbotg1 and &usbotg2 to their respective virtual extcon connectors
and enable role switching. Set up pin control and active-low interrupt
for GPIO2_IO11.
---
 arch/arm64/boot/dts/freescale/mt-connect.dts | 28 +++++++++++++++-----
 1 file changed, 22 insertions(+), 6 deletions(-)

diff --git a/arch/arm64/boot/dts/freescale/mt-connect.dts b/arch/arm64/boot/dts/freescale/mt-connect.dts
index 49b02c88cba9d..949475cda4227 100644
--- a/arch/arm64/boot/dts/freescale/mt-connect.dts
+++ b/arch/arm64/boot/dts/freescale/mt-connect.dts
@@ -495,15 +495,29 @@
 };
 
 &ecspi2 {
-	status = "okay";
+	#address-cells = <1>;
+	#size-cells = <0>;
 	pinctrl-names = "default";
-	pinctrl-0 = <&pinctrl_ecspi2>;
+	pinctrl-0 = <&pinctrl_ecspi2 &pinctrl_stm_ipc>;
 	cs-gpios = <&gpio5 13 GPIO_ACTIVE_LOW>;
+	status = "okay";
 
-	spidev1: spi@0 {
+	stm_ipc: stm32-ipc@0 {
+		compatible = "multitracks,stm32-spi-ipc";
 		reg = <0>;
-		compatible = "rohm,dh2228fv";
-		spi-max-frequency = <500000>;
+		spi-max-frequency = <10000000>;
+		interrupt-parent = <&gpio2>;
+		interrupts = <11 IRQ_TYPE_EDGE_FALLING>;
+
+		usb1_connector: connector-usb1 {
+			compatible = "multitracks,stm32-usb-connector";
+			port-id = <0>;
+		};
+
+		usb2_connector: connector-usb2 {
+			compatible = "multitracks,stm32-usb-connector";
+			port-id = <1>;
+		};
 	};
 };
 
@@ -520,6 +534,7 @@
 };
 
 &usbotg1 {
+	extcon = <&usb1_connector>;
 	hnp-disable;
 	srp-disable;
 	adp-disable;
@@ -533,6 +548,7 @@
 };
 
 &usbotg2 {
+	extcon = <&usb2_connector>;
 	hnp-disable;
 	srp-disable;
 	adp-disable;
@@ -710,7 +726,7 @@
 		>;
 	};
 
-	pinctrl_typec1: typec1grp {
+	pinctrl_stm_ipc: stmipcgrp {
 		fsl,pins = <
 		MX8MM_IOMUXC_SD1_STROBE_GPIO2_IO11			0x159
 		>;

From ba8eea041b21c24d99d454bafffa207adf5c12cf Mon Sep 17 00:00:00 2001
From: Samuel Morris <scmorris.dev@gmail.com>
Date: Wed, 3 Jun 2026 15:34:42 -0700
Subject: [PATCH 04/22] extcon: Kconfig: select CRC8 and improve stm32-ipc help
 description

---
 drivers/extcon/Kconfig | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/extcon/Kconfig b/drivers/extcon/Kconfig
index 8852425b68fba..910f1eb15b121 100644
--- a/drivers/extcon/Kconfig
+++ b/drivers/extcon/Kconfig
@@ -179,9 +179,11 @@ config EXTCON_USB_GPIO
 config EXTCON_STM32_SPI_IPC
 	tristate "STM32 SPI IPC and Virtual Extcon support"
 	depends on SPI
+	select CRC8
 	help
-	  Say Y here to enable the STM32 to i.MX8MM SPI IPC and Virtual Extcon
-	  driver, which handles USB connection/cable event notifications over SPI.
+	  Say Y here to enable the STM32 SPI IPC and Virtual Extcon driver,
+	  which handles USB connection/cable event notifications reported
+	  by an external STM32 co-processor over SPI.
 
 config EXTCON_USBC_CROS_EC
 	tristate "ChromeOS Embedded Controller EXTCON support"

From 2cedf5cbd3f99433300a88e4f090209ce4ec9c47 Mon Sep 17 00:00:00 2001
From: Samuel Morris <scmorris.dev@gmail.com>
Date: Wed, 3 Jun 2026 15:35:26 -0700
Subject: [PATCH 05/22] extcon: stm32-ipc: remove unused GPIO header

---
 drivers/extcon/extcon-stm32-ipc.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/drivers/extcon/extcon-stm32-ipc.c b/drivers/extcon/extcon-stm32-ipc.c
index ad70407cbb0c7..f899d5824230e 100644
--- a/drivers/extcon/extcon-stm32-ipc.c
+++ b/drivers/extcon/extcon-stm32-ipc.c
@@ -9,7 +9,6 @@
 #include <linux/spi/spi.h>
 #include <linux/extcon-provider.h>
 #include <linux/interrupt.h>
-#include <linux/gpio/consumer.h>
 #include <linux/platform_device.h>
 #include <linux/of_platform.h>
 #include <linux/slab.h>

From 7ee736b38c2ca202e76425bc997fcdffdd4aa03b Mon Sep 17 00:00:00 2001
From: Samuel Morris <scmorris.dev@gmail.com>
Date: Wed, 3 Jun 2026 15:35:27 -0700
Subject: [PATCH 06/22] extcon: stm32-ipc: fallback to safe disconnected state
 error

