[PATCH 07/12] gpiolib: acpi: Add dedicated Operation Region module

["Marco Scardovi (scardracs)" <mscardovi95@gmail.com>]

Assisted-by: Antigravity:gemini-3-flash
Signed-off-by: Marco Scardovi <mscardovi95@gmail.com>
---
 drivers/gpio/Makefile                |   2 +-
 drivers/gpio/gpiolib-acpi-opregion.c | 175 +++++++++++++++++++++++++++
 2 files changed, 176 insertions(+), 1 deletion(-)
 create mode 100644 drivers/gpio/gpiolib-acpi-opregion.c

diff --git a/drivers/gpio/Makefile b/drivers/gpio/Makefile
index b267598b517d..1a416305465b 100644
--- a/drivers/gpio/Makefile
+++ b/drivers/gpio/Makefile
@@ -10,7 +10,7 @@ obj-$(CONFIG_OF_GPIO)		+= gpiolib-of.o
 obj-$(CONFIG_GPIO_CDEV)		+= gpiolib-cdev.o
 obj-$(CONFIG_GPIO_SYSFS)	+= gpiolib-sysfs.o
 obj-$(CONFIG_GPIO_ACPI)		+= gpiolib-acpi.o
-gpiolib-acpi-y			:= gpiolib-acpi-core.o gpiolib-acpi-quirks.o
+gpiolib-acpi-y			:= gpiolib-acpi-core.o gpiolib-acpi-quirks.o gpiolib-acpi-opregion.o
 obj-$(CONFIG_GPIOLIB)		+= gpiolib-swnode.o
 obj-$(CONFIG_GPIO_SHARED)	+= gpiolib-shared.o
 
