Linux kernel mirror (for testing)
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linux
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);