---
 drivers/extcon/extcon-stm32-ipc.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/extcon/extcon-stm32-ipc.c b/drivers/extcon/extcon-stm32-ipc.c
index f899d5824230e..8df0c09fee12c 100644
--- a/drivers/extcon/extcon-stm32-ipc.c
+++ b/drivers/extcon/extcon-stm32-ipc.c
@@ -66,6 +66,10 @@ static void stm_ipc_update_state(struct extcon_dev *edev, u8 state)
 		extcon_set_state_sync(edev, EXTCON_USB_HOST, true);
 		break;
 	default:
+		/* Fallback to safe disconnected state on protocol error */
+		extcon_set_state_sync(edev, EXTCON_USB, false);
+		extcon_set_state_sync(edev, EXTCON_USB_HOST, false);
+		pr_warn_ratelimited("stm-spi-ipc: Invalid USB connector state: %u\n", state);
 		break;
 	}
 }

From d24f351c8c1805af88d90efb7d58ecf5b69d7df2 Mon Sep 17 00:00:00 2001
From: Samuel Morris <scmorris.dev@gmail.com>
Date: Wed, 3 Jun 2026 15:35:27 -0700
Subject: [PATCH 07/22] extcon: stm32-ipc: Use dev_dbg in threaded IRQ to avoid
 log flooding

---
 drivers/extcon/extcon-stm32-ipc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/extcon/extcon-stm32-ipc.c b/drivers/extcon/extcon-stm32-ipc.c
index 8df0c09fee12c..01c31f82d84a7 100644
--- a/drivers/extcon/extcon-stm32-ipc.c
+++ b/drivers/extcon/extcon-stm32-ipc.c
@@ -123,7 +123,7 @@ static irqreturn_t stm_ipc_threaded_irq(int irq, void *dev_id)
 	if (rx_buf.type == MSG_TYPE_USB_EVENT) {
 		u8 port_info[2] = { rx_buf.port, rx_buf.state };
 
-		dev_info(&priv->spi->dev, "USB Event from STM32 on Port %d: State %d\n", rx_buf.port, rx_buf.state);
+		dev_dbg(&priv->spi->dev, "USB Event from STM32 on Port %d: State %d\n", rx_buf.port, rx_buf.state);
 		device_for_each_child(&priv->spi->dev, port_info, match_and_update_state);
 	}
 

From 97c4e671a68c668c8b630d26371759f5df623c6d Mon Sep 17 00:00:00 2001
From: Samuel Morris <scmorris.dev@gmail.com>
Date: Wed, 3 Jun 2026 15:35:27 -0700
Subject: [PATCH 08/22] extcon: stm32-ipc: create per-device debugfs to avoid
 collisions

---
 drivers/extcon/extcon-stm32-ipc.c | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/drivers/extcon/extcon-stm32-ipc.c b/drivers/extcon/extcon-stm32-ipc.c
index 01c31f82d84a7..6366d3a85dde9 100644
--- a/drivers/extcon/extcon-stm32-ipc.c
+++ b/drivers/extcon/extcon-stm32-ipc.c
@@ -214,8 +214,20 @@ static int stm_ipc_probe(struct spi_device *spi)
 	mutex_init(&priv->lock);
 	spi_set_drvdata(spi, priv);
 
-	/* Initialize DebugFS root directory under /sys/kernel/debug/stm_ipc */
-	priv->debugfs_root = debugfs_create_dir("stm_ipc", NULL);
+	struct dentry *parent;
+
+	/* Initialize DebugFS subdirectory under /sys/kernel/debug/stm_ipc/<device> */
+	parent = debugfs_create_dir("stm_ipc", NULL);
+	if (IS_ERR_OR_NULL(parent)) {
+		dev_warn(&spi->dev, "Failed to create debugfs parent directory\n");
+		priv->debugfs_root = NULL;
+	} else {
+		priv->debugfs_root = debugfs_create_dir(dev_name(&spi->dev), parent);
+		if (IS_ERR_OR_NULL(priv->debugfs_root)) {
+			dev_warn(&spi->dev, "Failed to create debugfs root directory\n");
+			priv->debugfs_root = NULL;
+		}
+	}
 
 	/* Populate subnodes as platform devices (this probes the connector sub-drivers) */
 	ret = devm_of_platform_populate(&spi->dev);

From 2398ab9a5143f1261172497f99d862404318dc22 Mon Sep 17 00:00:00 2001
From: Samuel Morris <scmorris.dev@gmail.com>
Date: Wed, 3 Jun 2026 15:35:27 -0700
Subject: [PATCH 09/22] extcon: stm32-ipc: implement CRC-8/length validation on
 SPI packets

---
 drivers/extcon/extcon-stm32-ipc.c | 24 +++++++++++++++++++++++-
 1 file changed, 23 insertions(+), 1 deletion(-)

diff --git a/drivers/extcon/extcon-stm32-ipc.c b/drivers/extcon/extcon-stm32-ipc.c
index 6366d3a85dde9..2ba47f957db1b 100644
--- a/drivers/extcon/extcon-stm32-ipc.c
+++ b/drivers/extcon/extcon-stm32-ipc.c
@@ -14,6 +14,7 @@
 #include <linux/slab.h>
 #include <linux/debugfs.h>
 #include <linux/mutex.h>
+#include <linux/crc8.h>
 
 #define DRIVER_NAME "stm-spi-ipc"
 
@@ -31,6 +32,8 @@ struct stm_ipc_packet {
 } __packed;
 
 /* Parent SPI controller private structure */
+DECLARE_CRC8_TABLE(stm_crc8_table);
+
 struct stm_ipc_priv {
 	struct spi_device *spi;
 	struct mutex lock;
@@ -102,6 +105,7 @@ static irqreturn_t stm_ipc_threaded_irq(int irq, void *dev_id)
 	};
 	struct spi_message m;
 	int ret;
+	u8 calc_crc;
 
 	mutex_lock(&priv->lock);
 
@@ -113,12 +117,27 @@ static irqreturn_t stm_ipc_threaded_irq(int irq, void *dev_id)
 		goto out;
 	}
 
