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Linux kernel mirror (for testing)
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1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * i2c-smbus.c - SMBus extensions to the I2C protocol
4 *
5 * Copyright (C) 2008 David Brownell
6 * Copyright (C) 2010 Jean Delvare <jdelvare@suse.de>
7 */
8
9#include <linux/device.h>
10#include <linux/i2c.h>
11#include <linux/i2c-smbus.h>
12#include <linux/interrupt.h>
13#include <linux/kernel.h>
14#include <linux/module.h>
15#include <linux/of_irq.h>
16#include <linux/slab.h>
17#include <linux/workqueue.h>
18
19struct i2c_smbus_alert {
20 struct work_struct alert;
21 struct i2c_client *ara; /* Alert response address */
22};
23
24struct alert_data {
25 unsigned short addr;
26 enum i2c_alert_protocol type;
27 unsigned int data;
28};
29
30/* If this is the alerting device, notify its driver */
31static int smbus_do_alert(struct device *dev, void *addrp)
32{
33 struct i2c_client *client = i2c_verify_client(dev);
34 struct alert_data *data = addrp;
35 struct i2c_driver *driver;
36
37 if (!client || client->addr != data->addr)
38 return 0;
39 if (client->flags & I2C_CLIENT_TEN)
40 return 0;
41
42 /*
43 * Drivers should either disable alerts, or provide at least
44 * a minimal handler. Lock so the driver won't change.
45 */
46 device_lock(dev);
47 if (client->dev.driver) {
48 driver = to_i2c_driver(client->dev.driver);
49 if (driver->alert)
50 driver->alert(client, data->type, data->data);
51 else
52 dev_warn(&client->dev, "no driver alert()!\n");
53 } else
54 dev_dbg(&client->dev, "alert with no driver\n");
55 device_unlock(dev);
56
57 /* Stop iterating after we find the device */
58 return -EBUSY;
59}
60
61/*
62 * The alert IRQ handler needs to hand work off to a task which can issue
63 * SMBus calls, because those sleeping calls can't be made in IRQ context.
64 */
65static irqreturn_t smbus_alert(int irq, void *d)
66{
67 struct i2c_smbus_alert *alert = d;
68 struct i2c_client *ara;
69 unsigned short prev_addr = 0; /* Not a valid address */
70
71 ara = alert->ara;
72
73 for (;;) {
74 s32 status;
75 struct alert_data data;
76
77 /*
78 * Devices with pending alerts reply in address order, low
79 * to high, because of slave transmit arbitration. After
80 * responding, an SMBus device stops asserting SMBALERT#.
81 *
82 * Note that SMBus 2.0 reserves 10-bit addresses for future
83 * use. We neither handle them, nor try to use PEC here.
84 */
85 status = i2c_smbus_read_byte(ara);
86 if (status < 0)
87 break;
88
89 data.data = status & 1;
90 data.addr = status >> 1;
91 data.type = I2C_PROTOCOL_SMBUS_ALERT;
92
93 if (data.addr == prev_addr) {
94 dev_warn(&ara->dev, "Duplicate SMBALERT# from dev "
95 "0x%02x, skipping\n", data.addr);
96 break;
97 }
98 dev_dbg(&ara->dev, "SMBALERT# from dev 0x%02x, flag %d\n",
99 data.addr, data.data);
100
101 /* Notify driver for the device which issued the alert */
102 device_for_each_child(&ara->adapter->dev, &data,
103 smbus_do_alert);
104 prev_addr = data.addr;
105 }
106
107 return IRQ_HANDLED;
108}
109
110static void smbalert_work(struct work_struct *work)
111{
112 struct i2c_smbus_alert *alert;
113
114 alert = container_of(work, struct i2c_smbus_alert, alert);
115
116 smbus_alert(0, alert);
117
118}
119
120/* Setup SMBALERT# infrastructure */
121static int smbalert_probe(struct i2c_client *ara,
122 const struct i2c_device_id *id)
123{
124 struct i2c_smbus_alert_setup *setup = dev_get_platdata(&ara->dev);
125 struct i2c_smbus_alert *alert;
126 struct i2c_adapter *adapter = ara->adapter;
127 int res, irq;
128
129 alert = devm_kzalloc(&ara->dev, sizeof(struct i2c_smbus_alert),
130 GFP_KERNEL);
131 if (!alert)
132 return -ENOMEM;
133
134 if (setup) {
135 irq = setup->irq;
136 } else {
137 irq = of_irq_get_byname(adapter->dev.of_node, "smbus_alert");
138 if (irq <= 0)
139 return irq;
140 }
141
142 INIT_WORK(&alert->alert, smbalert_work);
143 alert->ara = ara;
144
145 if (irq > 0) {
146 res = devm_request_threaded_irq(&ara->dev, irq,
147 NULL, smbus_alert,
148 IRQF_SHARED | IRQF_ONESHOT,
149 "smbus_alert", alert);
150 if (res)
151 return res;
152 }
153
154 i2c_set_clientdata(ara, alert);
155 dev_info(&adapter->dev, "supports SMBALERT#\n");
156
157 return 0;
158}
159
160/* IRQ and memory resources are managed so they are freed automatically */
161static int smbalert_remove(struct i2c_client *ara)
162{
163 struct i2c_smbus_alert *alert = i2c_get_clientdata(ara);
164
165 cancel_work_sync(&alert->alert);
166 return 0;
167}
168
169static const struct i2c_device_id smbalert_ids[] = {
170 { "smbus_alert", 0 },
171 { /* LIST END */ }
172};
173MODULE_DEVICE_TABLE(i2c, smbalert_ids);
174
175static struct i2c_driver smbalert_driver = {
176 .driver = {
177 .name = "smbus_alert",
178 },
179 .probe = smbalert_probe,
180 .remove = smbalert_remove,
181 .id_table = smbalert_ids,
182};
183
184/**
185 * i2c_handle_smbus_alert - Handle an SMBus alert
186 * @ara: the ARA client on the relevant adapter
187 * Context: can't sleep
188 *
189 * Helper function to be called from an I2C bus driver's interrupt
190 * handler. It will schedule the alert work, in turn calling the
191 * corresponding I2C device driver's alert function.
192 *
193 * It is assumed that ara is a valid i2c client previously returned by
194 * i2c_setup_smbus_alert().
195 */
196int i2c_handle_smbus_alert(struct i2c_client *ara)
197{
198 struct i2c_smbus_alert *alert = i2c_get_clientdata(ara);
199
200 return schedule_work(&alert->alert);
201}
202EXPORT_SYMBOL_GPL(i2c_handle_smbus_alert);
203
204module_i2c_driver(smbalert_driver);
205
206MODULE_AUTHOR("Jean Delvare <jdelvare@suse.de>");
207MODULE_DESCRIPTION("SMBus protocol extensions support");
208MODULE_LICENSE("GPL");