1/*
2 * i2c-smbus.c - SMBus extensions to the I2C protocol
3 *
4 * Copyright (C) 2008 David Brownell
5 * Copyright (C) 2010 Jean Delvare <jdelvare@suse.de>
6 *
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License as published by
9 * the Free Software Foundation; either version 2 of the License, or
10 * (at your option) any later version.
11 *
12 * This program is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 * GNU General Public License for more details.
16 */
17
18#include <linux/device.h>
19#include <linux/i2c.h>
20#include <linux/i2c-smbus.h>
21#include <linux/interrupt.h>
22#include <linux/kernel.h>
23#include <linux/module.h>
24#include <linux/of_irq.h>
25#include <linux/slab.h>
26#include <linux/workqueue.h>
27
28struct i2c_smbus_alert {
29 struct work_struct alert;
30 struct i2c_client *ara; /* Alert response address */
31};
32
33struct alert_data {
34 unsigned short addr;
35 enum i2c_alert_protocol type;
36 unsigned int data;
37};
38
39/* If this is the alerting device, notify its driver */
40static int smbus_do_alert(struct device *dev, void *addrp)
41{
42 struct i2c_client *client = i2c_verify_client(dev);
43 struct alert_data *data = addrp;
44 struct i2c_driver *driver;
45
46 if (!client || client->addr != data->addr)
47 return 0;
48 if (client->flags & I2C_CLIENT_TEN)
49 return 0;
50
51 /*
52 * Drivers should either disable alerts, or provide at least
53 * a minimal handler. Lock so the driver won't change.
54 */
55 device_lock(dev);
56 if (client->dev.driver) {
57 driver = to_i2c_driver(client->dev.driver);
58 if (driver->alert)
59 driver->alert(client, data->type, data->data);
60 else
61 dev_warn(&client->dev, "no driver alert()!\n");
62 } else
63 dev_dbg(&client->dev, "alert with no driver\n");
64 device_unlock(dev);
65
66 /* Stop iterating after we find the device */
67 return -EBUSY;
68}
69
70/*
71 * The alert IRQ handler needs to hand work off to a task which can issue
72 * SMBus calls, because those sleeping calls can't be made in IRQ context.
73 */
74static irqreturn_t smbus_alert(int irq, void *d)
75{
76 struct i2c_smbus_alert *alert = d;
77 struct i2c_client *ara;
78 unsigned short prev_addr = 0; /* Not a valid address */
79
80 ara = alert->ara;
81
82 for (;;) {
83 s32 status;
84 struct alert_data data;
85
86 /*
87 * Devices with pending alerts reply in address order, low
88 * to high, because of slave transmit arbitration. After
89 * responding, an SMBus device stops asserting SMBALERT#.
90 *
91 * Note that SMBus 2.0 reserves 10-bit addresses for future
92 * use. We neither handle them, nor try to use PEC here.
93 */
94 status = i2c_smbus_read_byte(ara);
95 if (status < 0)
96 break;
97
98 data.data = status & 1;
99 data.addr = status >> 1;
100 data.type = I2C_PROTOCOL_SMBUS_ALERT;
101
102 if (data.addr == prev_addr) {
103 dev_warn(&ara->dev, "Duplicate SMBALERT# from dev "
104 "0x%02x, skipping\n", data.addr);
105 break;
106 }
107 dev_dbg(&ara->dev, "SMBALERT# from dev 0x%02x, flag %d\n",
108 data.addr, data.data);
109
110 /* Notify driver for the device which issued the alert */
111 device_for_each_child(&ara->adapter->dev, &data,
112 smbus_do_alert);
113 prev_addr = data.addr;
114 }
115
116 return IRQ_HANDLED;
117}
118
119static void smbalert_work(struct work_struct *work)
120{
121 struct i2c_smbus_alert *alert;
122
123 alert = container_of(work, struct i2c_smbus_alert, alert);
124
125 smbus_alert(0, alert);
126
127}
128
129/* Setup SMBALERT# infrastructure */
130static int smbalert_probe(struct i2c_client *ara,
131 const struct i2c_device_id *id)
132{
133 struct i2c_smbus_alert_setup *setup = dev_get_platdata(&ara->dev);
134 struct i2c_smbus_alert *alert;
135 struct i2c_adapter *adapter = ara->adapter;
136 int res, irq;
137
138 alert = devm_kzalloc(&ara->dev, sizeof(struct i2c_smbus_alert),
139 GFP_KERNEL);
140 if (!alert)
141 return -ENOMEM;
142
143 if (setup) {
144 irq = setup->irq;
145 } else {
146 irq = of_irq_get_byname(adapter->dev.of_node, "smbus_alert");
147 if (irq <= 0)
148 return irq;
149 }
150
151 INIT_WORK(&alert->alert, smbalert_work);
152 alert->ara = ara;
153
154 if (irq > 0) {
155 res = devm_request_threaded_irq(&ara->dev, irq,
156 NULL, smbus_alert,
157 IRQF_SHARED | IRQF_ONESHOT,
158 "smbus_alert", alert);
159 if (res)
160 return res;
161 }
162
163 i2c_set_clientdata(ara, alert);
164 dev_info(&adapter->dev, "supports SMBALERT#\n");
165
166 return 0;
167}
168
169/* IRQ and memory resources are managed so they are freed automatically */
170static int smbalert_remove(struct i2c_client *ara)
171{
172 struct i2c_smbus_alert *alert = i2c_get_clientdata(ara);
173
174 cancel_work_sync(&alert->alert);
175 return 0;
176}
177
178static const struct i2c_device_id smbalert_ids[] = {
179 { "smbus_alert", 0 },
180 { /* LIST END */ }
181};
182MODULE_DEVICE_TABLE(i2c, smbalert_ids);
183
184static struct i2c_driver smbalert_driver = {
185 .driver = {
186 .name = "smbus_alert",
187 },
188 .probe = smbalert_probe,
189 .remove = smbalert_remove,
190 .id_table = smbalert_ids,
191};
192
193/**
194 * i2c_handle_smbus_alert - Handle an SMBus alert
195 * @ara: the ARA client on the relevant adapter
196 * Context: can't sleep
197 *
198 * Helper function to be called from an I2C bus driver's interrupt
199 * handler. It will schedule the alert work, in turn calling the
200 * corresponding I2C device driver's alert function.
201 *
202 * It is assumed that ara is a valid i2c client previously returned by
203 * i2c_setup_smbus_alert().
204 */
205int i2c_handle_smbus_alert(struct i2c_client *ara)
206{
207 struct i2c_smbus_alert *alert = i2c_get_clientdata(ara);
208
209 return schedule_work(&alert->alert);
210}
211EXPORT_SYMBOL_GPL(i2c_handle_smbus_alert);
212
213module_i2c_driver(smbalert_driver);
214
215MODULE_AUTHOR("Jean Delvare <jdelvare@suse.de>");
216MODULE_DESCRIPTION("SMBus protocol extensions support");
217MODULE_LICENSE("GPL");
218