linux/drivers/i2c/i2c-smbus.c
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   1/*
   2 * i2c-smbus.c - SMBus extensions to the I2C protocol
   3 *
   4 * Copyright (C) 2008 David Brownell
   5 * Copyright (C) 2010 Jean Delvare <khali@linux-fr.org>
   6 *
   7 * This program is free software; you can redistribute it and/or modify
   8 * it under the terms of the GNU General Public License as published by
   9 * the Free Software Foundation; either version 2 of the License, or
  10 * (at your option) any later version.
  11 *
  12 * This program is distributed in the hope that it will be useful,
  13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15 * GNU General Public License for more details.
  16 *
  17 * You should have received a copy of the GNU General Public License
  18 * along with this program; if not, write to the Free Software
  19 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  20 */
  21
  22#include <linux/kernel.h>
  23#include <linux/module.h>
  24#include <linux/device.h>
  25#include <linux/interrupt.h>
  26#include <linux/workqueue.h>
  27#include <linux/i2c.h>
  28#include <linux/i2c-smbus.h>
  29#include <linux/slab.h>
  30
  31struct i2c_smbus_alert {
  32        unsigned int            alert_edge_triggered:1;
  33        int                     irq;
  34        struct work_struct      alert;
  35        struct i2c_client       *ara;           /* Alert response address */
  36};
  37
  38struct alert_data {
  39        unsigned short          addr;
  40        u8                      flag:1;
  41};
  42
  43/* If this is the alerting device, notify its driver */
  44static int smbus_do_alert(struct device *dev, void *addrp)
  45{
  46        struct i2c_client *client = i2c_verify_client(dev);
  47        struct alert_data *data = addrp;
  48
  49        if (!client || client->addr != data->addr)
  50                return 0;
  51        if (client->flags & I2C_CLIENT_TEN)
  52                return 0;
  53
  54        /*
  55         * Drivers should either disable alerts, or provide at least
  56         * a minimal handler.  Lock so client->driver won't change.
  57         */
  58        device_lock(dev);
  59        if (client->driver) {
  60                if (client->driver->alert)
  61                        client->driver->alert(client, data->flag);
  62                else
  63                        dev_warn(&client->dev, "no driver alert()!\n");
  64        } else
  65                dev_dbg(&client->dev, "alert with no driver\n");
  66        device_unlock(dev);
  67
  68        /* Stop iterating after we find the device */
  69        return -EBUSY;
  70}
  71
  72/*
  73 * The alert IRQ handler needs to hand work off to a task which can issue
  74 * SMBus calls, because those sleeping calls can't be made in IRQ context.
  75 */
  76static void smbus_alert(struct work_struct *work)
  77{
  78        struct i2c_smbus_alert *alert;
  79        struct i2c_client *ara;
  80        unsigned short prev_addr = 0;   /* Not a valid address */
  81
  82        alert = container_of(work, struct i2c_smbus_alert, alert);
  83        ara = alert->ara;
  84
  85        for (;;) {
  86                s32 status;
  87                struct alert_data data;
  88
  89                /*
  90                 * Devices with pending alerts reply in address order, low
  91                 * to high, because of slave transmit arbitration.  After
  92                 * responding, an SMBus device stops asserting SMBALERT#.
  93                 *
  94                 * Note that SMBus 2.0 reserves 10-bit addresess for future
  95                 * use.  We neither handle them, nor try to use PEC here.
  96                 */
  97                status = i2c_smbus_read_byte(ara);
  98                if (status < 0)
  99                        break;
 100
 101                data.flag = status & 1;
 102                data.addr = status >> 1;
 103
 104                if (data.addr == prev_addr) {
 105                        dev_warn(&ara->dev, "Duplicate SMBALERT# from dev "
 106                                "0x%02x, skipping\n", data.addr);
 107                        break;
 108                }
 109                dev_dbg(&ara->dev, "SMBALERT# from dev 0x%02x, flag %d\n",
 110                        data.addr, data.flag);
 111
 112                /* Notify driver for the device which issued the alert */
 113                device_for_each_child(&ara->adapter->dev, &data,
 114                                      smbus_do_alert);
 115                prev_addr = data.addr;
 116        }
 117
 118        /* We handled all alerts; re-enable level-triggered IRQs */
 119        if (!alert->alert_edge_triggered)
 120                enable_irq(alert->irq);
 121}
 122
 123static irqreturn_t smbalert_irq(int irq, void *d)
