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// SPDX-License-Identifier: GPL-2.0-or-later
/*
* i2c-smbus.c - SMBus extensions to the I2C protocol
*
* Copyright (C) 2008 David Brownell
* Copyright (C) 2010 Jean Delvare <jdelvare@suse.de>
*/
#include <linux/device.h>
#include <linux/i2c.h>
#include <linux/i2c-smbus.h>
#include <linux/interrupt.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/of_irq.h>
#include <linux/slab.h>
#include <linux/workqueue.h>
struct i2c_smbus_alert {
struct work_struct alert;
struct i2c_client *ara; /* Alert response address */
};
struct alert_data {
unsigned short addr;
enum i2c_alert_protocol type;
unsigned int data;
};
/* If this is the alerting device, notify its driver */
static int smbus_do_alert(struct device *dev, void *addrp)
{
struct i2c_client *client = i2c_verify_client(dev);
struct alert_data *data = addrp;
struct i2c_driver *driver;
if (!client || client->addr != data->addr)
return 0;
if (client->flags & I2C_CLIENT_TEN)
return 0;
/*
* Drivers should either disable alerts, or provide at least
* a minimal handler. Lock so the driver won't change.
*/
device_lock(dev);
if (client->dev.driver) {
driver = to_i2c_driver(client->dev.driver);
if (driver->alert)
driver->alert(client, data->type, data->data);
else
dev_warn(&client->dev, "no driver alert()!\n");
} else
dev_dbg(&client->dev, "alert with no driver\n");
device_unlock(dev);
/* Stop iterating after we find the device */
return -EBUSY;
}
/*
* The alert IRQ handler needs to hand work off to a task which can issue
* SMBus calls, because those sleeping calls can't be made in IRQ context.
*/
static irqreturn_t smbus_alert(int irq, void *d)
{
struct i2c_smbus_alert *alert = d;
struct i2c_client *ara;
unsigned short prev_addr = 0; /* Not a valid address */
ara = alert->ara;
for (;;) {
s32 status;
struct alert_data data;
/*
* Devices with pending alerts reply in address order, low
* to high, because of slave transmit arbitration. After
* responding, an SMBus device stops asserting SMBALERT#.
*
* Note that SMBus 2.0 reserves 10-bit addresses for future
* use. We neither handle them, nor try to use PEC here.
*/
status = i2c_smbus_read_byte(ara);
if (status < 0)
break;
data.data = status & 1;
data.addr = status >> 1;
data.type = I2C_PROTOCOL_SMBUS_ALERT;
if (data.addr == prev_addr) {
dev_warn(&ara->dev, "Duplicate SMBALERT# from dev "
"0x%02x, skipping\n", data.addr);
break;
}
dev_dbg(&ara->dev, "SMBALERT# from dev 0x%02x, flag %d\n",
data.addr, data.data);
/* Notify driver for the device which issued the alert */
device_for_each_child(&ara->adapter->dev, &data,
smbus_do_alert);
prev_addr = data.addr;
}
return IRQ_HANDLED;
}
static void smbalert_work(struct work_struct *work)
{
struct i2c_smbus_alert *alert;
alert = container_of(work, struct i2c_smbus_alert, alert);
smbus_alert(0, alert);
}
/* Setup SMBALERT# infrastructure */
static int smbalert_probe(struct i2c_client *ara,
const struct i2c_device_id *id)
{
struct i2c_smbus_alert_setup *setup = dev_get_platdata(&ara->dev);
struct i2c_smbus_alert *alert;
struct i2c_adapter *adapter = ara->adapter;
int res, irq;
alert = devm_kzalloc(&ara->dev, sizeof(struct i2c_smbus_alert),
GFP_KERNEL);
if (!alert)
return -ENOMEM;
if (setup) {
irq = setup->irq;
} else {
irq = of_irq_get_byname(adapter->dev.of_node, "smbus_alert");
if (irq <= 0)
return irq;
}
INIT_WORK(&alert->alert, smbalert_work);
alert->ara = ara;
if (irq > 0) {
res = devm_request_threaded_irq(&ara->dev, irq,
NULL, smbus_alert,
IRQF_SHARED | IRQF_ONESHOT,
"smbus_alert", alert);
if (res)
return res;
}
i2c_set_clientdata(ara, alert);
dev_info(&adapter->dev, "supports SMBALERT#\n");
return 0;
}
/* IRQ and memory resources are managed so they are freed automatically */
static int smbalert_remove(struct i2c_client *ara)
{
struct i2c_smbus_alert *alert = i2c_get_clientdata(ara);
cancel_work_sync(&alert->alert);
return 0;
}
static const struct i2c_device_id smbalert_ids[] = {
{ "smbus_alert", 0 },
{ /* LIST END */ }
};
MODULE_DEVICE_TABLE(i2c, smbalert_ids);
static struct i2c_driver smbalert_driver = {
.driver = {
.name = "smbus_alert",
},
.probe = smbalert_probe,
.remove = smbalert_remove,
.id_table = smbalert_ids,
};
/**
* i2c_handle_smbus_alert - Handle an SMBus alert
* @ara: the ARA client on the relevant adapter
* Context: can't sleep
*
* Helper function to be called from an I2C bus driver's interrupt
* handler. It will schedule the alert work, in turn calling the
* corresponding I2C device driver's alert function.
*
* It is assumed that ara is a valid i2c client previously returned by
* i2c_setup_smbus_alert().
*/
int i2c_handle_smbus_alert(struct i2c_client *ara)
{
struct i2c_smbus_alert *alert = i2c_get_clientdata(ara);
return schedule_work(&alert->alert);
}
EXPORT_SYMBOL_GPL(i2c_handle_smbus_alert);
module_i2c_driver(smbalert_driver);
MODULE_AUTHOR("Jean Delvare <jdelvare@suse.de>");
MODULE_DESCRIPTION("SMBus protocol extensions support");
MODULE_LICENSE("GPL");
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