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., 51 Franklin Street, Fifth Floor, Boston,
  20 * MA 02110-1301 USA.
  21 */
  22
  23#include <linux/kernel.h>
  24#include <linux/module.h>
  25#include <linux/device.h>
  26#include <linux/interrupt.h>
  27#include <linux/workqueue.h>
  28#include <linux/i2c.h>
  29#include <linux/i2c-smbus.h>
  30#include <linux/slab.h>
  31
  32struct i2c_smbus_alert {
  33        unsigned int            alert_edge_triggered:1;
  34        int                     irq;
  35        struct work_struct      alert;
  36        struct i2c_client       *ara;           /* Alert response address */
  37};
  38
  39struct alert_data {
  40        unsigned short          addr;
  41        u8                      flag:1;
  42};
  43
  44/* If this is the alerting device, notify its driver */
  45static int smbus_do_alert(struct device *dev, void *addrp)
  46{
  47        struct i2c_client *client = i2c_verify_client(dev);
  48        struct alert_data *data = addrp;
  49
  50        if (!client || client->addr != data->addr)
  51                return 0;
  52        if (client->flags & I2C_CLIENT_TEN)
  53                return 0;
  54
  55        /*
  56         * Drivers should either disable alerts, or provide at least
  57         * a minimal handler.  Lock so client->driver won't change.
  58         */
  59        device_lock(dev);
  60        if (client->driver) {
  61                if (client->driver->alert)
  62                        client->driver->alert(client, data->flag);
  63                else
  64                        dev_warn(&client->dev, "no driver alert()!\n");
  65        } else
  66                dev_dbg(&client->dev, "alert with no driver\n");
  67        device_unlock(dev);
  68
  69        /* Stop iterating after we find the device */
  70        return -EBUSY;
  71}
  72
  73/*
  74 * The alert IRQ handler needs to hand work off to a task which can issue
  75 * SMBus calls, because those sleeping calls can't be made in IRQ context.
  76 */
  77static void smbus_alert(struct work_struct *work)
  78{
  79        struct i2c_smbus_alert *alert;
  80        struct i2c_client *ara;
  81        unsigned short prev_addr = 0;   /* Not a valid address */
  82
  83        alert = container_of(work, struct i2c_smbus_alert, alert);
  84        ara = alert->ara;
  85
  86        for (;;) {
  87                s32 status;
  88                struct alert_data data;
  89
  90                /*
  91                 * Devices with pending alerts reply in address order, low
  92                 * to high, because of slave transmit arbitration.  After
  93                 * responding, an SMBus device stops asserting SMBALERT#.
  94                 *
  95                 * Note that SMBus 2.0 reserves 10-bit addresess for future
  96                 * use.  We neither handle them, nor try to use PEC here.
  97                 */
  98                status = i2c_smbus_read_byte(ara);
  99                if (status < 0)
 100                        break;
 101
 102                data.flag = status & 1;
 103                data.addr = status >> 1;
 104
 105                if (data.addr == prev_addr) {
 106                        dev_warn(&ara->dev, "Duplicate SMBALERT# from dev "
 107                                "0x%02x, skipping\n", data.addr);
 108                        break;
 109                }
 110                dev_dbg(&ara->dev, "SMBALERT# from dev 0x%02x, flag %d\n",
 111                        data.addr, data.flag);
 112
 113                /* Notify driver for the device which issued the alert */
 114                device_for_each_child(&ara->adapter->dev, &data,
 115                                      smbus_do_alert);
 116                prev_addr = data.addr;
 117        }
 118
 119        /* We handled all alerts; re-enable level-triggered IRQs */
 120        if (!alert->alert_edge_triggered)
 121                enable_irq(alert->irq);
 122}
 123
 124static irqreturn_t smbalert_irq(int irq, void *d)
 125{
 126        struct i2c_smbus_alert *alert = d;
 127
 128        /* Disable level-triggered IRQs until we handle them */
