tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
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
70 ara = alert->ara;
71
72 for (;;) {
73 s32 status;
74 struct alert_data data;
75
76 /*
77 * Devices with pending alerts reply in address order, low
78 * to high, because of slave transmit arbitration. After
79 * responding, an SMBus device stops asserting SMBALERT#.
80 *
81 * Note that SMBus 2.0 reserves 10-bit addresses for future
82 * use. We neither handle them, nor try to use PEC here.
83 */
84 status = i2c_smbus_read_byte(ara);
85 if (status < 0)
86 break;
87
88 data.data = status & 1;
89 data.addr = status >> 1;
90 data.type = I2C_PROTOCOL_SMBUS_ALERT;
91
92 dev_dbg(&ara->dev, "SMBALERT# from dev 0x%02x, flag %d\n",
93 data.addr, data.data);
94
95 /* Notify driver for the device which issued the alert */
96 device_for_each_child(&ara->adapter->dev, &data,
97 smbus_do_alert);
98 }
99
100 return IRQ_HANDLED;
101}
102
103static void smbalert_work(struct work_struct *work)
104{
105 struct i2c_smbus_alert *alert;
106
107 alert = container_of(work, struct i2c_smbus_alert, alert);
108
109 smbus_alert(0, alert);
110
111}
112
113/* Setup SMBALERT# infrastructure */
114static int smbalert_probe(struct i2c_client *ara,
115 const struct i2c_device_id *id)
116{
117 struct i2c_smbus_alert_setup *setup = dev_get_platdata(&ara->dev);
118 struct i2c_smbus_alert *alert;
119 struct i2c_adapter *adapter = ara->adapter;
120 int res, irq;
121
122 alert = devm_kzalloc(&ara->dev, sizeof(struct i2c_smbus_alert),
123 GFP_KERNEL);
124 if (!alert)
125 return -ENOMEM;
126
127 if (setup) {
128 irq = setup->irq;
129 } else {
130 irq = of_irq_get_byname(adapter->dev.of_node, "smbus_alert");
131 if (irq <= 0)
132 return irq;
133 }
134
135 INIT_WORK(&alert->alert, smbalert_work);
136 alert->ara = ara;
137
138 if (irq > 0) {
139 res = devm_request_threaded_irq(&ara->dev, irq,
140 NULL, smbus_alert,
141 IRQF_SHARED | IRQF_ONESHOT,
142 "smbus_alert", alert);
143 if (res)
144 return res;
145 }
146
147 i2c_set_clientdata(ara, alert);
148 dev_info(&adapter->dev, "supports SMBALERT#\n");
149
150 return 0;
151}
152
153/* IRQ and memory resources are managed so they are freed automatically */
154static int smbalert_remove(struct i2c_client *ara)
155{
156 struct i2c_smbus_alert *alert = i2c_get_clientdata(ara);
157
158 cancel_work_sync(&alert->alert);
159 return 0;
160}
161
162static const struct i2c_device_id smbalert_ids[] = {
163 { "smbus_alert", 0 },
164 { /* LIST END */ }
165};
166MODULE_DEVICE_TABLE(i2c, smbalert_ids);
167
168static struct i2c_driver smbalert_driver = {
169 .driver = {
170 .name = "smbus_alert",
171 },
172 .probe = smbalert_probe,
173 .remove = smbalert_remove,
174 .id_table = smbalert_ids,
175};
176
177/**
178 * i2c_handle_smbus_alert - Handle an SMBus alert
179 * @ara: the ARA client on the relevant adapter
180 * Context: can't sleep
181 *
182 * Helper function to be called from an I2C bus driver's interrupt
183 * handler. It will schedule the alert work, in turn calling the
184 * corresponding I2C device driver's alert function.
185 *
186 * It is assumed that ara is a valid i2c client previously returned by
187 * i2c_new_smbus_alert_device().
188 */
189int i2c_handle_smbus_alert(struct i2c_client *ara)
190{
191 struct i2c_smbus_alert *alert = i2c_get_clientdata(ara);
192
193 return schedule_work(&alert->alert);
194}
195EXPORT_SYMBOL_GPL(i2c_handle_smbus_alert);
196
197module_i2c_driver(smbalert_driver);
198
199MODULE_AUTHOR("Jean Delvare <jdelvare@suse.de>");
200MODULE_DESCRIPTION("SMBus protocol extensions support");
201MODULE_LICENSE("GPL");