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/kernel.h>
19#include <linux/module.h>
20#include <linux/device.h>
21#include <linux/interrupt.h>
22#include <linux/workqueue.h>
23#include <linux/i2c.h>
24#include <linux/i2c-smbus.h>
25#include <linux/slab.h>
26
27struct i2c_smbus_alert {
28	unsigned int		alert_edge_triggered:1;
29	int			irq;
30	struct work_struct	alert;
31	struct i2c_client	*ara;		/* Alert response address */
32};
33
34struct alert_data {
35	unsigned short		addr;
36	u8			flag:1;
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->flag);
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 void smbus_alert(struct work_struct *work)
75{
76	struct i2c_smbus_alert *alert;
77	struct i2c_client *ara;
78	unsigned short prev_addr = 0;	/* Not a valid address */
79
80	alert = container_of(work, struct i2c_smbus_alert, alert);
81	ara = alert->ara;
82
83	for (;;) {
84		s32 status;
85		struct alert_data data;
86
87		/*
88		 * Devices with pending alerts reply in address order, low
89		 * to high, because of slave transmit arbitration.  After
90		 * responding, an SMBus device stops asserting SMBALERT#.
91		 *
92		 * Note that SMBus 2.0 reserves 10-bit addresess for future
93		 * use.  We neither handle them, nor try to use PEC here.
94		 */
95		status = i2c_smbus_read_byte(ara);
96		if (status < 0)
97			break;
98
99		data.flag = status & 1;
100		data.addr = status >> 1;
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.flag);
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	/* We handled all alerts; re-enable level-triggered IRQs */
117	if (!alert->alert_edge_triggered)
118		enable_irq(alert->irq);
119}
120
121static irqreturn_t smbalert_irq(int irq, void *d)
122{
123	struct i2c_smbus_alert *alert = d;
124
125	/* Disable level-triggered IRQs until we handle them */
126	if (!alert->alert_edge_triggered)
127		disable_irq_nosync(irq);
128
129	schedule_work(&alert->alert);
130	return IRQ_HANDLED;
131}
132
133/* Setup SMBALERT# infrastructure */
134static int smbalert_probe(struct i2c_client *ara,
135			  const struct i2c_device_id *id)
136{
137	struct i2c_smbus_alert_setup *setup = dev_get_platdata(&ara->dev);
138	struct i2c_smbus_alert *alert;
139	struct i2c_adapter *adapter = ara->adapter;
140	int res;
141
142	alert = devm_kzalloc(&ara->dev, sizeof(struct i2c_smbus_alert),
143			     GFP_KERNEL);
144	if (!alert)
145		return -ENOMEM;
146
147	alert->alert_edge_triggered = setup->alert_edge_triggered;
148	alert->irq = setup->irq;
149	INIT_WORK(&alert->alert, smbus_alert);
150	alert->ara = ara;
151
152	if (setup->irq > 0) {
153		res = devm_request_irq(&ara->dev, setup->irq, smbalert_irq,
154				       0, "smbus_alert", alert);
155		if (res)
156			return res;
157	}
158
159	i2c_set_clientdata(ara, alert);
160	dev_info(&adapter->dev, "supports SMBALERT#, %s trigger\n",
161		 setup->alert_edge_triggered ? "edge" : "level");
162
163	return 0;
164}
165
166/* IRQ and memory resources are managed so they are freed automatically */
167static int smbalert_remove(struct i2c_client *ara)
168{
169	struct i2c_smbus_alert *alert = i2c_get_clientdata(ara);
170
171	cancel_work_sync(&alert->alert);
172	return 0;
173}
174
175static const struct i2c_device_id smbalert_ids[] = {
176	{ "smbus_alert", 0 },
177	{ /* LIST END */ }
178};
179MODULE_DEVICE_TABLE(i2c, smbalert_ids);
180
181static struct i2c_driver smbalert_driver = {
182	.driver = {
183		.name	= "smbus_alert",
184	},
185	.probe		= smbalert_probe,
186	.remove		= smbalert_remove,
187	.id_table	= smbalert_ids,
188};
189
190/**
191 * i2c_setup_smbus_alert - Setup SMBus alert support
192 * @adapter: the target adapter
193 * @setup: setup data for the SMBus alert handler
194 * Context: can sleep
195 *
196 * Setup handling of the SMBus alert protocol on a given I2C bus segment.
197 *
198 * Handling can be done either through our IRQ handler, or by the
199 * adapter (from its handler, periodic polling, or whatever).
200 *
201 * NOTE that if we manage the IRQ, we *MUST* know if it's level or
202 * edge triggered in order to hand it to the workqueue correctly.
203 * If triggering the alert seems to wedge the system, you probably
204 * should have said it's level triggered.
205 *
206 * This returns the ara client, which should be saved for later use with
207 * i2c_handle_smbus_alert() and ultimately i2c_unregister_device(); or NULL
208 * to indicate an error.
209 */
210struct i2c_client *i2c_setup_smbus_alert(struct i2c_adapter *adapter,
211					 struct i2c_smbus_alert_setup *setup)
212{
213	struct i2c_board_info ara_board_info = {
214		I2C_BOARD_INFO("smbus_alert", 0x0c),
215		.platform_data = setup,
216	};
217
218	return i2c_new_device(adapter, &ara_board_info);
219}
220EXPORT_SYMBOL_GPL(i2c_setup_smbus_alert);
221
222/**
223 * i2c_handle_smbus_alert - Handle an SMBus alert
224 * @ara: the ARA client on the relevant adapter
225 * Context: can't sleep
226 *
227 * Helper function to be called from an I2C bus driver's interrupt
228 * handler. It will schedule the alert work, in turn calling the
229 * corresponding I2C device driver's alert function.
230 *
231 * It is assumed that ara is a valid i2c client previously returned by
232 * i2c_setup_smbus_alert().
233 */
234int i2c_handle_smbus_alert(struct i2c_client *ara)
235{
236	struct i2c_smbus_alert *alert = i2c_get_clientdata(ara);
237
238	return schedule_work(&alert->alert);
239}
240EXPORT_SYMBOL_GPL(i2c_handle_smbus_alert);
241
242module_i2c_driver(smbalert_driver);
243
244MODULE_AUTHOR("Jean Delvare <jdelvare@suse.de>");
245MODULE_DESCRIPTION("SMBus protocol extensions support");
246MODULE_LICENSE("GPL");
247