-	/* Validate packet */
+	/* Validate magic byte */
 	if (rx_buf.magic != STM_IPC_MSG_MAGIC) {
 		dev_warn_ratelimited(&priv->spi->dev, "Invalid magic byte: 0x%02x\n", rx_buf.magic);
 		goto out;
 	}
 
+	/* Validate packet CRC */
+	calc_crc = crc8(stm_crc8_table, (const u8 *)&rx_buf, offsetof(struct stm_ipc_packet, crc), 0);
+	if (calc_crc != rx_buf.crc) {
+		dev_warn_ratelimited(&priv->spi->dev, "CRC mismatch: read 0x%02x, calculated 0x%02x\n",
+				     rx_buf.crc, calc_crc);
+		goto out;
+	}
+
+	/* Validate packet payload length for USB events */
+	if (rx_buf.type == MSG_TYPE_USB_EVENT && rx_buf.length != 2) {
+		dev_warn_ratelimited(&priv->spi->dev, "Invalid packet length: %u (expected 2)\n",
+				     rx_buf.length);
+		goto out;
+	}
+
 	/* Process USB event */
 	if (rx_buf.type == MSG_TYPE_USB_EVENT) {
 		u8 port_info[2] = { rx_buf.port, rx_buf.state };
@@ -216,6 +235,9 @@ static int stm_ipc_probe(struct spi_device *spi)
 
 	struct dentry *parent;
 
+	/* Setup CRC8 lookup table (polynomial 0x07) */
+	crc8_populate_msb(stm_crc8_table, 0x07);
+
 	/* Initialize DebugFS subdirectory under /sys/kernel/debug/stm_ipc/<device> */
 	parent = debugfs_create_dir("stm_ipc", NULL);
 	if (IS_ERR_OR_NULL(parent)) {

From 813a8668e4210c7fd45abed96ff144ead3e7045b Mon Sep 17 00:00:00 2001
From: Samuel Morris <scmorris.dev@gmail.com>
Date: Wed, 3 Jun 2026 15:51:19 -0700
Subject: [PATCH 10/22] extcon: stm32-ipc: replace magic numbers with enum and
 defines

---
 drivers/extcon/extcon-stm32-ipc.c | 30 +++++++++++++++++++-----------
 1 file changed, 19 insertions(+), 11 deletions(-)

diff --git a/drivers/extcon/extcon-stm32-ipc.c b/drivers/extcon/extcon-stm32-ipc.c
index 2ba47f957db1b..79298b811fad3 100644
--- a/drivers/extcon/extcon-stm32-ipc.c
+++ b/drivers/extcon/extcon-stm32-ipc.c
@@ -19,15 +19,23 @@
 #define DRIVER_NAME "stm-spi-ipc"
 
 /* Protocol constants */
-#define STM_IPC_MSG_MAGIC   0x5A
-#define MSG_TYPE_USB_EVENT  0x01
+#define STM_IPC_MSG_MAGIC         0x5A
+#define MSG_TYPE_USB_EVENT        0x01
+#define STM_IPC_MSG_LEN_USB_EVENT 2
+#define STM_IPC_CRC8_POLYNOMIAL   0x07
+
+enum stm_ipc_usb_state {
+	STM_IPC_USB_STATE_DISCONNECTED = 0,
+	STM_IPC_USB_STATE_PERIPHERAL   = 1,
+	STM_IPC_USB_STATE_HOST         = 2,
+};
 
 struct stm_ipc_packet {
 	u8 magic;
 	u8 type;
 	u8 length;
 	u8 port;
-	u8 state; /* 0 = disconnected, 1 = peripheral (VBUS), 2 = host (ID) */
+	u8 state; /* enum stm_ipc_usb_state */
 	u8 crc;
 } __packed;
 
@@ -56,15 +64,15 @@ static const unsigned int stm_usb_cable[] = {
 static void stm_ipc_update_state(struct extcon_dev *edev, u8 state)
 {
 	switch (state) {
-	case 0: /* Disconnected */
+	case STM_IPC_USB_STATE_DISCONNECTED:
 		extcon_set_state_sync(edev, EXTCON_USB, false);
 		extcon_set_state_sync(edev, EXTCON_USB_HOST, false);
 		break;
-	case 1: /* Peripheral Mode (VBUS present) */
+	case STM_IPC_USB_STATE_PERIPHERAL:
 		extcon_set_state_sync(edev, EXTCON_USB_HOST, false);
 		extcon_set_state_sync(edev, EXTCON_USB, true);
 		break;
-	case 2: /* Host Mode (ID ground) */
+	case STM_IPC_USB_STATE_HOST:
 		extcon_set_state_sync(edev, EXTCON_USB, false);
 		extcon_set_state_sync(edev, EXTCON_USB_HOST, true);
 		break;
@@ -132,9 +140,9 @@ static irqreturn_t stm_ipc_threaded_irq(int irq, void *dev_id)
 	}
 
 	/* Validate packet payload length for USB events */
-	if (rx_buf.type == MSG_TYPE_USB_EVENT && rx_buf.length != 2) {
-		dev_warn_ratelimited(&priv->spi->dev, "Invalid packet length: %u (expected 2)\n",
-				     rx_buf.length);
+	if (rx_buf.type == MSG_TYPE_USB_EVENT && rx_buf.length != STM_IPC_MSG_LEN_USB_EVENT) {
+		dev_warn_ratelimited(&priv->spi->dev, "Invalid packet length: %u (expected %d)\n",
+				     rx_buf.length, STM_IPC_MSG_LEN_USB_EVENT);
 		goto out;
 	}
 
@@ -156,7 +164,7 @@ static int stm_ipc_sim_write(void *data, u64 val)
 {
 	struct stm_connector_priv *priv = data;
 
