Merge tag 'i2c-for-6.13-rc1-part3' of git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux

Pull i2c component probing support from Wolfram Sang:
 "Add OF component probing.

  Some devices are designed and manufactured with some components having
  multiple drop-in replacement options. These components are often
  connected to the mainboard via ribbon cables, having the same signals
  and pin assignments across all options. These may include the display
  panel and touchscreen on laptops and tablets, and the trackpad on
  laptops. Sometimes which component option is used in a particular
  device can be detected by some firmware provided identifier, other
  times that information is not available, and the kernel has to try to
  probe each device.

  Instead of a delicate dance between drivers and device tree quirks,
  this change introduces a simple I2C component probe function. For a
  given class of devices on the same I2C bus, it will go through all of
  them, doing a simple I2C read transfer and see which one of them
  responds. It will then enable the device that responds"

* tag 'i2c-for-6.13-rc1-part3' of git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux:
  MAINTAINERS: fix typo in I2C OF COMPONENT PROBER
  of: base: Document prefix argument for of_get_next_child_with_prefix()
  i2c: Fix whitespace style issue
  arm64: dts: mediatek: mt8173-elm-hana: Mark touchscreens and trackpads as fail
  platform/chrome: Introduce device tree hardware prober
  i2c: of-prober: Add GPIO support to simple helpers
  i2c: of-prober: Add simple helpers for regulator support
  i2c: Introduce OF component probe function
  of: base: Add for_each_child_of_node_with_prefix()
  of: dynamic: Add of_changeset_update_prop_string

3 files changed, 417 insertions, 1 deletions

diff --git a/drivers/i2c/Makefile b/drivers/i2c/Makefile
index af95d6e7f004..d27de18de46f 100644
--- a/drivers/i2c/Makefile
+++ b/drivers/i2c/Makefile
@@ -9,6 +9,7 @@ i2c-core-y			:= i2c-core-base.o i2c-core-smbus.o
 i2c-core-$(CONFIG_ACPI)		+= i2c-core-acpi.o
 i2c-core-$(CONFIG_I2C_SLAVE)	+= i2c-core-slave.o
 i2c-core-$(CONFIG_OF)		+= i2c-core-of.o
+i2c-core-$(CONFIG_OF_DYNAMIC)	+= i2c-core-of-prober.o
 
 obj-$(CONFIG_I2C_SMBUS)		+= i2c-smbus.o
 obj-$(CONFIG_I2C_CHARDEV)	+= i2c-dev.o
diff --git a/drivers/i2c/i2c-core-of-prober.c b/drivers/i2c/i2c-core-of-prober.c
new file mode 100644
index 000000000000..b9ca785f8b17
--- /dev/null
+++ b/drivers/i2c/i2c-core-of-prober.c
@@ -0,0 +1,415 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Linux I2C core OF component prober code
+ *
+ * Copyright (C) 2024 Google LLC
+ */
+
+#include <linux/cleanup.h>
+#include <linux/delay.h>
+#include <linux/device.h>
+#include <linux/dev_printk.h>
+#include <linux/err.h>
+#include <linux/gpio/consumer.h>
+#include <linux/i2c.h>
+#include <linux/i2c-of-prober.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/regulator/consumer.h>
+#include <linux/slab.h>
+#include <linux/stddef.h>
+
+/*
+ * Some devices, such as Google Hana Chromebooks, are produced by multiple
+ * vendors each using their preferred components. Such components are all
+ * in the device tree. Instead of having all of them enabled and having each
+ * driver separately try and probe its device while fighting over shared
+ * resources, they can be marked as "fail-needs-probe" and have a prober
+ * figure out which one is actually used beforehand.
+ *
+ * This prober assumes such drop-in parts are on the same I2C bus, have
+ * non-conflicting addresses, and can be directly probed by seeing which
+ * address responds.
