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Jean Delvareb5527a72010-03-02 12:23:42 +01001/*
2 * i2c-smbus.c - SMBus extensions to the I2C protocol
3 *
4 * Copyright (C) 2008 David Brownell
5 * Copyright (C) 2010 Jean Delvare <khali@linux-fr.org>
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 * You should have received a copy of the GNU General Public License
18 * along with this program; if not, write to the Free Software
Jean Delvare5694f8a2012-03-26 21:47:19 +020019 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
20 * MA 02110-1301 USA.
Jean Delvareb5527a72010-03-02 12:23:42 +010021 */
22
23#include <linux/kernel.h>
24#include <linux/module.h>
25#include <linux/device.h>
Jean Delvareb5527a72010-03-02 12:23:42 +010026#include <linux/interrupt.h>
27#include <linux/workqueue.h>
28#include <linux/i2c.h>
29#include <linux/i2c-smbus.h>
Tejun Heo5a0e3ad2010-03-24 17:04:11 +090030#include <linux/slab.h>
Jean Delvareb5527a72010-03-02 12:23:42 +010031
32struct i2c_smbus_alert {
33 unsigned int alert_edge_triggered:1;
34 int irq;
35 struct work_struct alert;
36 struct i2c_client *ara; /* Alert response address */
37};
38
39struct alert_data {
40 unsigned short addr;
41 u8 flag:1;
42};
43
44/* If this is the alerting device, notify its driver */
45static int smbus_do_alert(struct device *dev, void *addrp)
46{
47 struct i2c_client *client = i2c_verify_client(dev);
48 struct alert_data *data = addrp;
49
50 if (!client || client->addr != data->addr)
51 return 0;
52 if (client->flags & I2C_CLIENT_TEN)
53 return 0;
54
55 /*
56 * Drivers should either disable alerts, or provide at least
57 * a minimal handler. Lock so client->driver won't change.
58 */
Stephen Rothwellf635a1e2010-03-01 16:04:45 +110059 device_lock(dev);
Jean Delvareb5527a72010-03-02 12:23:42 +010060 if (client->driver) {
61 if (client->driver->alert)
62 client->driver->alert(client, data->flag);
63 else
64 dev_warn(&client->dev, "no driver alert()!\n");
65 } else
66 dev_dbg(&client->dev, "alert with no driver\n");
Stephen Rothwellf635a1e2010-03-01 16:04:45 +110067 device_unlock(dev);
Jean Delvareb5527a72010-03-02 12:23:42 +010068
69 /* Stop iterating after we find the device */
70 return -EBUSY;
71}
72
73/*
74 * The alert IRQ handler needs to hand work off to a task which can issue
75 * SMBus calls, because those sleeping calls can't be made in IRQ context.
76 */
77static void smbus_alert(struct work_struct *work)
78{
79 struct i2c_smbus_alert *alert;
80 struct i2c_client *ara;
81 unsigned short prev_addr = 0; /* Not a valid address */
82
83 alert = container_of(work, struct i2c_smbus_alert, alert);
84 ara = alert->ara;
85
86 for (;;) {
87 s32 status;
88 struct alert_data data;
89
90 /*
91 * Devices with pending alerts reply in address order, low
92 * to high, because of slave transmit arbitration. After
93 * responding, an SMBus device stops asserting SMBALERT#.
94 *
95 * Note that SMBus 2.0 reserves 10-bit addresess for future
96 * use. We neither handle them, nor try to use PEC here.
