/drivers/i2c/i2c-smbus.c

  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");