+ *
+ * TODO:
+ * - Support I2C muxes
+ */
+
+static struct device_node *i2c_of_probe_get_i2c_node(struct device *dev, const char *type)
+{
+	struct device_node *node __free(device_node) = of_find_node_by_name(NULL, type);
+	if (!node) {
+		dev_err(dev, "Could not find %s device node\n", type);
+		return NULL;
+	}
+
+	struct device_node *i2c_node __free(device_node) = of_get_parent(node);
+	if (!of_node_name_eq(i2c_node, "i2c")) {
+		dev_err(dev, "%s device isn't on I2C bus\n", type);
+		return NULL;
+	}
+
+	if (!of_device_is_available(i2c_node)) {
+		dev_err(dev, "I2C controller not available\n");
+		return NULL;
+	}
+
+	return no_free_ptr(i2c_node);
+}
+
+static int i2c_of_probe_enable_node(struct device *dev, struct device_node *node)
+{
+	int ret;
+
+	dev_dbg(dev, "Enabling %pOF\n", node);
+
+	struct of_changeset *ocs __free(kfree) = kzalloc(sizeof(*ocs), GFP_KERNEL);
+	if (!ocs)
+		return -ENOMEM;
+
+	of_changeset_init(ocs);
+	ret = of_changeset_update_prop_string(ocs, node, "status", "okay");
+	if (ret)
+		return ret;
+
+	ret = of_changeset_apply(ocs);
+	if (ret) {
+		/* ocs needs to be explicitly cleaned up before being freed. */
+		of_changeset_destroy(ocs);
+	} else {
+		/*
+		 * ocs is intentionally kept around as it needs to
+		 * exist as long as the change is applied.
+		 */
+		void *ptr __always_unused = no_free_ptr(ocs);
+	}
+
+	return ret;
+}
+
+static const struct i2c_of_probe_ops i2c_of_probe_dummy_ops;
+
+/**
+ * i2c_of_probe_component() - probe for devices of "type" on the same i2c bus
+ * @dev: Pointer to the &struct device of the caller, only used for dev_printk() messages.
+ * @cfg: Pointer to the &struct i2c_of_probe_cfg containing callbacks and other options
+ *       for the prober.
+ * @ctx: Context data for callbacks.
+ *
+ * Probe for possible I2C components of the same "type" (&i2c_of_probe_cfg->type)
+ * on the same I2C bus that have their status marked as "fail-needs-probe".
+ *
+ * Assumes that across the entire device tree the only instances of nodes
+ * with "type" prefixed node names (not including the address portion) are
+ * the ones that need handling for second source components. In other words,
+ * if "type" is "touchscreen", then all device nodes named "touchscreen*"
+ * are the ones that need probing. There cannot be another "touchscreen*"
+ * node that is already enabled.
+ *
+ * Assumes that for each "type" of component, only one actually exists. In
+ * other words, only one matching and existing device will be enabled.
+ *
+ * Context: Process context only. Does non-atomic I2C transfers.
+ *          Should only be used from a driver probe function, as the function
+ *          can return -EPROBE_DEFER if the I2C adapter or other resources
+ *          are unavailable.
+ * Return: 0 on success or no-op, error code otherwise.
+ *         A no-op can happen when it seems like the device tree already
+ *         has components of the type to be probed already enabled. This
+ *         can happen when the device tree had not been updated to mark
+ *         the status of the to-be-probed components as "fail-needs-probe".
+ *         Or this function was already run with the same parameters and
+ *         succeeded in enabling a component. The latter could happen if
+ *         the user had multiple types of components to probe, and one of
+ *         them down the list caused a deferred probe. This is expected
+ *         behavior.
+ */
+int i2c_of_probe_component(struct device *dev, const struct i2c_of_probe_cfg *cfg, void *ctx)
+{
+	const struct i2c_of_probe_ops *ops;
+	const char *type;
+	struct i2c_adapter *i2c;
+	int ret;
+
+	ops = cfg->ops ?: &i2c_of_probe_dummy_ops;
+	type = cfg->type;
+
+	struct device_node *i2c_node __free(device_node) = i2c_of_probe_get_i2c_node(dev, type);
+	if (!i2c_node)
+		return -ENODEV;
+
+	/*
+	 * If any devices of the given "type" are already enabled then this function is a no-op.