diff --git a/drivers/gpio/gpiolib-acpi-opregion.c b/drivers/gpio/gpiolib-acpi-opregion.c
new file mode 100644
index 000000000000..77b1ee32ddce
--- /dev/null
+++ b/drivers/gpio/gpiolib-acpi-opregion.c
@@ -0,0 +1,175 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * ACPI Operation Region helper for GPIO API
+ *
+ * Copyright (C) 2026, Intel Corporation
+ */
+
+#include <linux/acpi.h>
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/gpio/driver.h>
+#include <linux/mutex.h>
+#include <linux/printk.h>
+#include <linux/slab.h>
+
+#include "gpiolib.h"
+#include "gpiolib-acpi.h"
+
+static acpi_status
+acpi_gpio_adr_space_handler(u32 function, acpi_physical_address address,
+			    u32 bits, u64 *value, void *handler_context,
+			    void *region_context)
+{
+	struct acpi_gpio_chip *achip = region_context;
+	struct gpio_chip *chip = achip->chip;
+	struct acpi_resource_gpio *agpio;
+	struct acpi_resource *ares;
+	u16 pin_index = address;
+	acpi_status status;
+	int length;
+	int i;
+
+	status = acpi_buffer_to_resource(achip->conn_info.connection,
+					 achip->conn_info.length, &ares);
+	if (ACPI_FAILURE(status))
+		return status;
+
+	if (WARN_ON(ares->type != ACPI_RESOURCE_TYPE_GPIO)) {
+		ACPI_FREE(ares);
+		return AE_BAD_PARAMETER;
+	}
+
+	agpio = &ares->data.gpio;
+
+	if (WARN_ON(agpio->io_restriction == ACPI_IO_RESTRICT_INPUT &&
+	    function == ACPI_WRITE)) {
+		ACPI_FREE(ares);
+		return AE_BAD_PARAMETER;
+	}
+
+	if (pin_index >= agpio->pin_table_length) {
+		ACPI_FREE(ares);
+		return AE_BAD_PARAMETER;
+	}
+
+	length = min(agpio->pin_table_length, pin_index + bits);
+	for (i = pin_index; i < length; ++i) {
+		unsigned int pin = agpio->pin_table[i];
+		struct acpi_gpio_connection *conn;
+		struct gpio_desc *desc;
+		u16 word, shift;
+		bool found;
+
+		mutex_lock(&achip->conn_lock);
+
+		found = false;
+		list_for_each_entry(conn, &achip->conns, node) {
+			if (conn->pin == pin) {
+				found = true;
+				desc = conn->desc;
+				break;
+			}
+		}
+
+		/*
+		 * The same GPIO can be shared between operation region and
+		 * event but only if the access here is ACPI_READ. In that
+		 * case we "borrow" the event GPIO instead.
+		 */
+		if (!found && agpio->shareable == ACPI_SHARED &&
+		     function == ACPI_READ) {
+			struct acpi_gpio_event *event;
+
+			list_for_each_entry(event, &achip->events, node) {
+				if (event->pin == pin) {
+					desc = event->desc;
+					found = true;
+					break;
+				}
+			}
+		}
+
+		if (!found) {
+			desc = acpi_request_own_gpiod(chip, agpio, i, "ACPI:OpRegion");
+			if (IS_ERR(desc)) {
+				mutex_unlock(&achip->conn_lock);
+				status = AE_ERROR;
+				goto out;
+			}
+
+			conn = kzalloc_obj(*conn);
+			if (!conn) {
+				gpiochip_free_own_desc(desc);
+				mutex_unlock(&achip->conn_lock);
+				status = AE_NO_MEMORY;
+				goto out;
+			}
+
+			conn->pin = pin;
+			conn->desc = desc;
+			list_add_tail(&conn->node, &achip->conns);
+		}
+
+		mutex_unlock(&achip->conn_lock);
+
+		/*
+		 * For the cases when OperationRegion() consists of more than
+		 * 64 bits calculate the word and bit shift to use that one to
+		 * access the value.
+		 */
+		word = i / 64;
+		shift = i % 64;
+
+		if (function == ACPI_WRITE) {
+			gpiod_set_raw_value_cansleep(desc, value[word] & BIT_ULL(shift));
+		} else {
+			if (gpiod_get_raw_value_cansleep(desc))
+				value[word] |= BIT_ULL(shift);
+			else
+				value[word] &= ~BIT_ULL(shift);
+		}
+	}
+
+out:
+	ACPI_FREE(ares);
+	return status;
+}
+
+void acpi_gpiochip_request_regions(struct acpi_gpio_chip *achip)
+{
+	struct gpio_chip *chip = achip->chip;
+	acpi_handle handle = ACPI_HANDLE(chip->parent);
+	acpi_status status;
+
+	INIT_LIST_HEAD(&achip->conns);
+	mutex_init(&achip->conn_lock);
+
+	status = acpi_install_address_space_handler(handle, ACPI_ADR_SPACE_GPIO,
+						    acpi_gpio_adr_space_handler,
+						    NULL, achip);
+	if (ACPI_FAILURE(status))
+		dev_err(chip->parent,
+			"Failed to install GPIO OpRegion handler\n");
+}
+
+void acpi_gpiochip_free_regions(struct acpi_gpio_chip *achip)
+{
+	struct gpio_chip *chip = achip->chip;
+	acpi_handle handle = ACPI_HANDLE(chip->parent);
+	struct acpi_gpio_connection *conn, *tmp;
+	acpi_status status;
+
+	status = acpi_remove_address_space_handler(handle, ACPI_ADR_SPACE_GPIO,
+						   acpi_gpio_adr_space_handler);
+	if (ACPI_FAILURE(status)) {
+		dev_err(chip->parent,
+			"Failed to remove GPIO OpRegion handler\n");
+	}
+
+	list_for_each_entry_safe_reverse(conn, tmp, &achip->conns, node) {
+		gpiochip_free_own_desc(conn->desc);
+		list_del(&conn->node);
+		kfree(conn);
+	}
+}
-- 
2.54.0