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

2 files changed, 153 insertions, 0 deletions

diff --git a/include/linux/i2c-of-prober.h b/include/linux/i2c-of-prober.h
new file mode 100644
index 000000000000..bb6d47f50ee5
--- /dev/null
+++ b/include/linux/i2c-of-prober.h
@@ -0,0 +1,140 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Definitions for the Linux I2C OF component prober
+ *
+ * Copyright (C) 2024 Google LLC
+ */
+
+#ifndef _LINUX_I2C_OF_PROBER_H
+#define _LINUX_I2C_OF_PROBER_H
+
+#include <linux/kconfig.h>
+#include <linux/types.h>
+
+struct device;
+struct device_node;
+
+/**
+ * struct i2c_of_probe_ops - I2C OF component prober callbacks
+ *
+ * A set of callbacks to be used by i2c_of_probe_component().
+ *
+ * All callbacks are optional. Callbacks are called only once per run, and are
+ * used in the order they are defined in this structure.
+ *
+ * All callbacks that have return values shall return %0 on success,
+ * or a negative error number on failure.
+ *
+ * The @dev parameter passed to the callbacks is the same as @dev passed to
+ * i2c_of_probe_component(). It should only be used for dev_printk() calls
+ * and nothing else, especially not managed device resource (devres) APIs.
+ */
+struct i2c_of_probe_ops {
+	/**
+	 * @enable: Retrieve and enable resources so that the components respond to probes.
+	 *
+	 * It is OK for this callback to return -EPROBE_DEFER since the intended use includes
+	 * retrieving resources and enables them. Resources should be reverted to their initial
+	 * state and released before returning if this fails.
+	 */
+	int (*enable)(struct device *dev, struct device_node *bus_node, void *data);
+
+	/**
+	 * @cleanup_early: Release exclusive resources prior to calling probe() on a
+	 *		   detected component.
+	 *
+	 * Only called if a matching component is actually found. If none are found,
+	 * resources that would have been released in this callback should be released in
+	 * @free_resourcs_late instead.
+	 */
+	void (*cleanup_early)(struct device *dev, void *data);
+
+	/**
+	 * @cleanup: Opposite of @enable to balance refcounts and free resources after probing.
+	 *
+	 * Should check if resources were already freed by @cleanup_early.
+	 */
+	void (*cleanup)(struct device *dev, void *data);
+};
+
+/**
+ * struct i2c_of_probe_cfg - I2C OF component prober configuration
+ * @ops: Callbacks for the prober to use.
+ * @type: A string to match the device node name prefix to probe for.
+ */
+struct i2c_of_probe_cfg {
+	const struct i2c_of_probe_ops *ops;
+	const char *type;
+};
+
+#if IS_ENABLED(CONFIG_OF_DYNAMIC)
+
+int i2c_of_probe_component(struct device *dev, const struct i2c_of_probe_cfg *cfg, void *ctx);
+
+/**
+ * DOC: I2C OF component prober simple helpers
+ *
+ * Components such as trackpads are commonly connected to a devices baseboard
+ * with a 6-pin ribbon cable. That gives at most one voltage supply and one
+ * GPIO (commonly a "enable" or "reset" line) besides the I2C bus, interrupt
+ * pin, and common ground. Touchscreens, while integrated into the display
+ * panel's connection, typically have the same set of connections.
+ *
+ * A simple set of helpers are provided here for use with the I2C OF component
+ * prober. This implementation targets such components, allowing for at most
+ * one regulator supply.
+ *
+ * The following helpers are provided:
+ * * i2c_of_probe_simple_enable()
+ * * i2c_of_probe_simple_cleanup_early()
+ * * i2c_of_probe_simple_cleanup()
+ */
+
+/**
+ * struct i2c_of_probe_simple_opts - Options for simple I2C component prober callbacks
+ * @res_node_compatible: Compatible string of device node to retrieve resources from.