-	if (val > 2)
+	if (val > STM_IPC_USB_STATE_HOST)
 		return -EINVAL;
 
 	stm_ipc_update_state(priv->edev, (u8)val);
@@ -236,7 +244,7 @@ static int stm_ipc_probe(struct spi_device *spi)
 	struct dentry *parent;
 
 	/* Setup CRC8 lookup table (polynomial 0x07) */
-	crc8_populate_msb(stm_crc8_table, 0x07);
+	crc8_populate_msb(stm_crc8_table, STM_IPC_CRC8_POLYNOMIAL);
 
 	/* Initialize DebugFS subdirectory under /sys/kernel/debug/stm_ipc/<device> */
 	parent = debugfs_create_dir("stm_ipc", NULL);

From fa00235fa0d390a6bebed01b39ede8622d79c6dc Mon Sep 17 00:00:00 2001
From: Overdr0ne <scmorris.dev@gmail.com>
Date: Wed, 8 Jul 2026 17:43:03 -0600
Subject: [PATCH 11/22] extcon: stm32-ipc: add Kconfig dependency on OF

Add a dependency on CONFIG_OF for CONFIG_EXTCON_STM32_SPI_IPC to
prevent compile/configuration failures on architectures where Device
Tree is not supported.
---
 drivers/extcon/Kconfig | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/extcon/Kconfig b/drivers/extcon/Kconfig
index 910f1eb15b121..2681b3465c1b1 100644
--- a/drivers/extcon/Kconfig
+++ b/drivers/extcon/Kconfig
@@ -178,7 +178,7 @@ config EXTCON_USB_GPIO
 
 config EXTCON_STM32_SPI_IPC
 	tristate "STM32 SPI IPC and Virtual Extcon support"
-	depends on SPI
+	depends on SPI && OF
 	select CRC8
 	help
 	  Say Y here to enable the STM32 SPI IPC and Virtual Extcon driver,

From a76fffd64042f41c6d204a3c37430627929944f1 Mon Sep 17 00:00:00 2001
From: Overdr0ne <scmorris.dev@gmail.com>
Date: Wed, 8 Jul 2026 17:43:17 -0600
Subject: [PATCH 12/22] extcon: stm32-ipc: fix declarations after statements

Move variable declarations in stm_usb_connector_probe() and
stm_ipc_probe() to the top of functions. This resolves compilation
failures under -Wdeclaration-after-statement.
---
 drivers/extcon/extcon-stm32-ipc.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/extcon/extcon-stm32-ipc.c b/drivers/extcon/extcon-stm32-ipc.c
index 79298b811fad3..baea9ef6ca7c1 100644
--- a/drivers/extcon/extcon-stm32-ipc.c
+++ b/drivers/extcon/extcon-stm32-ipc.c
@@ -177,6 +177,8 @@ static int stm_usb_connector_probe(struct platform_device *pdev)
 {
 	struct device *dev = &pdev->dev;
 	struct stm_connector_priv *priv;
+	struct stm_ipc_priv *parent_priv;
+	char name[32];
 	int ret;
 
 	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
@@ -202,9 +204,8 @@ static int stm_usb_connector_probe(struct platform_device *pdev)
 	platform_set_drvdata(pdev, priv);
 
 	/* Set up DebugFS for this virtual connector for runtime simulation */
-	struct stm_ipc_priv *parent_priv = dev_get_drvdata(dev->parent);
+	parent_priv = dev_get_drvdata(dev->parent);
 	if (parent_priv && parent_priv->debugfs_root) {
-		char name[32];
 		snprintf(name, sizeof(name), "usb%d_sim", priv->port_id + 1);
 		debugfs_create_file(name, 0200, parent_priv->debugfs_root, priv, &stm_ipc_sim_fops);
 	}
@@ -231,6 +232,7 @@ static struct platform_driver stm_usb_connector_driver = {
 static int stm_ipc_probe(struct spi_device *spi)
 {
 	struct stm_ipc_priv *priv;
+	struct dentry *parent;
 	int ret;
 
 	priv = devm_kzalloc(&spi->dev, sizeof(*priv), GFP_KERNEL);
@@ -241,8 +243,6 @@ static int stm_ipc_probe(struct spi_device *spi)
 	mutex_init(&priv->lock);
 	spi_set_drvdata(spi, priv);
 
-	struct dentry *parent;
-
 	/* Setup CRC8 lookup table (polynomial 0x07) */
 	crc8_populate_msb(stm_crc8_table, STM_IPC_CRC8_POLYNOMIAL);
 

From 4033d4280efe7eef121faa63c36f7cb05ae359b5 Mon Sep 17 00:00:00 2001
From: Overdr0ne <scmorris.dev@gmail.com>
Date: Wed, 8 Jul 2026 17:43:23 -0600
Subject: [PATCH 13/22] extcon: stm32-ipc: validate port-id DT property

Validate the 'port-id' Device Tree property in stm_usb_connector_probe()
to ensure it fits within [0, 255] before casting it to u8. Avoids silently
ignoring out-of-bounds inputs from the device tree.
---
 drivers/extcon/extcon-stm32-ipc.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/extcon/extcon-stm32-ipc.c b/drivers/extcon/extcon-stm32-ipc.c
index baea9ef6ca7c1..2593374184af0 100644
--- a/drivers/extcon/extcon-stm32-ipc.c
+++ b/drivers/extcon/extcon-stm32-ipc.c
@@ -51,7 +51,7 @@ struct stm_ipc_priv {
 /* Child connector platform device private structure */
 struct stm_connector_priv {
 	struct extcon_dev *edev;
-	u32 port_id;
+	u8 port_id;
 };
 
 static const unsigned int stm_usb_cable[] = {
@@ -179,17 +179,23 @@ static int stm_usb_connector_probe(struct platform_device *pdev)
 	struct stm_connector_priv *priv;
 	struct stm_ipc_priv *parent_priv;
 	char name[32];
+	u32 val;
 	int ret;
 
