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/kernel.h>
  19 #include <linux/module.h>
  20 #include <linux/device.h>
  21 #include <linux/interrupt.h>
  22 #include <linux/workqueue.h>
  23 #include <linux/i2c.h>
  24 #include <linux/i2c-smbus.h>
  25 #include <linux/slab.h>
  26
  27 struct i2c_smbus_alert {
  28         unsigned int            alert_edge_triggered:1;
  29         int                     irq;
  30         struct work_struct      alert;
  31         struct i2c_client       *ara;           /* Alert response address */
  32 };
  33
  34 struct alert_data {
  35         unsigned short          addr;
  36         u8                      flag:1;
  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->flag);
  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 void smbus_alert(struct work_struct *work)
  75 {
  76         struct i2c_smbus_alert *alert;
  77         struct i2c_client *ara;
  78         unsigned short prev_addr = 0;   /* Not a valid address */
  79
  80         alert = container_of(work, struct i2c_smbus_alert, alert);
  81         ara = alert->ara;
  82
  83         for (;;) {
  84                 s32 status;
  85                 struct alert_data data;
  86
  87                 /*
  88                  * Devices with pending alerts reply in address order, low
  89                  * to high, because of slave transmit arbitration.  After
  90                  * responding, an SMBus device stops asserting SMBALERT#.
  91                  *
  92                  * Note that SMBus 2.0 reserves 10-bit addresses for future
  93                  * use.  We neither handle them, nor try to use PEC here.
  94                  */
  95                 status = i2c_smbus_read_byte(ara);
  96                 if (status < 0)
  97                         break;
  98
  99                 data.flag = status & 1;
 100                 data.addr = status >> 1;
 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.flag);
 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         /* We handled all alerts; re-enable level-triggered IRQs */
 117         if (!alert->alert_edge_triggered)
 118                 enable_irq(alert->irq);
 119 }
 120
 121 static irqreturn_t smbalert_irq(int irq, void *d)
 122 {
 123         struct i2c_smbus_alert *alert = d;
 124
 125         /* Disable level-triggered IRQs until we handle them */
 126         if (!alert->alert_edge_triggered)
 127                 disable_irq_nosync(irq);
 128
 129         schedule_work(&alert->alert);
 130         return IRQ_HANDLED;
 131 }
 132
 133 /* Setup SMBALERT# infrastructure */
 134 static int smbalert_probe(struct i2c_client *ara,
 135                           const struct i2c_device_id *id)
 136 {
 137         struct i2c_smbus_alert_setup *setup = dev_get_platdata(&ara->dev);
 138         struct i2c_smbus_alert *alert;
 139         struct i2c_adapter *adapter = ara->adapter;
 140         int res;
 141
 142         alert = devm_kzalloc(&ara->dev, sizeof(struct i2c_smbus_alert),
 143                              GFP_KERNEL);
 144         if (!alert)
 145                 return -ENOMEM;
 146
 147         alert->alert_edge_triggered = setup->alert_edge_triggered;
 148         alert->irq = setup->irq;
 149         INIT_WORK(&alert->alert, smbus_alert);
 150         alert->ara = ara;
 151
 152         if (setup->irq > 0) {
 153                 res = devm_request_irq(&ara->dev, setup->irq, smbalert_irq,
 154                                        0, "smbus_alert", alert);
 155                 if (res)
 156                         return res;
 157         }
 158
 159         i2c_set_clientdata(ara, alert);
 160         dev_info(&adapter->dev, "supports SMBALERT#, %s trigger\n",
 161                  setup->alert_edge_triggered ? "edge" : "level");
 162
 163         return 0;
 164 }
 165
 166 /* IRQ and memory resources are managed so they are freed automatically */
 167 static int smbalert_remove(struct i2c_client *ara)
 168 {
 169         struct i2c_smbus_alert *alert = i2c_get_clientdata(ara);
 170
 171         cancel_work_sync(&alert->alert);
 172         return 0;
 173 }
 174
 175 static const struct i2c_device_id smbalert_ids[] = {
 176         { "smbus_alert", 0 },
 177         { /* LIST END */ }
 178 };
 179 MODULE_DEVICE_TABLE(i2c, smbalert_ids);
 180
 181 static struct i2c_driver smbalert_driver = {
 182         .driver = {
 183                 .name   = "smbus_alert",
 184         },
 185         .probe          = smbalert_probe,
 186         .remove         = smbalert_remove,
 187         .id_table       = smbalert_ids,
 188 };
 189
 190 /**
 191  * i2c_setup_smbus_alert - Setup SMBus alert support
 192  * @adapter: the target adapter
 193  * @setup: setup data for the SMBus alert handler
 194  * Context: can sleep
 195  *
 196  * Setup handling of the SMBus alert protocol on a given I2C bus segment.
 197  *
 198  * Handling can be done either through our IRQ handler, or by the
 199  * adapter (from its handler, periodic polling, or whatever).
 200  *
 201  * NOTE that if we manage the IRQ, we *MUST* know if it's level or
 202  * edge triggered in order to hand it to the workqueue correctly.
 203  * If triggering the alert seems to wedge the system, you probably
 204  * should have said it's level triggered.
 205  *
 206  * This returns the ara client, which should be saved for later use with
 207  * i2c_handle_smbus_alert() and ultimately i2c_unregister_device(); or NULL
 208  * to indicate an error.
 209  */
 210 struct i2c_client *i2c_setup_smbus_alert(struct i2c_adapter *adapter,
 211                                          struct i2c_smbus_alert_setup *setup)
 212 {
 213         struct i2c_board_info ara_board_info = {
 214                 I2C_BOARD_INFO("smbus_alert", 0x0c),
 215                 .platform_data = setup,
 216         };
 217
 218         return i2c_new_device(adapter, &ara_board_info);
 219 }
 220 EXPORT_SYMBOL_GPL(i2c_setup_smbus_alert);
 221
 222 /**
 223  * i2c_handle_smbus_alert - Handle an SMBus alert
 224  * @ara: the ARA client on the relevant adapter
 225  * Context: can't sleep
 226  *
 227  * Helper function to be called from an I2C bus driver's interrupt
 228  * handler. It will schedule the alert work, in turn calling the
 229  * corresponding I2C device driver's alert function.
 230  *
 231  * It is assumed that ara is a valid i2c client previously returned by
 232  * i2c_setup_smbus_alert().
 233  */
 234 int i2c_handle_smbus_alert(struct i2c_client *ara)
 235 {
 236         struct i2c_smbus_alert *alert = i2c_get_clientdata(ara);
 237
 238         return schedule_work(&alert->alert);
 239 }
 240 EXPORT_SYMBOL_GPL(i2c_handle_smbus_alert);
 241
 242 module_i2c_driver(smbalert_driver);
 243
 244 MODULE_AUTHOR("Jean Delvare <jdelvare@suse.de>");
 245 MODULE_DESCRIPTION("SMBus protocol extensions support");
 246 MODULE_LICENSE("GPL");