+ * @supply_name: Name of regulator supply.
+ * @gpio_name: Name of GPIO. NULL if no GPIO line is used. Empty string ("") if GPIO
+ *	       line is unnamed.
+ * @post_power_on_delay_ms: Delay after regulators are powered on. Passed to msleep().
+ * @post_gpio_config_delay_ms: Delay after GPIO is configured. Passed to msleep().
+ * @gpio_assert_to_enable: %true if GPIO should be asserted, i.e. set to logical high,
+ *			   to enable the component.
+ *
+ * This describes power sequences common for the class of components supported by the
+ * simple component prober:
+ * * @gpio_name is configured to the non-active setting according to @gpio_assert_to_enable.
+ * * @supply_name regulator supply is enabled.
+ * * Wait for @post_power_on_delay_ms to pass.
+ * * @gpio_name is configured to the active setting according to @gpio_assert_to_enable.
+ * * Wait for @post_gpio_config_delay_ms to pass.
+ */
+struct i2c_of_probe_simple_opts {
+	const char *res_node_compatible;
+	const char *supply_name;
+	const char *gpio_name;
+	unsigned int post_power_on_delay_ms;
+	unsigned int post_gpio_config_delay_ms;
+	bool gpio_assert_to_enable;
+};
+
+struct gpio_desc;
+struct regulator;
+
+struct i2c_of_probe_simple_ctx {
+	/* public: provided by user before helpers are used. */
+	const struct i2c_of_probe_simple_opts *opts;
+	/* private: internal fields for helpers. */
+	struct regulator *supply;
+	struct gpio_desc *gpiod;
+};
+
+int i2c_of_probe_simple_enable(struct device *dev, struct device_node *bus_node, void *data);
+void i2c_of_probe_simple_cleanup_early(struct device *dev, void *data);
+void i2c_of_probe_simple_cleanup(struct device *dev, void *data);
+
+extern struct i2c_of_probe_ops i2c_of_probe_simple_ops;
+
+#endif /* IS_ENABLED(CONFIG_OF_DYNAMIC) */
+
+#endif /* _LINUX_I2C_OF_PROBER_H */
diff --git a/include/linux/of.h b/include/linux/of.h
index 086a60f3b8a6..f921786cb8ac 100644
--- a/include/linux/of.h
+++ b/include/linux/of.h
@@ -289,6 +289,9 @@ extern struct device_node *of_get_parent(const struct device_node *node);
 extern struct device_node *of_get_next_parent(struct device_node *node);
 extern struct device_node *of_get_next_child(const struct device_node *node,
 					     struct device_node *prev);
+extern struct device_node *of_get_next_child_with_prefix(const struct device_node *node,
+							 struct device_node *prev,
+							 const char *prefix);
 extern struct device_node *of_get_next_available_child(
 	const struct device_node *node, struct device_node *prev);
 extern struct device_node *of_get_next_reserved_child(
@@ -1468,6 +1471,12 @@ static inline int of_property_read_s32(const struct device_node *np,
 	     child != NULL;						\
 	     child = of_get_next_child(parent, child))
 
+#define for_each_child_of_node_with_prefix(parent, child, prefix)	\
+	for (struct device_node *child __free(device_node) =		\
+	     of_get_next_child_with_prefix(parent, NULL, prefix);	\
+	     child != NULL;						\
+	     child = of_get_next_child_with_prefix(parent, child, prefix))
+
 #define for_each_available_child_of_node(parent, child) \
 	for (child = of_get_next_available_child(parent, NULL); child != NULL; \
 	     child = of_get_next_available_child(parent, child))
@@ -1651,6 +1660,10 @@ static inline int of_changeset_add_prop_u32(struct of_changeset *ocs,
 	return of_changeset_add_prop_u32_array(ocs, np, prop_name, &val, 1);
 }
 
+int of_changeset_update_prop_string(struct of_changeset *ocs,
+				    struct device_node *np,
+				    const char *prop_name, const char *str);
+
 int of_changeset_add_prop_bool(struct of_changeset *ocs, struct device_node *np,
 			       const char *prop_name);