 	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
 	if (!priv)
 		return -ENOMEM;
 
-	ret = of_property_read_u32(dev->of_node, "port-id", &priv->port_id);
+	ret = of_property_read_u32(dev->of_node, "port-id", &val);
 	if (ret) {
 		dev_err(dev, "Missing 'port-id' property\n");
 		return ret;
 	}
+	if (val > 255) {
+		dev_err(dev, "Invalid 'port-id' value: %u (must be <= 255)\n", val);
+		return -EINVAL;
+	}
+	priv->port_id = (u8)val;
 
 	priv->edev = devm_extcon_dev_allocate(dev, stm_usb_cable);
 	if (IS_ERR(priv->edev))

From a18f363607f091fe5e4ed4a0dc8e69658ae01f8c Mon Sep 17 00:00:00 2001
From: Overdr0ne <scmorris.dev@gmail.com>
Date: Wed, 8 Jul 2026 17:43:30 -0600
Subject: [PATCH 14/22] extcon: stm32-ipc: use dev_warn_ratelimited

Replace pr_warn_ratelimited() with dev_warn_ratelimited(&edev->dev, ...)
in stm_ipc_update_state(). This logs the warning in the context of the
specific extcon device instance, making debugging easier.
---
 drivers/extcon/extcon-stm32-ipc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/extcon/extcon-stm32-ipc.c b/drivers/extcon/extcon-stm32-ipc.c
index 2593374184af0..c1706d5379c8f 100644
--- a/drivers/extcon/extcon-stm32-ipc.c
+++ b/drivers/extcon/extcon-stm32-ipc.c
@@ -80,7 +80,7 @@ static void stm_ipc_update_state(struct extcon_dev *edev, u8 state)
 		/* Fallback to safe disconnected state on protocol error */
 		extcon_set_state_sync(edev, EXTCON_USB, false);
 		extcon_set_state_sync(edev, EXTCON_USB_HOST, false);
-		pr_warn_ratelimited("stm-spi-ipc: Invalid USB connector state: %u\n", state);
+		dev_warn_ratelimited(&edev->dev, "Invalid USB connector state: %u\n", state);
 		break;
 	}
 }

From af221468bd7dcee6fd574c1ae1eba8674c9dafc6 Mon Sep 17 00:00:00 2001
From: Overdr0ne <scmorris.dev@gmail.com>
Date: Wed, 8 Jul 2026 17:43:37 -0600
Subject: [PATCH 15/22] extcon: stm32-ipc: initialize CRC-8 table once

Move crc8_populate_msb() from stm_ipc_probe() to stm_ipc_init().
Populating the table during module initialization instead of probe prevents
a concurrent write race condition when multiple devices are probed.
---
 drivers/extcon/extcon-stm32-ipc.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/extcon/extcon-stm32-ipc.c b/drivers/extcon/extcon-stm32-ipc.c
index c1706d5379c8f..713b35a566028 100644
--- a/drivers/extcon/extcon-stm32-ipc.c
+++ b/drivers/extcon/extcon-stm32-ipc.c
@@ -249,8 +249,7 @@ static int stm_ipc_probe(struct spi_device *spi)
 	mutex_init(&priv->lock);
 	spi_set_drvdata(spi, priv);
 
-	/* Setup CRC8 lookup table (polynomial 0x07) */
-	crc8_populate_msb(stm_crc8_table, STM_IPC_CRC8_POLYNOMIAL);
+
 
 	/* Initialize DebugFS subdirectory under /sys/kernel/debug/stm_ipc/<device> */
 	parent = debugfs_create_dir("stm_ipc", NULL);
@@ -317,6 +316,9 @@ static int __init stm_ipc_init(void)
 {
 	int ret;
 
+	/* Setup CRC8 lookup table (polynomial 0x07) once */
+	crc8_populate_msb(stm_crc8_table, STM_IPC_CRC8_POLYNOMIAL);
+
 	ret = spi_register_driver(&stm_ipc_driver);
 	if (ret)
 		return ret;

From 7db84be700f91ebea477be9d177a8fea3e2fad1d Mon Sep 17 00:00:00 2001
From: Overdr0ne <scmorris.dev@gmail.com>
Date: Wed, 8 Jul 2026 17:43:44 -0600
Subject: [PATCH 16/22] extcon: stm32-ipc: fix debugfs lifetime management

Create the top-level 'stm_ipc' debugfs parent directory once globally
during module initialization and remove it during module exit.
Per-device debugfs subdirectories are created under this parent directory during probe.
---
 drivers/extcon/extcon-stm32-ipc.c | 26 +++++++++++++++++---------
 1 file changed, 17 insertions(+), 9 deletions(-)

diff --git a/drivers/extcon/extcon-stm32-ipc.c b/drivers/extcon/extcon-stm32-ipc.c
index 713b35a566028..c8e060f63a89b 100644
--- a/drivers/extcon/extcon-stm32-ipc.c
+++ b/drivers/extcon/extcon-stm32-ipc.c
@@ -41,6 +41,7 @@ struct stm_ipc_packet {
 
 /* Parent SPI controller private structure */
 DECLARE_CRC8_TABLE(stm_crc8_table);
+static struct dentry *stm_ipc_debugfs_dir;
 
 struct stm_ipc_priv {
 	struct spi_device *spi;
@@ -238,7 +239,6 @@ static struct platform_driver stm_usb_connector_driver = {
 static int stm_ipc_probe(struct spi_device *spi)
 {
 	struct stm_ipc_priv *priv;
-	struct dentry *parent;
 	int ret;
 
 	priv = devm_kzalloc(&spi->dev, sizeof(*priv), GFP_KERNEL);
@@ -252,16 +252,14 @@ static int stm_ipc_probe(struct spi_device *spi)
 