 124{
 125        struct i2c_smbus_alert *alert = d;
 126
 127        /* Disable level-triggered IRQs until we handle them */
 128        if (!alert->alert_edge_triggered)
 129                disable_irq_nosync(irq);
 130
 131        schedule_work(&alert->alert);
 132        return IRQ_HANDLED;
 133}
 134
 135/* Setup SMBALERT# infrastructure */
 136static int smbalert_probe(struct i2c_client *ara,
 137                          const struct i2c_device_id *id)
 138{
 139        struct i2c_smbus_alert_setup *setup = ara->dev.platform_data;
 140        struct i2c_smbus_alert *alert;
 141        struct i2c_adapter *adapter = ara->adapter;
 142        int res;
 143
 144        alert = kzalloc(sizeof(struct i2c_smbus_alert), GFP_KERNEL);
 145        if (!alert)
 146                return -ENOMEM;
 147
 148        alert->alert_edge_triggered = setup->alert_edge_triggered;
 149        alert->irq = setup->irq;
 150        INIT_WORK(&alert->alert, smbus_alert);
 151        alert->ara = ara;
 152
 153        if (setup->irq > 0) {
 154                res = devm_request_irq(&ara->dev, setup->irq, smbalert_irq,
 155                                       0, "smbus_alert", alert);
 156                if (res) {
 157                        kfree(alert);
 158                        return res;
 159                }
 160        }
 161
 162        i2c_set_clientdata(ara, alert);
 163        dev_info(&adapter->dev, "supports SMBALERT#, %s trigger\n",
 164                 setup->alert_edge_triggered ? "edge" : "level");
 165
 166        return 0;
 167}
 168
 169/* IRQ resource is managed so it is freed automatically */
 170static int smbalert_remove(struct i2c_client *ara)
 171{
 172        struct i2c_smbus_alert *alert = i2c_get_clientdata(ara);
 173
 174        cancel_work_sync(&alert->alert);
 175
 176        kfree(alert);
 177        return 0;
 178}
 179
 180static const struct i2c_device_id smbalert_ids[] = {
 181        { "smbus_alert", 0 },
 182        { /* LIST END */ }
 183};
 184MODULE_DEVICE_TABLE(i2c, smbalert_ids);
 185
 186static struct i2c_driver smbalert_driver = {
 187        .driver = {
 188                .name   = "smbus_alert",
 189        },
 190        .probe          = smbalert_probe,
 191        .remove         = smbalert_remove,
 192        .id_table       = smbalert_ids,
 193};
 194
 195/**
 196 * i2c_setup_smbus_alert - Setup SMBus alert support
 197 * @adapter: the target adapter
 198 * @setup: setup data for the SMBus alert handler
 199 * Context: can sleep
 200 *
 201 * Setup handling of the SMBus alert protocol on a given I2C bus segment.
 202 *
 203 * Handling can be done either through our IRQ handler, or by the
 204 * adapter (from its handler, periodic polling, or whatever).
 205 *
 206 * NOTE that if we manage the IRQ, we *MUST* know if it's level or
 207 * edge triggered in order to hand it to the workqueue correctly.
 208 * If triggering the alert seems to wedge the system, you probably
 209 * should have said it's level triggered.
 210 *
 211 * This returns the ara client, which should be saved for later use with
 212 * i2c_handle_smbus_alert() and ultimately i2c_unregister_device(); or NULL
 213 * to indicate an error.
 214 */
 215struct i2c_client *i2c_setup_smbus_alert(struct i2c_adapter *adapter,
 216                                         struct i2c_smbus_alert_setup *setup)
 217{
 218        struct i2c_board_info ara_board_info = {
 219                I2C_BOARD_INFO("smbus_alert", 0x0c),
 220                .platform_data = setup,
 221        };
 222
 223        return i2c_new_device(adapter, &ara_board_info);
 224}
 225EXPORT_SYMBOL_GPL(i2c_setup_smbus_alert);
 226
 227/**
 228 * i2c_handle_smbus_alert - Handle an SMBus alert
 229 * @ara: the ARA client on the relevant adapter
 230 * Context: can't sleep
 231 *
 232 * Helper function to be called from an I2C bus driver's interrupt
 233 * handler. It will schedule the alert work, in turn calling the
 234 * corresponding I2C device driver's alert function.
 235 *
 236 * It is assumed that ara is a valid i2c client previously returned by
 237 * i2c_setup_smbus_alert().
 238 */
 239int i2c_handle_smbus_alert(struct i2c_client *ara)
 240{
 241        struct i2c_smbus_alert *alert = i2c_get_clientdata(ara);
 242
 243        return schedule_work(&alert->alert);
 244}
 245EXPORT_SYMBOL_GPL(i2c_handle_smbus_alert);
 246
 247static int __init i2c_smbus_init(void)
 248{
 249        return i2c_add_driver(&smbalert_driver);
 250}
 251
 252static void __exit i2c_smbus_exit(void)
 253{
 254        i2c_del_driver(&smbalert_driver);
 255}
 256
 257module_init(i2c_smbus_init);
 258module_exit(i2c_smbus_exit);
 259
 260MODULE_AUTHOR("Jean Delvare <khali@linux-fr.org>");
 261MODULE_DESCRIPTION("SMBus protocol extensions support");
 262MODULE_LICENSE("GPL");
 263