// 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");