 
 	/* Initialize DebugFS subdirectory under /sys/kernel/debug/stm_ipc/<device> */
-	parent = debugfs_create_dir("stm_ipc", NULL);
-	if (IS_ERR_OR_NULL(parent)) {
-		dev_warn(&spi->dev, "Failed to create debugfs parent directory\n");
-		priv->debugfs_root = NULL;
-	} else {
-		priv->debugfs_root = debugfs_create_dir(dev_name(&spi->dev), parent);
+	if (stm_ipc_debugfs_dir) {
+		priv->debugfs_root = debugfs_create_dir(dev_name(&spi->dev), stm_ipc_debugfs_dir);
 		if (IS_ERR_OR_NULL(priv->debugfs_root)) {
 			dev_warn(&spi->dev, "Failed to create debugfs root directory\n");
 			priv->debugfs_root = NULL;
 		}
+	} else {
+		priv->debugfs_root = NULL;
 	}
 
 	/* Populate subnodes as platform devices (this probes the connector sub-drivers) */
@@ -319,22 +317,32 @@ static int __init stm_ipc_init(void)
 	/* Setup CRC8 lookup table (polynomial 0x07) once */
 	crc8_populate_msb(stm_crc8_table, STM_IPC_CRC8_POLYNOMIAL);
 
+	/* Setup global debugfs parent directory */
+	stm_ipc_debugfs_dir = debugfs_create_dir("stm_ipc", NULL);
+	if (IS_ERR_OR_NULL(stm_ipc_debugfs_dir))
+		stm_ipc_debugfs_dir = NULL;
+
 	ret = spi_register_driver(&stm_ipc_driver);
 	if (ret)
-		return ret;
+		goto err_debugfs;
 
 	ret = platform_driver_register(&stm_usb_connector_driver);
 	if (ret) {
 		spi_unregister_driver(&stm_ipc_driver);
-		return ret;
+		goto err_debugfs;
 	}
 
 	return 0;
+
+err_debugfs:
+	debugfs_remove_recursive(stm_ipc_debugfs_dir);
+	return ret;
 }
 static void __exit stm_ipc_exit(void)
 {
 	spi_unregister_driver(&stm_ipc_driver);
 	platform_driver_unregister(&stm_usb_connector_driver);
+	debugfs_remove_recursive(stm_ipc_debugfs_dir);
 }
 
 module_init(stm_ipc_init);

From 57f6c94ad87bd03f2779056b8771403f7954fde3 Mon Sep 17 00:00:00 2001
From: Overdr0ne <scmorris.dev@gmail.com>
Date: Wed, 8 Jul 2026 18:14:53 -0600
Subject: [PATCH 17/22] extcon: stm32-ipc: cache states to reduce churn

Read the current cable states of EXTCON_USB and EXTCON_USB_HOST
first in stm_ipc_update_state(). Only invoke extcon_set_state_sync() when
a state bit actually changes, clearing the opposite state first. This avoids
unnecessary extcon uevent updates and userspace churn.
---
 drivers/extcon/extcon-stm32-ipc.c | 39 ++++++++++++++++++++++++-------
 1 file changed, 31 insertions(+), 8 deletions(-)

diff --git a/drivers/extcon/extcon-stm32-ipc.c b/drivers/extcon/extcon-stm32-ipc.c
index c8e060f63a89b..f40874a60f3ab 100644
--- a/drivers/extcon/extcon-stm32-ipc.c
+++ b/drivers/extcon/extcon-stm32-ipc.c
@@ -64,26 +64,49 @@ static const unsigned int stm_usb_cable[] = {
 /* Helper to update extcon state based on STM32 reporting */
 static void stm_ipc_update_state(struct extcon_dev *edev, u8 state)
 {
+	int usb_state = extcon_get_state(edev, EXTCON_USB);
+	int host_state = extcon_get_state(edev, EXTCON_USB_HOST);
+	bool want_usb = false;
+	bool want_host = false;
+
+	if (usb_state < 0 || host_state < 0) {
+		dev_err_ratelimited(&edev->dev, "Failed to get current extcon state\n");
+		return;
+	}
+
 	switch (state) {
 	case STM_IPC_USB_STATE_DISCONNECTED:
-		extcon_set_state_sync(edev, EXTCON_USB, false);
-		extcon_set_state_sync(edev, EXTCON_USB_HOST, false);
+		want_usb = false;
+		want_host = false;
 		break;
 	case STM_IPC_USB_STATE_PERIPHERAL:
-		extcon_set_state_sync(edev, EXTCON_USB_HOST, false);
-		extcon_set_state_sync(edev, EXTCON_USB, true);
+		want_usb = true;
+		want_host = false;
 		break;
 	case STM_IPC_USB_STATE_HOST:
-		extcon_set_state_sync(edev, EXTCON_USB, false);
-		extcon_set_state_sync(edev, EXTCON_USB_HOST, true);
+		want_usb = false;
+		want_host = true;
 		break;
 	default:
 		/* Fallback to safe disconnected state on protocol error */
-		extcon_set_state_sync(edev, EXTCON_USB, false);
-		extcon_set_state_sync(edev, EXTCON_USB_HOST, false);
+		want_usb = false;
+		want_host = false;
 		dev_warn_ratelimited(&edev->dev, "Invalid USB connector state: %u\n", state);
 		break;
 	}
+
+	/* Only update states if they have actually changed, clearing opposite first */
+	if (want_usb != usb_state || want_host != host_state) {
+		if (!want_usb && usb_state)
+			extcon_set_state_sync(edev, EXTCON_USB, false);
+		if (!want_host && host_state)
+			extcon_set_state_sync(edev, EXTCON_USB_HOST, false);
+
+		if (want_usb && !usb_state)
+			extcon_set_state_sync(edev, EXTCON_USB, true);
+		if (want_host && !host_state)
+			extcon_set_state_sync(edev, EXTCON_USB_HOST, true);
+	}
 }
 
