[v2] gpio: Add ChromeOS EC GPIO driver

diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
index 1301cec94f12..f6792c814e84 100644
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -1240,6 +1240,16 @@  config GPIO_BD9571MWV
 	  This driver can also be built as a module. If so, the module
 	  will be called gpio-bd9571mwv.
 
+config GPIO_CROS_EC
+	tristate "ChromeOS EC GPIO support"
+	depends on CROS_EC
+	help
+	  GPIO driver for the ChromeOS Embedded Controller (EC). GPIOs
+	  cannot be set unless the system is unlocked.
+
+	  This driver can also be built as a module. If so, the module
+	  will be called gpio-cros-ec.
+
 config GPIO_CRYSTAL_COVE
 	tristate "GPIO support for Crystal Cove PMIC"
 	depends on (X86 || COMPILE_TEST) && INTEL_SOC_PMIC
diff --git a/drivers/gpio/Makefile b/drivers/gpio/Makefile
index 9e40af196aae..7ae4d81de1df 100644
--- a/drivers/gpio/Makefile
+++ b/drivers/gpio/Makefile
@@ -46,6 +46,7 @@  obj-$(CONFIG_GPIO_BT8XX)		+= gpio-bt8xx.o
 obj-$(CONFIG_GPIO_CADENCE)		+= gpio-cadence.o
 obj-$(CONFIG_GPIO_CLPS711X)		+= gpio-clps711x.o
 obj-$(CONFIG_GPIO_SNPS_CREG)		+= gpio-creg-snps.o
+obj-$(CONFIG_GPIO_CROS_EC)		+= gpio-cros-ec.o
 obj-$(CONFIG_GPIO_CRYSTAL_COVE)		+= gpio-crystalcove.o
 obj-$(CONFIG_GPIO_CS5535)		+= gpio-cs5535.o
 obj-$(CONFIG_GPIO_DA9052)		+= gpio-da9052.o
diff --git a/drivers/gpio/gpio-cros-ec.c b/drivers/gpio/gpio-cros-ec.c
new file mode 100644
index 000000000000..842e1c060414
--- /dev/null
+++ b/drivers/gpio/gpio-cros-ec.c
@@ -0,0 +1,209 @@ 
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright 2024 Google LLC
+ *
+ * This driver provides the ability to control GPIOs on the Chrome OS EC.
+ * There isn't any direction control, and setting values on GPIOs is only
+ * possible when the system is unlocked.
+ */
+
+#include <linux/bitops.h>
+#include <linux/device.h>
+#include <linux/errno.h>
+#include <linux/gpio/driver.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/platform_data/cros_ec_commands.h>
+#include <linux/platform_data/cros_ec_proto.h>
+#include <linux/platform_device.h>
+#include <linux/property.h>
+#include <linux/slab.h>
+
+/* Prefix all names to avoid collisions with EC <-> AP nets */
+static const char cros_ec_gpio_prefix[] = "EC:";
+
+/* Setting gpios is only supported when the system is unlocked */
+static void cros_ec_gpio_set(struct gpio_chip *gc, unsigned int gpio, int val)
+{
+	const char *name = gc->names[gpio] + strlen(cros_ec_gpio_prefix);
+	struct cros_ec_device *cros_ec = gpiochip_get_data(gc);
+	struct ec_params_gpio_set params = {
+		.val = val,
+	};
+	int ret;
+	ssize_t copied;
+
+	copied = strscpy(params.name, name, sizeof(params.name));
+	if (copied < 0)
+		return;
+
+	ret = cros_ec_cmd(cros_ec, 0, EC_CMD_GPIO_SET, &params,
+			  sizeof(params), NULL, 0);
+	if (ret < 0)
+		dev_err(gc->parent, "error setting gpio%d (%s) on EC: %d\n", gpio, name, ret);
+}
+
+static int cros_ec_gpio_get(struct gpio_chip *gc, unsigned int gpio)
+{
+	const char *name = gc->names[gpio] + strlen(cros_ec_gpio_prefix);
+	struct cros_ec_device *cros_ec = gpiochip_get_data(gc);
+	struct ec_params_gpio_get params;
+	struct ec_response_gpio_get response;
+	int ret;
+	ssize_t copied;
+
+	copied = strscpy(params.name, name, sizeof(params.name));
+	if (copied < 0)
+		return -EINVAL;
+
+	ret = cros_ec_cmd(cros_ec, 0, EC_CMD_GPIO_GET, &params,
+			  sizeof(params), &response, sizeof(response));
+	if (ret < 0) {
+		dev_err(gc->parent, "error getting gpio%d (%s) on EC: %d\n", gpio, name, ret);
+		return ret;
+	}
+
+	return response.val;
+}
+
+#define CROS_EC_GPIO_INPUT         BIT(8)
+#define CROS_EC_GPIO_OUTPUT        BIT(9)
+
