LXR linux/drivers/base/devcon.c

   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);
 137