 /* Callback used to find and update state of correct child platform device */

From 9d2588b0ee1efcc0f2937675dae23137b988b489 Mon Sep 17 00:00:00 2001
From: Overdr0ne <scmorris.dev@gmail.com>
Date: Wed, 8 Jul 2026 18:14:59 -0600
Subject: [PATCH 18/22] extcon: stm32-ipc: rate-limit SPI transfer error logs

Replace dev_err() with dev_err_ratelimited() on SPI sync transfer
failures in stm_ipc_threaded_irq(). This avoids flooding the kernel
log in case the SPI bus becomes misconfigured or experiences noise.
---
 drivers/extcon/extcon-stm32-ipc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/extcon/extcon-stm32-ipc.c b/drivers/extcon/extcon-stm32-ipc.c
index f40874a60f3ab..36d46d8431967 100644
--- a/drivers/extcon/extcon-stm32-ipc.c
+++ b/drivers/extcon/extcon-stm32-ipc.c
@@ -145,7 +145,7 @@ static irqreturn_t stm_ipc_threaded_irq(int irq, void *dev_id)
 	spi_message_add_tail(&t, &m);
 	ret = spi_sync(priv->spi, &m);
 	if (ret < 0) {
-		dev_err(&priv->spi->dev, "SPI sync transfer failed: %d\n", ret);
+		dev_err_ratelimited(&priv->spi->dev, "SPI sync transfer failed: %d\n", ret);
 		goto out;
 	}
 

From 39b5db701840241cc397c54bff20179a2045c72b Mon Sep 17 00:00:00 2001
From: Overdr0ne <scmorris.dev@gmail.com>
Date: Wed, 8 Jul 2026 18:15:05 -0600
Subject: [PATCH 19/22] extcon: stm32-ipc: warn on unmatched connector ports

Check the return value of device_for_each_child() when dispatching
USB events. If no child platform connector matches the reported port ID,
emit a rate-limited warning log to assist in troubleshooting Device Tree
or protocol mismatches.
---
 drivers/extcon/extcon-stm32-ipc.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/extcon/extcon-stm32-ipc.c b/drivers/extcon/extcon-stm32-ipc.c
index 36d46d8431967..59a066b367ffc 100644
--- a/drivers/extcon/extcon-stm32-ipc.c
+++ b/drivers/extcon/extcon-stm32-ipc.c
@@ -175,7 +175,10 @@ static irqreturn_t stm_ipc_threaded_irq(int irq, void *dev_id)
 		u8 port_info[2] = { rx_buf.port, rx_buf.state };
 
 		dev_dbg(&priv->spi->dev, "USB Event from STM32 on Port %d: State %d\n", rx_buf.port, rx_buf.state);
-		device_for_each_child(&priv->spi->dev, port_info, match_and_update_state);
+		ret = device_for_each_child(&priv->spi->dev, port_info, match_and_update_state);
+		if (ret == 0) {
+			dev_warn_ratelimited(&priv->spi->dev, "No matching USB connector found for Port %d\n", rx_buf.port);
+		}
 	}
 
 out:

From f61e32cd3f20d8d57db9336b0d57eb9f36d0a311 Mon Sep 17 00:00:00 2001
From: Overdr0ne <scmorris.dev@gmail.com>
Date: Wed, 8 Jul 2026 18:15:12 -0600
Subject: [PATCH 20/22] extcon: stm32-ipc: clean up debugfs to avoid UAF

Register a devm device cleanup action in stm_usb_connector_probe()
to automatically call debugfs_remove() on the connector's simulation
file when the connector device is unbound. This prevents a potential
use-after-free (UAF) if userspace interacts with the simulation file after
the device is unbound.
---
 drivers/extcon/extcon-stm32-ipc.c | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/drivers/extcon/extcon-stm32-ipc.c b/drivers/extcon/extcon-stm32-ipc.c
index 59a066b367ffc..25d31877ffa26 100644
--- a/drivers/extcon/extcon-stm32-ipc.c
+++ b/drivers/extcon/extcon-stm32-ipc.c
@@ -199,6 +199,13 @@ static int stm_ipc_sim_write(void *data, u64 val)
 }
 DEFINE_DEBUGFS_ATTRIBUTE(stm_ipc_sim_fops, NULL, stm_ipc_sim_write, "%llu\n");
 
+static void stm_ipc_debugfs_cleanup(void *data)
+{
+	struct dentry *dentry = data;
+
+	debugfs_remove(dentry);
+}
+
 /* Child Connector Platform Device Probe */
 static int stm_usb_connector_probe(struct platform_device *pdev)
 {
@@ -239,8 +246,17 @@ static int stm_usb_connector_probe(struct platform_device *pdev)
 	/* Set up DebugFS for this virtual connector for runtime simulation */
 	parent_priv = dev_get_drvdata(dev->parent);
 	if (parent_priv && parent_priv->debugfs_root) {
+		struct dentry *sim_file;
+
 		snprintf(name, sizeof(name), "usb%d_sim", priv->port_id + 1);
-		debugfs_create_file(name, 0200, parent_priv->debugfs_root, priv, &stm_ipc_sim_fops);
+		sim_file = debugfs_create_file(name, 0200, parent_priv->debugfs_root, priv, &stm_ipc_sim_fops);
+		if (!IS_ERR_OR_NULL(sim_file)) {
+			ret = devm_add_action_or_reset(dev, stm_ipc_debugfs_cleanup, sim_file);
+			if (ret) {
+				dev_err(dev, "Failed to register debugfs cleanup action: %d\n", ret);
+				return ret;
+			}
+		}
 	}
 
 	dev_info(dev, "Registered virtual USB connector on Port %d\n", priv->port_id);