+static int cros_ec_gpio_get_direction(struct gpio_chip *gc, unsigned int gpio)
+{
+	const char *name = gc->names[gpio] + strlen(cros_ec_gpio_prefix);
+	struct cros_ec_device *cros_ec = gpiochip_get_data(gc);
+	struct ec_params_gpio_get_v1 params = {
+		.subcmd = EC_GPIO_GET_INFO,
+		.get_info.index = gpio,
+	};
+	struct ec_response_gpio_get_v1 response;
+	int ret;
+
+	ret = cros_ec_cmd(cros_ec, 1, EC_CMD_GPIO_GET, &params,
+			  sizeof(params), &response, sizeof(response));
+	if (ret < 0) {
+		dev_err(gc->parent, "error getting direction of gpio%d (%s) on EC: %d\n", gpio, name, ret);
+		return ret;
+	}
+
+	if (response.get_info.flags & CROS_EC_GPIO_INPUT)
+		return GPIO_LINE_DIRECTION_IN;
+
+	if (response.get_info.flags & CROS_EC_GPIO_OUTPUT)
+		return GPIO_LINE_DIRECTION_OUT;
+
+	return -EINVAL;
+}
+
+/* Query EC for all gpio line names */
+static int cros_ec_gpio_init_names(struct cros_ec_device *cros_ec, struct gpio_chip *gc)
+{
+	struct ec_params_gpio_get_v1 params = {
+		.subcmd = EC_GPIO_GET_INFO,
+	};
+	struct ec_response_gpio_get_v1 response;
+	int ret, i;
+	/* EC may not NUL terminate */
+	size_t name_len = strlen(cros_ec_gpio_prefix) + sizeof(response.get_info.name) + 1;
+	ssize_t copied;
+	const char **names;
+	char *str;
+
+	names = devm_kcalloc(gc->parent, gc->ngpio, sizeof(*names), GFP_KERNEL);
+	if (!names)
+		return -ENOMEM;
+	gc->names = names;
+
+	str = devm_kcalloc(gc->parent, gc->ngpio, name_len, GFP_KERNEL);
+	if (!str)
+		return -ENOMEM;
+
+	/* Get gpio line names one at a time */
+	for (i = 0; i < gc->ngpio; i++) {
+		params.get_info.index = i;
+		ret = cros_ec_cmd(cros_ec, 1, EC_CMD_GPIO_GET, &params,
+				  sizeof(params), &response, sizeof(response));
+		if (ret < 0) {
+			dev_err_probe(gc->parent, ret, "error getting gpio%d info\n", i);
+			return ret;
+		}
+
+		names[i] = str;
+		copied = scnprintf(str, name_len, "%s%s", cros_ec_gpio_prefix,
+				   response.get_info.name);
+		if (copied < 0)
+			return copied;
+
+		str += copied + 1;
+	}
+
+	return 0;
+}
+
+/* Query EC for number of gpios */
+static int cros_ec_gpio_ngpios(struct cros_ec_device *cros_ec)
+{
+	struct ec_params_gpio_get_v1 params = {
+		.subcmd = EC_GPIO_GET_COUNT,
+	};
+	struct ec_response_gpio_get_v1 response;
+	int ret;
+
+	ret = cros_ec_cmd(cros_ec, 1, EC_CMD_GPIO_GET, &params,
+			  sizeof(params), &response, sizeof(response));
+	if (ret < 0)
+		return ret;
+
+	return response.get_count.val;
+}
+
+static int cros_ec_gpio_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct device *parent = dev->parent;
+	struct cros_ec_dev *ec_dev = dev_get_drvdata(parent);
+	struct cros_ec_device *cros_ec = ec_dev->ec_dev;
+	struct gpio_chip *gc;
+	int ngpios;
+	int ret;
+
+	/* Use the fwnode from the protocol device, e.g. cros-ec-spi */
+	device_set_node(dev, dev_fwnode(cros_ec->dev));
+
+	ngpios = cros_ec_gpio_ngpios(cros_ec);
+	if (ngpios < 0) {
+		dev_err_probe(dev, ngpios, "error getting gpio count\n");
+		return ngpios;
+	}
+
+	gc = devm_kzalloc(dev, sizeof(*gc), GFP_KERNEL);
+	if (!gc)
+		return -ENOMEM;
+
+	gc->ngpio = ngpios;
+	gc->parent = dev;
+	ret = cros_ec_gpio_init_names(cros_ec, gc);
+	if (ret)
+		return ret;
+
+	gc->can_sleep = true;
+	gc->label = dev_name(dev);
+	gc->base = -1;
+	gc->set = cros_ec_gpio_set;
+	gc->get = cros_ec_gpio_get;
+	gc->get_direction = cros_ec_gpio_get_direction;
+
+	return devm_gpiochip_add_data(dev, gc, cros_ec);
+}
+
+static struct platform_driver cros_ec_gpio_driver = {
+	.probe = cros_ec_gpio_probe,
+	.driver = {
+		.name = "cros-ec-gpio",
+	},
+};
+module_platform_driver(cros_ec_gpio_driver);
+
+MODULE_DESCRIPTION("ChromeOS EC GPIO Driver");
+MODULE_LICENSE("GPL");