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/slab.h>
  25 #include <linux/workqueue.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         enum i2c_alert_protocol type;
  37         unsigned int            data;
  38 };
  39
  40 /* If this is the alerting device, notify its driver */
  41 static int smbus_do_alert(struct device *dev, void *addrp)
  42 {
  43         struct i2c_client *client = i2c_verify_client(dev);
  44         struct alert_data *data = addrp;
  45         struct i2c_driver *driver;
  46
  47         if (!client || client->addr != data->addr)
  48                 return 0;
  49         if (client->flags & I2C_CLIENT_TEN)
  50                 return 0;
  51
  52         /*
  53          * Drivers should either disable alerts, or provide at least
  54          * a minimal handler.  Lock so the driver won't change.
  55          */
  56         device_lock(dev);
  57         if (client->dev.driver) {
  58                 driver = to_i2c_driver(client->dev.driver);
  59                 if (driver->alert)
  60                         driver->alert(client, data->type, data->data);
  61                 else
  62                         dev_warn(&client->dev, "no driver alert()!\n");
  63         } else
  64                 dev_dbg(&client->dev, "alert with no driver\n");
  65         device_unlock(dev);
  66
  67         /* Stop iterating after we find the device */
  68         return -EBUSY;
  69 }
  70
  71 /*
  72  * The alert IRQ handler needs to hand work off to a task which can issue
  73  * SMBus calls, because those sleeping calls can't be made in IRQ context.
  74  */
  75 static void smbus_alert(struct work_struct *work)
  76 {
  77         struct i2c_smbus_alert *alert;
  78         struct i2c_client *ara;
  79         unsigned short prev_addr = 0;   /* Not a valid address */
  80
  81         alert = container_of(work, struct i2c_smbus_alert, alert);
  82         ara = alert->ara;
  83
  84         for (;;) {
  85                 s32 status;
  86                 struct alert_data data;
  87
  88                 /*
  89                  * Devices with pending alerts reply in address order, low
  90                  * to high, because of slave transmit arbitration.  After
  91                  * responding, an SMBus device stops asserting SMBALERT#.
  92                  *
  93                  * Note that SMBus 2.0 reserves 10-bit addresses for future
  94                  * use.  We neither handle them, nor try to use PEC here.
  95                  */
  96                 status = i2c_smbus_read_byte(ara);
  97                 if (status < 0)
  98                         break;
  99
 100                 data.data = status & 1;
 101                 data.addr = status >> 1;
 102                 data.type = I2C_PROTOCOL_SMBUS_ALERT;
 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.data);
 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
 123 static 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 */
 136 static int smbalert_probe(struct i2c_client *ara,
 137                           const struct i2c_device_id *id)
 138 {
 139         struct i2c_smbus_alert_setup *setup = dev_get_platdata(&ara->dev);
 140         struct i2c_smbus_alert *alert;
 141         struct i2c_adapter *adapter = ara->adapter;
 142         int res;
 143
 144         alert = devm_kzalloc(&ara->dev, sizeof(struct i2c_smbus_alert),
 145                              GFP_KERNEL);
 146         if (!alert)
 147                 return -ENOMEM;
 148
 149         alert->alert_edge_triggered = setup->alert_edge_triggered;
 150         alert->irq = setup->irq;
 151         INIT_WORK(&alert->alert, smbus_alert);
 152         alert->ara = ara;
 153
 154         if (setup->irq > 0) {
 155                 res = devm_request_irq(&ara->dev, setup->irq, smbalert_irq,
 156                                        0, "smbus_alert", alert);
 157                 if (res)
 158                         return res;
 159         }
 160
 161         i2c_set_clientdata(ara, alert);
 162         dev_info(&adapter->dev, "supports SMBALERT#, %s trigger\n",
 163                  setup->alert_edge_triggered ? "edge" : "level");
 164
 165         return 0;
 166 }
 167
 168 /* IRQ and memory resources are managed so they are freed automatically */
 169 static int smbalert_remove(struct i2c_client *ara)
 170 {
 171         struct i2c_smbus_alert *alert = i2c_get_clientdata(ara);
 172
 173         cancel_work_sync(&alert->alert);
 174         return 0;
 175 }
 176
 177 static const struct i2c_device_id smbalert_ids[] = {
 178         { "smbus_alert", 0 },
 179         { /* LIST END */ }
 180 };
 181 MODULE_DEVICE_TABLE(i2c, smbalert_ids);
 182
 183 static struct i2c_driver smbalert_driver = {
 184         .driver = {
 185                 .name   = "smbus_alert",
 186         },
 187         .probe          = smbalert_probe,
 188         .remove         = smbalert_remove,
 189         .id_table       = smbalert_ids,
 190 };
 191
 192 /**
 193  * i2c_setup_smbus_alert - Setup SMBus alert support
 194  * @adapter: the target adapter
 195  * @setup: setup data for the SMBus alert handler
 196  * Context: can sleep
 197  *
 198  * Setup handling of the SMBus alert protocol on a given I2C bus segment.
 199  *
 200  * Handling can be done either through our IRQ handler, or by the
 201  * adapter (from its handler, periodic polling, or whatever).
 202  *
 203  * NOTE that if we manage the IRQ, we *MUST* know if it's level or
 204  * edge triggered in order to hand it to the workqueue correctly.
 205  * If triggering the alert seems to wedge the system, you probably
 206  * should have said it's level triggered.
 207  *
 208  * This returns the ara client, which should be saved for later use with
 209  * i2c_handle_smbus_alert() and ultimately i2c_unregister_device(); or NULL
 210  * to indicate an error.
 211  */
 212 struct i2c_client *i2c_setup_smbus_alert(struct i2c_adapter *adapter,
 213                                          struct i2c_smbus_alert_setup *setup)
 214 {
 215         struct i2c_board_info ara_board_info = {
 216                 I2C_BOARD_INFO("smbus_alert", 0x0c),
 217                 .platform_data = setup,
 218         };
 219
 220         return i2c_new_device(adapter, &ara_board_info);
 221 }
 222 EXPORT_SYMBOL_GPL(i2c_setup_smbus_alert);
 223
 224 /**
 225  * i2c_handle_smbus_alert - Handle an SMBus alert
 226  * @ara: the ARA client on the relevant adapter
 227  * Context: can't sleep
 228  *
 229  * Helper function to be called from an I2C bus driver's interrupt
 230  * handler. It will schedule the alert work, in turn calling the
 231  * corresponding I2C device driver's alert function.
 232  *
 233  * It is assumed that ara is a valid i2c client previously returned by
 234  * i2c_setup_smbus_alert().
 235  */
 236 int i2c_handle_smbus_alert(struct i2c_client *ara)
 237 {
 238         struct i2c_smbus_alert *alert = i2c_get_clientdata(ara);
 239
 240         return schedule_work(&alert->alert);
 241 }
 242 EXPORT_SYMBOL_GPL(i2c_handle_smbus_alert);
 243
 244 module_i2c_driver(smbalert_driver);
 245
 246 MODULE_AUTHOR("Jean Delvare <jdelvare@suse.de>");
 247 MODULE_DESCRIPTION("SMBus protocol extensions support");
 248 MODULE_LICENSE("GPL");