drivers/i2c/i2c-smbus.c

   1 /*
   2  * i2c-smbus.c - SMBus extensions to the I2C protocol
   3  *
   4  * Copyright (C) 2008 David Brownell
   5  * Copyright (C) 2010 Jean Delvare <jdelvare@suse.de>
   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
  18 #include <linux/device.h>
  19 #include <linux/i2c.h>
  20 #include <linux/i2c-smbus.h>
  21 #include <linux/interrupt.h>
  22 #include <linux/kernel.h>
  23 #include <linux/module.h>
  24 #include <linux/of_irq.h>
  25 #include <linux/slab.h>
  26 #include <linux/workqueue.h>
  27
  28 struct i2c_smbus_alert {
  29         struct work_struct      alert;
  30         struct i2c_client       *ara;           /* Alert response address */
  31 };
  32
  33 struct alert_data {
  34         unsigned short          addr;
  35         enum i2c_alert_protocol type;
  36         unsigned int            data;
  37 };
  38
  39 /* If this is the alerting device, notify its driver */
  40 static int smbus_do_alert(struct device *dev, void *addrp)
  41 {
  42         struct i2c_client *client = i2c_verify_client(dev);
  43         struct alert_data *data = addrp;
  44         struct i2c_driver *driver;
  45
  46         if (!client || client->addr != data->addr)
  47                 return 0;
  48         if (client->flags & I2C_CLIENT_TEN)
  49                 return 0;
  50
  51         /*
  52          * Drivers should either disable alerts, or provide at least
  53          * a minimal handler.  Lock so the driver won't change.
  54          */
  55         device_lock(dev);
  56         if (client->dev.driver) {
  57                 driver = to_i2c_driver(client->dev.driver);
  58                 if (driver->alert)
  59                         driver->alert(client, data->type, data->data);
  60                 else
  61                         dev_warn(&client->dev, "no driver alert()!\n");
  62         } else
  63                 dev_dbg(&client->dev, "alert with no driver\n");
  64         device_unlock(dev);
  65
  66         /* Stop iterating after we find the device */
  67         return -EBUSY;
  68 }
  69
  70 /*
  71  * The alert IRQ handler needs to hand work off to a task which can issue
  72  * SMBus calls, because those sleeping calls can't be made in IRQ context.
  73  */
  74 static irqreturn_t smbus_alert(int irq, void *d)
  75 {
  76         struct i2c_smbus_alert *alert = d;
  77         struct i2c_client *ara;
  78         unsigned short prev_addr = 0;   /* Not a valid address */
  79
  80         ara = alert->ara;
  81
  82         for (;;) {
  83                 s32 status;
  84                 struct alert_data data;
  85
  86                 /*
  87                  * Devices with pending alerts reply in address order, low
  88                  * to high, because of slave transmit arbitration.  After
  89                  * responding, an SMBus device stops asserting SMBALERT#.
  90                  *
  91                  * Note that SMBus 2.0 reserves 10-bit addresses for future
  92                  * use.  We neither handle them, nor try to use PEC here.
  93                  */
  94                 status = i2c_smbus_read_byte(ara);
  95                 if (status < 0)
  96                         break;
  97
  98                 data.data = status & 1;
  99                 data.addr = status >> 1;
 100                 data.type = I2C_PROTOCOL_SMBUS_ALERT;
 101
 102                 if (data.addr == prev_addr) {
 103                         dev_warn(&ara->dev, "Duplicate SMBALERT# from dev "
 104                                 "0x%02x, skipping\n", data.addr);
 105                         break;
 106                 }
 107                 dev_dbg(&ara->dev, "SMBALERT# from dev 0x%02x, flag %d\n",
 108                         data.addr, data.data);
 109
 110                 /* Notify driver for the device which issued the alert */
 111                 device_for_each_child(&ara->adapter->dev, &data,
 112                                       smbus_do_alert);
 113                 prev_addr = data.addr;
 114         }
 115
 116         return IRQ_HANDLED;
 117 }
 118
 119 static void smbalert_work(struct work_struct *work)
 120 {
 121         struct i2c_smbus_alert *alert;
 122
 123         alert = container_of(work, struct i2c_smbus_alert, alert);
 124
 125         smbus_alert(0, alert);
 126
 127 }
 128
 129 /* Setup SMBALERT# infrastructure */
 130 static int smbalert_probe(struct i2c_client *ara,
 131                           const struct i2c_device_id *id)
 132 {
 133         struct i2c_smbus_alert_setup *setup = dev_get_platdata(&ara->dev);
 134         struct i2c_smbus_alert *alert;
 135         struct i2c_adapter *adapter = ara->adapter;
 136         int res, irq;
 137
 138         alert = devm_kzalloc(&ara->dev, sizeof(struct i2c_smbus_alert),
 139                              GFP_KERNEL);
 140         if (!alert)
 141                 return -ENOMEM;
 142
 143         if (setup) {
 144                 irq = setup->irq;
 145         } else {
 146                 irq = of_irq_get_byname(adapter->dev.of_node, "smbus_alert");
 147                 if (irq <= 0)
 148                         return irq;
 149         }
 150
 151         INIT_WORK(&alert->alert, smbalert_work);
 152         alert->ara = ara;
 153
 154         if (irq > 0) {
 155                 res = devm_request_threaded_irq(&ara->dev, irq,
 156                                                 NULL, smbus_alert,
 157                                                 IRQF_SHARED | IRQF_ONESHOT,
 158                                                 "smbus_alert", alert);
 159                 if (res)
 160                         return res;
 161         }
 162
 163         i2c_set_clientdata(ara, alert);
 164         dev_info(&adapter->dev, "supports SMBALERT#\n");
 165
 166         return 0;
 167 }
 168
 169 /* IRQ and memory resources are managed so they are freed automatically */
 170 static 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
 178 static const struct i2c_device_id smbalert_ids[] = {
 179         { "smbus_alert", 0 },
 180         { /* LIST END */ }
 181 };
 182 MODULE_DEVICE_TABLE(i2c, smbalert_ids);
 183
 184 static 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_handle_smbus_alert - Handle an SMBus alert
 195  * @ara: the ARA client on the relevant adapter
 196  * Context: can't sleep
 197  *
 198  * Helper function to be called from an I2C bus driver's interrupt
 199  * handler. It will schedule the alert work, in turn calling the
 200  * corresponding I2C device driver's alert function.
 201  *
 202  * It is assumed that ara is a valid i2c client previously returned by
 203  * i2c_setup_smbus_alert().
 204  */
 205 int i2c_handle_smbus_alert(struct i2c_client *ara)
 206 {
 207         struct i2c_smbus_alert *alert = i2c_get_clientdata(ara);
 208
 209         return schedule_work(&alert->alert);
 210 }
 211 EXPORT_SYMBOL_GPL(i2c_handle_smbus_alert);
 212
 213 module_i2c_driver(smbalert_driver);
 214
 215 MODULE_AUTHOR("Jean Delvare <jdelvare@suse.de>");
 216 MODULE_DESCRIPTION("SMBus protocol extensions support");
 217 MODULE_LICENSE("GPL");