250 lines
6.9 KiB
C
250 lines
6.9 KiB
C
/*
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* i2c-smbus.c - SMBus extensions to the I2C protocol
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*
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* Copyright (C) 2008 David Brownell
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* Copyright (C) 2010 Jean Delvare <khali@linux-fr.org>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
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* MA 02110-1301 USA.
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*/
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/device.h>
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#include <linux/interrupt.h>
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#include <linux/workqueue.h>
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#include <linux/i2c.h>
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#include <linux/i2c-smbus.h>
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#include <linux/slab.h>
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struct i2c_smbus_alert {
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unsigned int alert_edge_triggered:1;
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int irq;
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struct work_struct alert;
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struct i2c_client *ara; /* Alert response address */
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};
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struct alert_data {
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unsigned short addr;
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u8 flag:1;
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};
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/* If this is the alerting device, notify its driver */
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static int smbus_do_alert(struct device *dev, void *addrp)
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{
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struct i2c_client *client = i2c_verify_client(dev);
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struct alert_data *data = addrp;
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if (!client || client->addr != data->addr)
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return 0;
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if (client->flags & I2C_CLIENT_TEN)
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return 0;
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/*
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* Drivers should either disable alerts, or provide at least
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* a minimal handler. Lock so client->driver won't change.
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*/
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device_lock(dev);
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if (client->driver) {
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if (client->driver->alert)
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client->driver->alert(client, data->flag);
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else
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dev_warn(&client->dev, "no driver alert()!\n");
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} else
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dev_dbg(&client->dev, "alert with no driver\n");
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device_unlock(dev);
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/* Stop iterating after we find the device */
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return -EBUSY;
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}
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/*
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* The alert IRQ handler needs to hand work off to a task which can issue
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* SMBus calls, because those sleeping calls can't be made in IRQ context.
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*/
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static void smbus_alert(struct work_struct *work)
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{
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struct i2c_smbus_alert *alert;
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struct i2c_client *ara;
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unsigned short prev_addr = 0; /* Not a valid address */
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alert = container_of(work, struct i2c_smbus_alert, alert);
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ara = alert->ara;
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for (;;) {
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s32 status;
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struct alert_data data;
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/*
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* Devices with pending alerts reply in address order, low
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* to high, because of slave transmit arbitration. After
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* responding, an SMBus device stops asserting SMBALERT#.
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*
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* Note that SMBus 2.0 reserves 10-bit addresess for future
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* use. We neither handle them, nor try to use PEC here.
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*/
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status = i2c_smbus_read_byte(ara);
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if (status < 0)
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break;
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data.flag = status & 1;
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data.addr = status >> 1;
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if (data.addr == prev_addr) {
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dev_warn(&ara->dev, "Duplicate SMBALERT# from dev "
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"0x%02x, skipping\n", data.addr);
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break;
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}
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dev_dbg(&ara->dev, "SMBALERT# from dev 0x%02x, flag %d\n",
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data.addr, data.flag);
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/* Notify driver for the device which issued the alert */
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device_for_each_child(&ara->adapter->dev, &data,
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smbus_do_alert);
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prev_addr = data.addr;
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}
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/* We handled all alerts; re-enable level-triggered IRQs */
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if (!alert->alert_edge_triggered)
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enable_irq(alert->irq);
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}
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static irqreturn_t smbalert_irq(int irq, void *d)
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{
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struct i2c_smbus_alert *alert = d;
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/* Disable level-triggered IRQs until we handle them */
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if (!alert->alert_edge_triggered)
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disable_irq_nosync(irq);
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schedule_work(&alert->alert);
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return IRQ_HANDLED;
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}
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/* Setup SMBALERT# infrastructure */
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static int smbalert_probe(struct i2c_client *ara,
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const struct i2c_device_id *id)
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{
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struct i2c_smbus_alert_setup *setup = ara->dev.platform_data;
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struct i2c_smbus_alert *alert;
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struct i2c_adapter *adapter = ara->adapter;
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int res;
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alert = devm_kzalloc(&ara->dev, sizeof(struct i2c_smbus_alert),
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GFP_KERNEL);
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if (!alert)
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return -ENOMEM;
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alert->alert_edge_triggered = setup->alert_edge_triggered;
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alert->irq = setup->irq;
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INIT_WORK(&alert->alert, smbus_alert);
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alert->ara = ara;
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if (setup->irq > 0) {
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res = devm_request_irq(&ara->dev, setup->irq, smbalert_irq,
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0, "smbus_alert", alert);
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if (res)
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return res;
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}
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i2c_set_clientdata(ara, alert);
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dev_info(&adapter->dev, "supports SMBALERT#, %s trigger\n",
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setup->alert_edge_triggered ? "edge" : "level");
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return 0;
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}
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/* IRQ and memory resources are managed so they are freed automatically */
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static int smbalert_remove(struct i2c_client *ara)
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{
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struct i2c_smbus_alert *alert = i2c_get_clientdata(ara);
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cancel_work_sync(&alert->alert);
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return 0;
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}
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static const struct i2c_device_id smbalert_ids[] = {
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{ "smbus_alert", 0 },
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{ /* LIST END */ }
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};
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MODULE_DEVICE_TABLE(i2c, smbalert_ids);
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static struct i2c_driver smbalert_driver = {
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.driver = {
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.name = "smbus_alert",
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},
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.probe = smbalert_probe,
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.remove = smbalert_remove,
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.id_table = smbalert_ids,
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};
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/**
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* i2c_setup_smbus_alert - Setup SMBus alert support
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* @adapter: the target adapter
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* @setup: setup data for the SMBus alert handler
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* Context: can sleep
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*
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* Setup handling of the SMBus alert protocol on a given I2C bus segment.
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*
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* Handling can be done either through our IRQ handler, or by the
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* adapter (from its handler, periodic polling, or whatever).
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*
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* NOTE that if we manage the IRQ, we *MUST* know if it's level or
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* edge triggered in order to hand it to the workqueue correctly.
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* If triggering the alert seems to wedge the system, you probably
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* should have said it's level triggered.
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*
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* This returns the ara client, which should be saved for later use with
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* i2c_handle_smbus_alert() and ultimately i2c_unregister_device(); or NULL
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* to indicate an error.
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*/
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struct i2c_client *i2c_setup_smbus_alert(struct i2c_adapter *adapter,
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struct i2c_smbus_alert_setup *setup)
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{
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struct i2c_board_info ara_board_info = {
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I2C_BOARD_INFO("smbus_alert", 0x0c),
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.platform_data = setup,
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};
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return i2c_new_device(adapter, &ara_board_info);
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}
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EXPORT_SYMBOL_GPL(i2c_setup_smbus_alert);
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/**
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* i2c_handle_smbus_alert - Handle an SMBus alert
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* @ara: the ARA client on the relevant adapter
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* Context: can't sleep
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*
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* Helper function to be called from an I2C bus driver's interrupt
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* handler. It will schedule the alert work, in turn calling the
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* corresponding I2C device driver's alert function.
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*
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* It is assumed that ara is a valid i2c client previously returned by
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* i2c_setup_smbus_alert().
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*/
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int i2c_handle_smbus_alert(struct i2c_client *ara)
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{
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struct i2c_smbus_alert *alert = i2c_get_clientdata(ara);
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return schedule_work(&alert->alert);
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}
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EXPORT_SYMBOL_GPL(i2c_handle_smbus_alert);
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module_i2c_driver(smbalert_driver);
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MODULE_AUTHOR("Jean Delvare <khali@linux-fr.org>");
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MODULE_DESCRIPTION("SMBus protocol extensions support");
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MODULE_LICENSE("GPL");
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