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b5527a77 JD |
1 | /* |
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 | |
5694f8a8 JD |
19 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, |
20 | * MA 02110-1301 USA. | |
b5527a77 JD |
21 | */ |
22 | ||
23 | #include <linux/kernel.h> | |
24 | #include <linux/module.h> | |
25 | #include <linux/device.h> | |
b5527a77 JD |
26 | #include <linux/interrupt.h> |
27 | #include <linux/workqueue.h> | |
28 | #include <linux/i2c.h> | |
29 | #include <linux/i2c-smbus.h> | |
5a0e3ad6 | 30 | #include <linux/slab.h> |
b5527a77 JD |
31 | |
32 | struct 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 | ||
39 | struct alert_data { | |
40 | unsigned short addr; | |
41 | u8 flag:1; | |
42 | }; | |
43 | ||
44 | /* If this is the alerting device, notify its driver */ | |
45 | static 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 | */ | |
f635a1e7 | 59 | device_lock(dev); |
b5527a77 JD |
60 | 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"); | |
f635a1e7 | 67 | device_unlock(dev); |
b5527a77 JD |
68 | |
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 | */ | |
77 | static 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 | ||
124 | static 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 */ | |
137 | static 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 | ||
145 | alert = kzalloc(sizeof(struct i2c_smbus_alert), GFP_KERNEL); | |
146 | if (!alert) | |
147 | return -ENOMEM; | |
148 | ||
149 | alert->alert_edge_triggered = setup->alert_edge_triggered; | |
150 | alert->irq = setup->irq; | |
151 | INIT_WORK(&alert->alert, smbus_alert); | |
152 | alert->ara = ara; | |
153 | ||
154 | if (setup->irq > 0) { | |
155 | res = devm_request_irq(&ara->dev, setup->irq, smbalert_irq, | |
156 | 0, "smbus_alert", alert); | |
157 | if (res) { | |
158 | kfree(alert); | |
159 | return res; | |
160 | } | |
161 | } | |
162 | ||
163 | i2c_set_clientdata(ara, alert); | |
164 | dev_info(&adapter->dev, "supports SMBALERT#, %s trigger\n", | |
165 | setup->alert_edge_triggered ? "edge" : "level"); | |
166 | ||
167 | return 0; | |
168 | } | |
169 | ||
170 | /* IRQ resource is managed so it is freed automatically */ | |
171 | static int smbalert_remove(struct i2c_client *ara) | |
172 | { | |
173 | struct i2c_smbus_alert *alert = i2c_get_clientdata(ara); | |
174 | ||
175 | cancel_work_sync(&alert->alert); | |
176 | ||
b5527a77 JD |
177 | kfree(alert); |
178 | return 0; | |
179 | } | |
180 | ||
181 | static const struct i2c_device_id smbalert_ids[] = { | |
182 | { "smbus_alert", 0 }, | |
183 | { /* LIST END */ } | |
184 | }; | |
185 | MODULE_DEVICE_TABLE(i2c, smbalert_ids); | |
186 | ||
187 | static struct i2c_driver smbalert_driver = { | |
188 | .driver = { | |
189 | .name = "smbus_alert", | |
190 | }, | |
191 | .probe = smbalert_probe, | |
192 | .remove = smbalert_remove, | |
193 | .id_table = smbalert_ids, | |
194 | }; | |
195 | ||
196 | /** | |
197 | * i2c_setup_smbus_alert - Setup SMBus alert support | |
198 | * @adapter: the target adapter | |
199 | * @setup: setup data for the SMBus alert handler | |
200 | * Context: can sleep | |
201 | * | |
202 | * Setup handling of the SMBus alert protocol on a given I2C bus segment. | |
203 | * | |
204 | * Handling can be done either through our IRQ handler, or by the | |
205 | * adapter (from its handler, periodic polling, or whatever). | |
206 | * | |
207 | * NOTE that if we manage the IRQ, we *MUST* know if it's level or | |
208 | * edge triggered in order to hand it to the workqueue correctly. | |
209 | * If triggering the alert seems to wedge the system, you probably | |
210 | * should have said it's level triggered. | |
211 | * | |
212 | * This returns the ara client, which should be saved for later use with | |
213 | * i2c_handle_smbus_alert() and ultimately i2c_unregister_device(); or NULL | |
214 | * to indicate an error. | |
215 | */ | |
216 | struct i2c_client *i2c_setup_smbus_alert(struct i2c_adapter *adapter, | |
217 | struct i2c_smbus_alert_setup *setup) | |
218 | { | |
219 | struct i2c_board_info ara_board_info = { | |
220 | I2C_BOARD_INFO("smbus_alert", 0x0c), | |
221 | .platform_data = setup, | |
222 | }; | |
223 | ||
224 | return i2c_new_device(adapter, &ara_board_info); | |
225 | } | |
226 | EXPORT_SYMBOL_GPL(i2c_setup_smbus_alert); | |
227 | ||
228 | /** | |
229 | * i2c_handle_smbus_alert - Handle an SMBus alert | |
230 | * @ara: the ARA client on the relevant adapter | |
231 | * Context: can't sleep | |
232 | * | |
233 | * Helper function to be called from an I2C bus driver's interrupt | |
234 | * handler. It will schedule the alert work, in turn calling the | |
235 | * corresponding I2C device driver's alert function. | |
236 | * | |
237 | * It is assumed that ara is a valid i2c client previously returned by | |
238 | * i2c_setup_smbus_alert(). | |
239 | */ | |
240 | int i2c_handle_smbus_alert(struct i2c_client *ara) | |
241 | { | |
242 | struct i2c_smbus_alert *alert = i2c_get_clientdata(ara); | |
243 | ||
244 | return schedule_work(&alert->alert); | |
245 | } | |
246 | EXPORT_SYMBOL_GPL(i2c_handle_smbus_alert); | |
247 | ||
248 | static int __init i2c_smbus_init(void) | |
249 | { | |
250 | return i2c_add_driver(&smbalert_driver); | |
251 | } | |
252 | ||
253 | static void __exit i2c_smbus_exit(void) | |
254 | { | |
255 | i2c_del_driver(&smbalert_driver); | |
256 | } | |
257 | ||
258 | module_init(i2c_smbus_init); | |
259 | module_exit(i2c_smbus_exit); | |
260 | ||
261 | MODULE_AUTHOR("Jean Delvare <khali@linux-fr.org>"); | |
262 | MODULE_DESCRIPTION("SMBus protocol extensions support"); | |
263 | MODULE_LICENSE("GPL"); |