From 9ec6b447a26380355605de3d42ad2f34442e03f3 Mon Sep 17 00:00:00 2001
From: Overdr0ne <scmorris.dev@gmail.com>
Date: Wed, 8 Jul 2026 18:15:20 -0600
Subject: [PATCH 21/22] extcon: stm32-ipc: register platform driver first

Register the platform connector driver stm_usb_connector_driver
before registering the SPI core driver stm_ipc_driver during module
initialization. This ensures child connector devices can bind immediately
when devm_of_platform_populate() is called during SPI device probe,
preventing events from being dropped. Swap unregistration order in exit.
---
 drivers/extcon/extcon-stm32-ipc.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/extcon/extcon-stm32-ipc.c b/drivers/extcon/extcon-stm32-ipc.c
index 25d31877ffa26..c9a91f4fa7726 100644
--- a/drivers/extcon/extcon-stm32-ipc.c
+++ b/drivers/extcon/extcon-stm32-ipc.c
@@ -364,13 +364,13 @@ static int __init stm_ipc_init(void)
 	if (IS_ERR_OR_NULL(stm_ipc_debugfs_dir))
 		stm_ipc_debugfs_dir = NULL;
 
-	ret = spi_register_driver(&stm_ipc_driver);
+	ret = platform_driver_register(&stm_usb_connector_driver);
 	if (ret)
 		goto err_debugfs;
 
-	ret = platform_driver_register(&stm_usb_connector_driver);
+	ret = spi_register_driver(&stm_ipc_driver);
 	if (ret) {
-		spi_unregister_driver(&stm_ipc_driver);
+		platform_driver_unregister(&stm_usb_connector_driver);
 		goto err_debugfs;
 	}
 

From 371883f9befd1edbf443e10ec576107cde2fc1c5 Mon Sep 17 00:00:00 2001
From: Overdr0ne <scmorris.dev@gmail.com>
Date: Wed, 8 Jul 2026 19:37:36 -0600
Subject: [PATCH 22/22] extcon: stm32-ipc: pass device struct directly

Do not dereference edev->dev to log messages in stm_ipc_update_state()
since struct extcon_dev is opaque to client drivers. Instead, store the
device pointer in struct stm_connector_priv and pass it explicitly to
stm_ipc_update_state() from all call sites.
---
 drivers/extcon/extcon-stm32-ipc.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/drivers/extcon/extcon-stm32-ipc.c b/drivers/extcon/extcon-stm32-ipc.c
index c9a91f4fa7726..6f3940402a067 100644
--- a/drivers/extcon/extcon-stm32-ipc.c
+++ b/drivers/extcon/extcon-stm32-ipc.c
@@ -51,6 +51,7 @@ struct stm_ipc_priv {
 
 /* Child connector platform device private structure */
 struct stm_connector_priv {
+	struct device *dev;
 	struct extcon_dev *edev;
 	u8 port_id;
 };
@@ -62,7 +63,7 @@ static const unsigned int stm_usb_cable[] = {
 };
 
 /* Helper to update extcon state based on STM32 reporting */
-static void stm_ipc_update_state(struct extcon_dev *edev, u8 state)
+static void stm_ipc_update_state(struct device *dev, struct extcon_dev *edev, u8 state)
 {
 	int usb_state = extcon_get_state(edev, EXTCON_USB);
 	int host_state = extcon_get_state(edev, EXTCON_USB_HOST);
@@ -70,7 +71,7 @@ static void stm_ipc_update_state(struct extcon_dev *edev, u8 state)
 	bool want_host = false;
 
 	if (usb_state < 0 || host_state < 0) {
-		dev_err_ratelimited(&edev->dev, "Failed to get current extcon state\n");
+		dev_err_ratelimited(dev, "Failed to get current extcon state\n");
 		return;
 	}
 
@@ -91,7 +92,7 @@ static void stm_ipc_update_state(struct extcon_dev *edev, u8 state)
 		/* Fallback to safe disconnected state on protocol error */
 		want_usb = false;
 		want_host = false;
-		dev_warn_ratelimited(&edev->dev, "Invalid USB connector state: %u\n", state);
+		dev_warn_ratelimited(dev, "Invalid USB connector state: %u\n", state);
 		break;
 	}
 
@@ -118,7 +119,7 @@ static int match_and_update_state(struct device *dev, void *data)
 	u8 state = port_info[1];
 
 	if (priv && priv->port_id == port_id) {
-		stm_ipc_update_state(priv->edev, state);
+		stm_ipc_update_state(dev, priv->edev, state);
 		return 1; /* Found and processed, stop iteration */
 	}
 	return 0;
@@ -194,7 +195,7 @@ static int stm_ipc_sim_write(void *data, u64 val)
 	if (val > STM_IPC_USB_STATE_HOST)
 		return -EINVAL;
 
-	stm_ipc_update_state(priv->edev, (u8)val);
+	stm_ipc_update_state(priv->dev, priv->edev, (u8)val);
 	return 0;
 }
 DEFINE_DEBUGFS_ATTRIBUTE(stm_ipc_sim_fops, NULL, stm_ipc_sim_write, "%llu\n");
@@ -220,6 +221,8 @@ static int stm_usb_connector_probe(struct platform_device *pdev)
 	if (!priv)
 		return -ENOMEM;
 
+	priv->dev = dev;
+
 	ret = of_property_read_u32(dev->of_node, "port-id", &val);
 	if (ret) {
 		dev_err(dev, "Missing 'port-id' property\n");