+	 * Either the device tree hasn't been modified to work with this probe function, or the
+	 * function had already run before and enabled some component.
+	 */
+	for_each_child_of_node_with_prefix(i2c_node, node, type)
+		if (of_device_is_available(node))
+			return 0;
+
+	i2c = of_get_i2c_adapter_by_node(i2c_node);
+	if (!i2c)
+		return dev_err_probe(dev, -EPROBE_DEFER, "Couldn't get I2C adapter\n");
+
+	/* Grab and enable resources */
+	ret = 0;
+	if (ops->enable)
+		ret = ops->enable(dev, i2c_node, ctx);
+	if (ret)
+		goto out_put_i2c_adapter;
+
+	for_each_child_of_node_with_prefix(i2c_node, node, type) {
+		union i2c_smbus_data data;
+		u32 addr;
+
+		if (of_property_read_u32(node, "reg", &addr))
+			continue;
+		if (i2c_smbus_xfer(i2c, addr, 0, I2C_SMBUS_READ, 0, I2C_SMBUS_BYTE, &data) < 0)
+			continue;
+
+		/* Found a device that is responding */
+		if (ops->cleanup_early)
+			ops->cleanup_early(dev, ctx);
+		ret = i2c_of_probe_enable_node(dev, node);
+		break;
+	}
+
+	if (ops->cleanup)
+		ops->cleanup(dev, ctx);
+out_put_i2c_adapter:
+	i2c_put_adapter(i2c);
+
+	return ret;
+}
+EXPORT_SYMBOL_NS_GPL(i2c_of_probe_component, I2C_OF_PROBER);
+
+static int i2c_of_probe_simple_get_supply(struct device *dev, struct device_node *node,
+					  struct i2c_of_probe_simple_ctx *ctx)
+{
+	const char *supply_name;
+	struct regulator *supply;
+
+	/*
+	 * It's entirely possible for the component's device node to not have the
+	 * regulator supplies. While it does not make sense from a hardware perspective,
+	 * the supplies could be always on or otherwise not modeled in the device tree,
+	 * but the device would still work.
+	 */
+	supply_name = ctx->opts->supply_name;
+	if (!supply_name)
+		return 0;
+
+	supply = of_regulator_get_optional(dev, node, supply_name);
+	if (IS_ERR(supply)) {
+		return dev_err_probe(dev, PTR_ERR(supply),
+				     "Failed to get regulator supply \"%s\" from %pOF\n",
+				     supply_name, node);
+	}
+
+	ctx->supply = supply;
+
+	return 0;
+}
+
+static void i2c_of_probe_simple_put_supply(struct i2c_of_probe_simple_ctx *ctx)
+{
+	regulator_put(ctx->supply);
+	ctx->supply = NULL;
+}
+
+static int i2c_of_probe_simple_enable_regulator(struct device *dev, struct i2c_of_probe_simple_ctx *ctx)
+{
+	int ret;
+
+	if (!ctx->supply)
+		return 0;
+
+	dev_dbg(dev, "Enabling regulator supply \"%s\"\n", ctx->opts->supply_name);
+
+	ret = regulator_enable(ctx->supply);
+	if (ret)
+		return ret;
+
+	if (ctx->opts->post_power_on_delay_ms)
+		msleep(ctx->opts->post_power_on_delay_ms);
+
+	return 0;
+}
+
+static void i2c_of_probe_simple_disable_regulator(struct device *dev, struct i2c_of_probe_simple_ctx *ctx)
+{
+	if (!ctx->supply)
+		return;
+
+	dev_dbg(dev, "Disabling regulator supply \"%s\"\n", ctx->opts->supply_name);
+
+	regulator_disable(ctx->supply);
+}
+
+static int i2c_of_probe_simple_get_gpiod(struct device *dev, struct device_node *node,
+					 struct i2c_of_probe_simple_ctx *ctx)
+{
+	struct fwnode_handle *fwnode = of_fwnode_handle(node);
+	struct gpio_desc *gpiod;
+	const char *con_id;
+
+	/* NULL signals no GPIO needed */
+	if (!ctx->opts->gpio_name)
+		return 0;
+
+	/* An empty string signals an unnamed GPIO */
+	if (!ctx->opts->gpio_name[0])