97 */
98 status = i2c_smbus_read_byte(ara);
99 if (status < 0)
100 break;
101
102 data.flag = status & 1;
103 data.addr = status >> 1;
104
105 if (data.addr == prev_addr) {
106 dev_warn(&ara->dev, "Duplicate SMBALERT# from dev "
107 "0x%02x, skipping\n", data.addr);
108 break;
109 }
110 dev_dbg(&ara->dev, "SMBALERT# from dev 0x%02x, flag %d\n",
111 data.addr, data.flag);
112
113 /* Notify driver for the device which issued the alert */
114 device_for_each_child(&ara->adapter->dev, &data,
115 smbus_do_alert);
116 prev_addr = data.addr;
117 }
118
119 /* We handled all alerts; re-enable level-triggered IRQs */
120 if (!alert->alert_edge_triggered)
121 enable_irq(alert->irq);
122}
123
124static irqreturn_t smbalert_irq(int irq, void *d)
125{
126 struct i2c_smbus_alert *alert = d;
127
128 /* Disable level-triggered IRQs until we handle them */
129 if (!alert->alert_edge_triggered)
130 disable_irq_nosync(irq);
131
132 schedule_work(&alert->alert);
133 return IRQ_HANDLED;
134}
135
136/* Setup SMBALERT# infrastructure */
137static int smbalert_probe(struct i2c_client *ara,
138 const struct i2c_device_id *id)
139{
140 struct i2c_smbus_alert_setup *setup = ara->dev.platform_data;
141 struct i2c_smbus_alert *alert;
142 struct i2c_adapter *adapter = ara->adapter;
143 int res;
144
Julia Lawall71b57842012-10-05 22:23:52 +0200145 alert = devm_kzalloc(&ara->dev, sizeof(struct i2c_smbus_alert),
146 GFP_KERNEL);
Jean Delvareb5527a72010-03-02 12:23:42 +0100147 if (!alert)
148 return -ENOMEM;
149
150 alert->alert_edge_triggered = setup->alert_edge_triggered;
151 alert->irq = setup->irq;
152 INIT_WORK(&alert->alert, smbus_alert);
153 alert->ara = ara;
154
155 if (setup->irq > 0) {
156 res = devm_request_irq(&ara->dev, setup->irq, smbalert_irq,
157 0, "smbus_alert", alert);
Julia Lawall71b57842012-10-05 22:23:52 +0200158 if (res)
Jean Delvareb5527a72010-03-02 12:23:42 +0100159 return res;
Jean Delvareb5527a72010-03-02 12:23:42 +0100160 }
161
162 i2c_set_clientdata(ara, alert);
163 dev_info(&adapter->dev, "supports SMBALERT#, %s trigger\n",
164 setup->alert_edge_triggered ? "edge" : "level");
165
166 return 0;
167}
168
Julia Lawall71b57842012-10-05 22:23:52 +0200169/* IRQ and memory resources are managed so they are freed automatically */
Jean Delvareb5527a72010-03-02 12:23:42 +0100170static 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);
Jean Delvareb5527a72010-03-02 12:23:42 +0100175 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_setup_smbus_alert - Setup SMBus alert support
195 * @adapter: the target adapter
196 * @setup: setup data for the SMBus alert handler
197 * Context: can sleep
198 *
199 * Setup handling of the SMBus alert protocol on a given I2C bus segment.
200 *
201 * Handling can be done either through our IRQ handler, or by the
202 * adapter (from its handler, periodic polling, or whatever).
203 *
204 * NOTE that if we manage the IRQ, we *MUST* know if it's level or
205 * edge triggered in order to hand it to the workqueue correctly.
206 * If triggering the alert seems to wedge the system, you probably
207 * should have said it's level triggered.
208 *
209 * This returns the ara client, which should be saved for later use with
210 * i2c_handle_smbus_alert() and ultimately i2c_unregister_device(); or NULL
211 * to indicate an error.
212 */
213struct i2c_client *i2c_setup_smbus_alert(struct i2c_adapter *adapter,
214 struct i2c_smbus_alert_setup *setup)
215{
216 struct i2c_board_info ara_board_info = {
217 I2C_BOARD_INFO("smbus_alert", 0x0c),
218 .platform_data = setup,
219 };
220
221 return i2c_new_device(adapter, &ara_board_info);
222}
223EXPORT_SYMBOL_GPL(i2c_setup_smbus_alert);
224
225/**
226 * i2c_handle_smbus_alert - Handle an SMBus alert
227 * @ara: the ARA client on the relevant adapter
228 * Context: can't sleep
229 *
230 * Helper function to be called from an I2C bus driver's interrupt
231 * handler. It will schedule the alert work, in turn calling the
232 * corresponding I2C device driver's alert function.
233 *
234 * It is assumed that ara is a valid i2c client previously returned by
235 * i2c_setup_smbus_alert().
236 */
237int i2c_handle_smbus_alert(struct i2c_client *ara)
238{
239 struct i2c_smbus_alert *alert = i2c_get_clientdata(ara);
240
241 return schedule_work(&alert->alert);
242}
243EXPORT_SYMBOL_GPL(i2c_handle_smbus_alert);
244
Fabio Estevamfda2f4a2012-07-24 14:13:57 +0200245module_i2c_driver(smbalert_driver);
Jean Delvareb5527a72010-03-02 12:23:42 +0100246
247MODULE_AUTHOR("Jean Delvare <khali@linux-fr.org>");
248MODULE_DESCRIPTION("SMBus protocol extensions support");
249MODULE_LICENSE("GPL");