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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 | |
19 | * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. | |
20 | */ | |
21 | ||
22 | #include <linux/kernel.h> | |
23 | #include <linux/module.h> | |
24 | #include <linux/device.h> | |
b5527a77 JD |
25 | #include <linux/interrupt.h> |
26 | #include <linux/workqueue.h> | |
27 | #include <linux/i2c.h> | |
28 | #include <linux/i2c-smbus.h> | |
5a0e3ad6 | 29 | #include <linux/slab.h> |
b5527a77 JD |
30 | |
31 | struct i2c_smbus_alert { | |
32 | unsigned int alert_edge_triggered:1; | |
33 | int irq; | |
34 | struct work_struct alert; | |
35 | struct i2c_client *ara; /* Alert response address */ | |
36 | }; | |
37 | ||
38 | struct alert_data { | |
39 | unsigned short addr; | |
40 | u8 flag:1; | |
41 | }; | |
42 | ||
43 | /* If this is the alerting device, notify its driver */ | |
44 | static int smbus_do_alert(struct device *dev, void *addrp) | |
45 | { | |
46 | struct i2c_client *client = i2c_verify_client(dev); | |
47 | struct alert_data *data = addrp; | |
48 | ||
49 | if (!client || client->addr != data->addr) | |
50 | return 0; | |
51 | if (client->flags & I2C_CLIENT_TEN) | |
52 | return 0; | |
53 | ||
54 | /* | |
55 | * Drivers should either disable alerts, or provide at least | |
56 | * a minimal handler. Lock so client->driver won't change. | |
57 | */ | |
f635a1e7 | 58 | device_lock(dev); |
b5527a77 JD |
59 | if (client->driver) { |
60 | if (client->driver->alert) | |
61 | client->driver->alert(client, data->flag); | |
62 | else | |
63 | dev_warn(&client->dev, "no driver alert()!\n"); | |
64 | } else | |
65 | dev_dbg(&client->dev, "alert with no driver\n"); | |
f635a1e7 | 66 | device_unlock(dev); |
b5527a77 JD |
67 | |
68 | /* Stop iterating after we find the device */ | |
69 | return -EBUSY; | |
70 | } | |
71 | ||
72 | /* | |
73 | * The alert IRQ handler needs to hand work off to a task which can issue | |
74 | * SMBus calls, because those sleeping calls can't be made in IRQ context. | |
75 | */ | |
76 | static void smbus_alert(struct work_struct *work) | |
77 | { | |
78 | struct i2c_smbus_alert *alert; | |
79 | struct i2c_client *ara; | |
80 | unsigned short prev_addr = 0; /* Not a valid address */ | |
81 | ||
82 | alert = container_of(work, struct i2c_smbus_alert, alert); | |
83 | ara = alert->ara; | |
84 | ||
85 | for (;;) { | |
86 | s32 status; | |
87 | struct alert_data data; | |
88 | ||
89 | /* | |
90 | * Devices with pending alerts reply in address order, low | |
91 | * to high, because of slave transmit arbitration. After | |
92 | * responding, an SMBus device stops asserting SMBALERT#. | |
93 | * | |
94 | * Note that SMBus 2.0 reserves 10-bit addresess for future | |
95 | * use. We neither handle them, nor try to use PEC here. | |
96 | */ | |
97 | status = i2c_smbus_read_byte(ara); | |
98 | if (status < 0) | |
99 | break; | |
100 | ||
101 | data.flag = status & 1; | |
102 | data.addr = status >> 1; | |
103 | ||
104 | if (data.addr == prev_addr) { | |
105 | dev_warn(&ara->dev, "Duplicate SMBALERT# from dev " | |
106 | "0x%02x, skipping\n", data.addr); | |
107 | break; | |
108 | } | |
109 | dev_dbg(&ara->dev, "SMBALERT# from dev 0x%02x, flag %d\n", | |
110 | data.addr, data.flag); | |
111 | ||
112 | /* Notify driver for the device which issued the alert */ | |
113 | device_for_each_child(&ara->adapter->dev, &data, | |
114 | smbus_do_alert); | |
115 | prev_addr = data.addr; | |
116 | } | |
117 | ||
118 | /* We handled all alerts; re-enable level-triggered IRQs */ | |
119 | if (!alert->alert_edge_triggered) | |
120 | enable_irq(alert->irq); | |
121 | } | |
122 | ||
123 | static irqreturn_t smbalert_irq(int irq, void *d) | |
124 | { | |
125 | struct i2c_smbus_alert *alert = d; | |
126 | ||
127 | /* Disable level-triggered IRQs until we handle them */ | |
128 | if (!alert->alert_edge_triggered) | |
129 | disable_irq_nosync(irq); | |
130 | ||
131 | schedule_work(&alert->alert); | |
132 | return IRQ_HANDLED; | |
133 | } | |
134 | ||
135 | /* Setup SMBALERT# infrastructure */ | |
136 | static int smbalert_probe(struct i2c_client *ara, | |
137 | const struct i2c_device_id *id) | |