+		con_id = NULL;
+	else
+		con_id = ctx->opts->gpio_name;
+
+	gpiod = fwnode_gpiod_get_index(fwnode, con_id, 0, GPIOD_ASIS, "i2c-of-prober");
+	if (IS_ERR(gpiod))
+		return PTR_ERR(gpiod);
+
+	ctx->gpiod = gpiod;
+
+	return 0;
+}
+
+static void i2c_of_probe_simple_put_gpiod(struct i2c_of_probe_simple_ctx *ctx)
+{
+	gpiod_put(ctx->gpiod);
+	ctx->gpiod = NULL;
+}
+
+static int i2c_of_probe_simple_set_gpio(struct device *dev, struct i2c_of_probe_simple_ctx *ctx)
+{
+	int ret;
+
+	if (!ctx->gpiod)
+		return 0;
+
+	dev_dbg(dev, "Configuring GPIO\n");
+
+	ret = gpiod_direction_output(ctx->gpiod, ctx->opts->gpio_assert_to_enable);
+	if (ret)
+		return ret;
+
+	if (ctx->opts->post_gpio_config_delay_ms)
+		msleep(ctx->opts->post_gpio_config_delay_ms);
+
+	return 0;
+}
+
+static void i2c_of_probe_simple_disable_gpio(struct device *dev, struct i2c_of_probe_simple_ctx *ctx)
+{
+	gpiod_set_value(ctx->gpiod, !ctx->opts->gpio_assert_to_enable);
+}
+
+/**
+ * i2c_of_probe_simple_enable - Simple helper for I2C OF prober to get and enable resources
+ * @dev: Pointer to the &struct device of the caller, only used for dev_printk() messages
+ * @bus_node: Pointer to the &struct device_node of the I2C adapter.
+ * @data: Pointer to &struct i2c_of_probe_simple_ctx helper context.
+ *
+ * If &i2c_of_probe_simple_opts->supply_name is given, request the named regulator supply.
+ * If &i2c_of_probe_simple_opts->gpio_name is given, request the named GPIO. Or if it is
+ * the empty string, request the unnamed GPIO.
+ * If a regulator supply was found, enable that regulator.
+ * If a GPIO line was found, configure the GPIO line to output and set value
+ * according to given options.
+ *
+ * Return: %0 on success or no-op, or a negative error number on failure.
+ */
+int i2c_of_probe_simple_enable(struct device *dev, struct device_node *bus_node, void *data)
+{
+	struct i2c_of_probe_simple_ctx *ctx = data;
+	struct device_node *node;
+	const char *compat;
+	int ret;
+
+	dev_dbg(dev, "Requesting resources for components under I2C bus %pOF\n", bus_node);
+
+	if (!ctx || !ctx->opts)
+		return -EINVAL;
+
+	compat = ctx->opts->res_node_compatible;
+	if (!compat)
+		return -EINVAL;
+
+	node = of_get_compatible_child(bus_node, compat);
+	if (!node)
+		return dev_err_probe(dev, -ENODEV, "No device compatible with \"%s\" found\n",
+				     compat);
+
+	ret = i2c_of_probe_simple_get_supply(dev, node, ctx);
+	if (ret)
+		goto out_put_node;
+
+	ret = i2c_of_probe_simple_get_gpiod(dev, node, ctx);
+	if (ret)
+		goto out_put_supply;
+
+	ret = i2c_of_probe_simple_enable_regulator(dev, ctx);
+	if (ret)
+		goto out_put_gpiod;
+
+	ret = i2c_of_probe_simple_set_gpio(dev, ctx);
+	if (ret)
+		goto out_disable_regulator;
+
+	return 0;
+
+out_disable_regulator:
+	i2c_of_probe_simple_disable_regulator(dev, ctx);
+out_put_gpiod:
+	i2c_of_probe_simple_put_gpiod(ctx);
+out_put_supply:
+	i2c_of_probe_simple_put_supply(ctx);
+out_put_node:
+	of_node_put(node);
+	return ret;
+}
+EXPORT_SYMBOL_NS_GPL(i2c_of_probe_simple_enable, I2C_OF_PROBER);
+
+/**
+ * i2c_of_probe_simple_cleanup_early - \
+ *	Simple helper for I2C OF prober to release GPIOs before component is enabled
+ * @dev: Pointer to the &struct device of the caller; unused.
