i2c-smbus.c

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/*
 * i2c-smbus.c - SMBus extensions to the I2C protocol
 *
 * Copyright (C) 2008 David Brownell
 * Copyright (C) 2010 Jean Delvare <[email protected]>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
 * MA 02110-1301 USA.
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/device.h>
#include <linux/interrupt.h>
#include <linux/workqueue.h>
#include <linux/i2c.h>
#include <linux/i2c-smbus.h>
#include <linux/slab.h>

struct i2c_smbus_alert {
    unsigned int        alert_edge_triggered:1;
    int         irq;
    struct work_struct  alert;
    struct i2c_client   *ara;       /* Alert response address */
};

struct alert_data {
    unsigned short      addr;
    u8          flag:1;
};

/* 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;

    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 client->driver won't change.
     */
    device_lock(dev);
    if (client->driver) {
        if (client->driver->alert)
            client->driver->alert(client, data->flag);
        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 void smbus_alert(struct work_struct *work)
{
    struct i2c_smbus_alert *alert;
    struct i2c_client *ara;
    unsigned short prev_addr = 0;   /* Not a valid address */

    alert = container_of(work, struct i2c_smbus_alert, alert);
    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 addresess for future
         * use.  We neither handle them, nor try to use PEC here.
         */
        status = i2c_smbus_read_byte(ara);
        if (status < 0)
            break;

        data.flag = status & 1;
        data.addr = status >> 1;

        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.flag);

        /* Notify driver for the device which issued the alert */
        device_for_each_child(&ara->adapter->dev, &data,
                      smbus_do_alert);
        prev_addr = data.addr;
    }

    /* We handled all alerts; re-enable level-triggered IRQs */
    if (!alert->alert_edge_triggered)
        enable_irq(alert->irq);
}

static irqreturn_t smbalert_irq(int irq, void *d)
{
    struct i2c_smbus_alert *alert = d;

    /* Disable level-triggered IRQs until we handle them */
    if (!alert->alert_edge_triggered)
        disable_irq_nosync(irq);

    schedule_work(&alert->alert);
    return IRQ_HANDLED;
}

/* Setup SMBALERT# infrastructure */
static int smbalert_probe(struct i2c_client *ara,
              const struct i2c_device_id *id)
{
    struct i2c_smbus_alert_setup *setup = ara->dev.platform_data;
    struct i2c_smbus_alert *alert;
    struct i2c_adapter *adapter = ara->adapter;
    int res;

    alert = devm_kzalloc(&ara->dev, sizeof(struct i2c_smbus_alert),
                 GFP_KERNEL);
    if (!alert)
        return -ENOMEM;

    alert->alert_edge_triggered = setup->alert_edge_triggered;
    alert->irq = setup->irq;
    INIT_WORK(&alert->alert, smbus_alert);
    alert->ara = ara;

    if (setup->irq > 0) {
        res = devm_request_irq(&ara->dev, setup->irq, smbalert_irq,
                       0, "smbus_alert", alert);
        if (res)
            return res;
    }

    i2c_set_clientdata(ara, alert);
    dev_info(&adapter->dev, "supports SMBALERT#, %s trigger\n",
         setup->alert_edge_triggered ? "edge" : "level");

    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,
};

struct i2c_client *i2c_setup_smbus_alert(struct i2c_adapter *adapter,
                     struct i2c_smbus_alert_setup *setup)
{
    struct i2c_board_info ara_board_info = {
        I2C_BOARD_INFO("smbus_alert", 0x0c),
        .platform_data = setup,
    };

    return i2c_new_device(adapter, &ara_board_info);
}
EXPORT_SYMBOL_GPL(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 <[email protected]>");
MODULE_DESCRIPTION("SMBus protocol extensions support");
MODULE_LICENSE("GPL");