1// SPDX-License-Identifier: GPL-2.0
  2/**
  3 * Device connections
  4 *
  5 * Copyright (C) 2018 Intel Corporation
  6 * Author: Heikki Krogerus <heikki.krogerus@linux.intel.com>
  7 */
  8
  9#include <linux/device.h>
 10
 11static DEFINE_MUTEX(devcon_lock);
 12static LIST_HEAD(devcon_list);
 13
 14/**
 15 * device_connection_find_match - Find physical connection to a device
 16 * @dev: Device with the connection
 17 * @con_id: Identifier for the connection
 18 * @data: Data for the match function
 19 * @match: Function to check and convert the connection description
 20 *
 21 * Find a connection with unique identifier @con_id between @dev and another
 22 * device. @match will be used to convert the connection description to data the
 23 * caller is expecting to be returned.
 24 */
 25void *device_connection_find_match(struct device *dev, const char *con_id,
 26			       void *data,
 27			       void *(*match)(struct device_connection *con,
 28					      int ep, void *data))
 29{
 30	const char *devname = dev_name(dev);
 31	struct device_connection *con;
 32	void *ret = NULL;
 33	int ep;
 34
 35	if (!match)
 36		return NULL;
 37
 38	mutex_lock(&devcon_lock);
 39
 40	list_for_each_entry(con, &devcon_list, list) {
 41		ep = match_string(con->endpoint, 2, devname);
 42		if (ep < 0)
 43			continue;
 44
 45		if (con_id && strcmp(con->id, con_id))
 46			continue;
 47
 48		ret = match(con, !ep, data);
 49		if (ret)
 50			break;
 51	}
 52
 53	mutex_unlock(&devcon_lock);
 54
 55	return ret;
 56}
 57EXPORT_SYMBOL_GPL(device_connection_find_match);
 58
 59extern struct bus_type platform_bus_type;
 60extern struct bus_type pci_bus_type;
 61extern struct bus_type i2c_bus_type;
 62extern struct bus_type spi_bus_type;
 63
 64static struct bus_type *generic_match_buses[] = {
 65	&platform_bus_type,
 66#ifdef CONFIG_PCI
 67	&pci_bus_type,
 68#endif
 69#ifdef CONFIG_I2C
 70	&i2c_bus_type,
 71#endif
 72#ifdef CONFIG_SPI_MASTER
 73	&spi_bus_type,
 74#endif
 75	NULL,
 76};
 77
 78/* This tries to find the device from the most common bus types by name. */
 79static void *generic_match(struct device_connection *con, int ep, void *data)
 80{
 81	struct bus_type *bus;
 82	struct device *dev;
 83
 84	for (bus = generic_match_buses[0]; bus; bus++) {
 85		dev = bus_find_device_by_name(bus, NULL, con->endpoint[ep]);
 86		if (dev)
 87			return dev;
 88	}
 89
 90	/*
 91	 * We only get called if a connection was found, tell the caller to
 92	 * wait for the other device to show up.
 93	 */
 94	return ERR_PTR(-EPROBE_DEFER);
 95}
 96
 97/**
 98 * device_connection_find - Find two devices connected together
 99 * @dev: Device with the connection
100 * @con_id: Identifier for the connection
101 *
102 * Find a connection with unique identifier @con_id between @dev and
103 * another device. On success returns handle to the device that is connected
104 * to @dev, with the reference count for the found device incremented. Returns
105 * NULL if no matching connection was found, or ERR_PTR(-EPROBE_DEFER) when a
106 * connection was found but the other device has not been enumerated yet.
107 */
108struct device *device_connection_find(struct device *dev, const char *con_id)
109{
110	return device_connection_find_match(dev, con_id, NULL, generic_match);
111}
112EXPORT_SYMBOL_GPL(device_connection_find);
113
114/**
115 * device_connection_add - Register a connection description
116 * @con: The connection description to be registered
117 */
118void device_connection_add(struct device_connection *con)
119{
120	mutex_lock(&devcon_lock);
121	list_add_tail(&con->list, &devcon_list);
122	mutex_unlock(&devcon_lock);
123}
124EXPORT_SYMBOL_GPL(device_connection_add);
125
126/**
127 * device_connections_remove - Unregister connection description
128 * @con: The connection description to be unregistered
129 */
130void device_connection_remove(struct device_connection *con)
131{
132	mutex_lock(&devcon_lock);
133	list_del(&con->list);
134	mutex_unlock(&devcon_lock);
135}
136EXPORT_SYMBOL_GPL(device_connection_remove);