+ * @data: Pointer to &struct i2c_of_probe_simple_ctx helper context.
+ *
+ * GPIO descriptors are exclusive and have to be released before the
+ * actual driver probes so that the latter can acquire them.
+ */
+void i2c_of_probe_simple_cleanup_early(struct device *dev, void *data)
+{
+	struct i2c_of_probe_simple_ctx *ctx = data;
+
+	i2c_of_probe_simple_put_gpiod(ctx);
+}
+EXPORT_SYMBOL_NS_GPL(i2c_of_probe_simple_cleanup_early, I2C_OF_PROBER);
+
+/**
+ * i2c_of_probe_simple_cleanup - Clean up and release resources for I2C OF prober simple helpers
+ * @dev: Pointer to the &struct device of the caller, only used for dev_printk() messages
+ * @data: Pointer to &struct i2c_of_probe_simple_ctx helper context.
+ *
+ * * If a GPIO line was found and not yet released, set its value to the opposite of that
+ *   set in i2c_of_probe_simple_enable() and release it.
+ * * If a regulator supply was found, disable that regulator and release it.
+ */
+void i2c_of_probe_simple_cleanup(struct device *dev, void *data)
+{
+	struct i2c_of_probe_simple_ctx *ctx = data;
+
+	/* GPIO operations here are no-ops if i2c_of_probe_simple_cleanup_early was called. */
+	i2c_of_probe_simple_disable_gpio(dev, ctx);
+	i2c_of_probe_simple_put_gpiod(ctx);
+
+	i2c_of_probe_simple_disable_regulator(dev, ctx);
+	i2c_of_probe_simple_put_supply(ctx);
+}
+EXPORT_SYMBOL_NS_GPL(i2c_of_probe_simple_cleanup, I2C_OF_PROBER);
+
+struct i2c_of_probe_ops i2c_of_probe_simple_ops = {
+	.enable = i2c_of_probe_simple_enable,
+	.cleanup_early = i2c_of_probe_simple_cleanup_early,
+	.cleanup = i2c_of_probe_simple_cleanup,
+};
+EXPORT_SYMBOL_NS_GPL(i2c_of_probe_simple_ops, I2C_OF_PROBER);
diff --git a/drivers/i2c/i2c-core-smbus.c b/drivers/i2c/i2c-core-smbus.c
index 0a6bdc6df172..e73afbefe222 100644
--- a/drivers/i2c/i2c-core-smbus.c
+++ b/drivers/i2c/i2c-core-smbus.c
@@ -122,7 +122,7 @@ EXPORT_SYMBOL(i2c_smbus_read_byte);
 s32 i2c_smbus_write_byte(const struct i2c_client *client, u8 value)
 {
 	return i2c_smbus_xfer(client->adapter, client->addr, client->flags,
-	                      I2C_SMBUS_WRITE, value, I2C_SMBUS_BYTE, NULL);
+			      I2C_SMBUS_WRITE, value, I2C_SMBUS_BYTE, NULL);
 }
 EXPORT_SYMBOL(i2c_smbus_write_byte);