138 | { | |
139 | struct i2c_smbus_alert_setup *setup = ara->dev.platform_data; | |
140 | struct i2c_smbus_alert *alert; | |
141 | struct i2c_adapter *adapter = ara->adapter; | |
142 | int res; | |
143 | ||
144 | alert = kzalloc(sizeof(struct i2c_smbus_alert), GFP_KERNEL); | |
145 | if (!alert) | |
146 | return -ENOMEM; | |
147 | ||
148 | alert->alert_edge_triggered = setup->alert_edge_triggered; | |
149 | alert->irq = setup->irq; | |
150 | INIT_WORK(&alert->alert, smbus_alert); | |
151 | alert->ara = ara; | |
152 | ||
153 | if (setup->irq > 0) { | |
154 | res = devm_request_irq(&ara->dev, setup->irq, smbalert_irq, | |
155 | 0, "smbus_alert", alert); | |
156 | if (res) { | |
157 | kfree(alert); | |
158 | return res; | |
159 | } | |
160 | } | |
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 | ||
169 | /* IRQ resource is managed so it is freed automatically */ | |
170 | static 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 | ||
b5527a77 JD |
176 | kfree(alert); |
177 | return 0; | |
178 | } | |
179 | ||
180 | static const struct i2c_device_id smbalert_ids[] = { | |
181 | { "smbus_alert", 0 }, | |
182 | { /* LIST END */ } | |
183 | }; | |
184 | MODULE_DEVICE_TABLE(i2c, smbalert_ids); | |
185 | ||
186 | static struct i2c_driver smbalert_driver = { | |
187 | .driver = { | |
188 | .name = "smbus_alert", | |
189 | }, | |
190 | .probe = smbalert_probe, | |
191 | .remove = smbalert_remove, | |
192 | .id_table = smbalert_ids, | |
193 | }; | |
194 | ||
195 | /** | |
196 | * i2c_setup_smbus_alert - Setup SMBus alert support | |
197 | * @adapter: the target adapter | |
198 | * @setup: setup data for the SMBus alert handler | |
199 | * Context: can sleep | |
200 | * | |
201 | * Setup handling of the SMBus alert protocol on a given I2C bus segment. | |
202 | * | |
203 | * Handling can be done either through our IRQ handler, or by the | |
204 | * adapter (from its handler, periodic polling, or whatever). | |
205 | * | |
206 | * NOTE that if we manage the IRQ, we *MUST* know if it's level or | |
207 | * edge triggered in order to hand it to the workqueue correctly. | |
208 | * If triggering the alert seems to wedge the system, you probably | |
209 | * should have said it's level triggered. | |
210 | * | |
211 | * This returns the ara client, which should be saved for later use with | |
212 | * i2c_handle_smbus_alert() and ultimately i2c_unregister_device(); or NULL | |
213 | * to indicate an error. | |
214 | */ | |
215 | struct i2c_client *i2c_setup_smbus_alert(struct i2c_adapter *adapter, | |
216 | struct i2c_smbus_alert_setup *setup) | |
217 | { | |
218 | struct i2c_board_info ara_board_info = { | |
219 | I2C_BOARD_INFO("smbus_alert", 0x0c), | |
220 | .platform_data = setup, | |
221 | }; | |
222 | ||
223 | return i2c_new_device(adapter, &ara_board_info); | |
224 | } | |
225 | EXPORT_SYMBOL_GPL(i2c_setup_smbus_alert); | |
226 | ||
227 | /** | |
228 | * i2c_handle_smbus_alert - Handle an SMBus alert | |
229 | * @ara: the ARA client on the relevant adapter | |
230 | * Context: can't sleep | |
231 | * | |
232 | * Helper function to be called from an I2C bus driver's interrupt | |
233 | * handler. It will schedule the alert work, in turn calling the | |
234 | * corresponding I2C device driver's alert function. | |
235 | * | |
236 | * It is assumed that ara is a valid i2c client previously returned by | |
237 | * i2c_setup_smbus_alert(). | |
238 | */ | |
239 | int i2c_handle_smbus_alert(struct i2c_client *ara) | |
240 | { | |
241 | struct i2c_smbus_alert *alert = i2c_get_clientdata(ara); | |
242 | ||
243 | return schedule_work(&alert->alert); | |
244 | } | |
245 | EXPORT_SYMBOL_GPL(i2c_handle_smbus_alert); | |
246 | ||
247 | static int __init i2c_smbus_init(void) | |
248 | { | |
249 | return i2c_add_driver(&smbalert_driver); | |
250 | } | |
251 | ||
252 | static void __exit i2c_smbus_exit(void) | |
253 | { | |
254 | i2c_del_driver(&smbalert_driver); | |
255 | } | |
256 | ||
257 | module_init(i2c_smbus_init); | |
258 | module_exit(i2c_smbus_exit); | |
259 | ||
260 | MODULE_AUTHOR("Jean Delvare <khali@linux-fr.org>"); | |
261 | MODULE_DESCRIPTION("SMBus protocol extensions support"); | |
262 | MODULE_LICENSE("GPL"); |