 129        if (!alert->alert_edge_triggered)
 130                disable_irq_nosync(irq);
 131
 132        schedule_work(&alert->alert);
 133        return IRQ_HANDLED;
 134}
 135
 136/* Setup SMBALERT# infrastructure */
 137static int smbalert_probe(struct i2c_client *ara,
 138                          const struct i2c_device_id *id)
 139{
 140        struct i2c_smbus_alert_setup *setup = ara->dev.platform_data;
 141        struct i2c_smbus_alert *alert;
 142        struct i2c_adapter *adapter = ara->adapter;
 143        int res;
 144
 145        alert = devm_kzalloc(&ara->dev, sizeof(struct i2c_smbus_alert),
 146                             GFP_KERNEL);
 147        if (!alert)
 148                return -ENOMEM;
 149
 150        alert->alert_edge_triggered = setup->alert_edge_triggered;
 151        alert->irq = setup->irq;
 152        INIT_WORK(&alert->alert, smbus_alert);
 153        alert->ara = ara;
 154
 155        if (setup->irq > 0) {
 156                res = devm_request_irq(&ara->dev, setup->irq, smbalert_irq,
 157                                       0, "smbus_alert", alert);
 158                if (res)
 159                        return res;
 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 and memory resources are managed so they are 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        return 0;
 176}
 177
 178static const struct i2c_device_id smbalert_ids[] = {
 179        { "smbus_alert", 0 },
 180        { /* LIST END */ }
 181};
 182MODULE_DEVICE_TABLE(i2c, smbalert_ids);
 183
 184static struct i2c_driver smbalert_driver = {
 185        .driver = {
 186                .name   = "smbus_alert",
 187        },
 188        .probe          = smbalert_probe,
 189        .remove         = smbalert_remove,
 190        .id_table       = smbalert_ids,
 191};
 192
 193/**
 194 * i2c_setup_smbus_alert - Setup SMBus alert support
 195 * @adapter: the target adapter
 196 * @setup: setup data for the SMBus alert handler
 197 * Context: can sleep
 198 *
 199 * Setup handling of the SMBus alert protocol on a given I2C bus segment.
 200 *
 201 * Handling can be done either through our IRQ handler, or by the
 202 * adapter (from its handler, periodic polling, or whatever).
 203 *
 204 * NOTE that if we manage the IRQ, we *MUST* know if it's level or
 205 * edge triggered in order to hand it to the workqueue correctly.
 206 * If triggering the alert seems to wedge the system, you probably
 207 * should have said it's level triggered.
 208 *
 209 * This returns the ara client, which should be saved for later use with
 210 * i2c_handle_smbus_alert() and ultimately i2c_unregister_device(); or NULL
 211 * to indicate an error.
 212 */
 213struct i2c_client *i2c_setup_smbus_alert(struct i2c_adapter *adapter,
 214                                         struct i2c_smbus_alert_setup *setup)
 215{
 216        struct i2c_board_info ara_board_info = {
 217                I2C_BOARD_INFO("smbus_alert", 0x0c),
 218                .platform_data = setup,
 219        };
 220
 221        return i2c_new_device(adapter, &ara_board_info);
 222}
 223EXPORT_SYMBOL_GPL(i2c_setup_smbus_alert);
 224
 225/**
 226 * i2c_handle_smbus_alert - Handle an SMBus alert
 227 * @ara: the ARA client on the relevant adapter
 228 * Context: can't sleep
 229 *
 230 * Helper function to be called from an I2C bus driver's interrupt
 231 * handler. It will schedule the alert work, in turn calling the
 232 * corresponding I2C device driver's alert function.
 233 *
 234 * It is assumed that ara is a valid i2c client previously returned by
 235 * i2c_setup_smbus_alert().
 236 */
 237int i2c_handle_smbus_alert(struct i2c_client *ara)
 238{
 239        struct i2c_smbus_alert *alert = i2c_get_clientdata(ara);
 240
 241        return schedule_work(&alert->alert);
 242}
 243EXPORT_SYMBOL_GPL(i2c_handle_smbus_alert);
 244
 245module_i2c_driver(smbalert_driver);
 246
 247MODULE_AUTHOR("Jean Delvare <khali@linux-fr.org>");
 248MODULE_DESCRIPTION("SMBus protocol extensions support");
 249MODULE_LICENSE("GPL");
 250
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