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 <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
  31 struct 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
  38 struct alert_data {
  39         unsigned short          addr;
  40         u8                      flag:1;
  41 };
  42
  43 /* If this is the alerting device, notify its driver */
  44 static 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  */
  76 static 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
 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 = 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 */
 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
 176         i2c_set_clientdata(ara, NULL);
 177         kfree(alert);
 178         return 0;
 179 }
 180
 181 static const struct i2c_device_id smbalert_ids[] = {
 182         { "smbus_alert", 0 },
 183         { /* LIST END */ }
 184 };
 185 MODULE_DEVICE_TABLE(i2c, smbalert_ids);
 186
 187 static struct i2c_driver smbalert_driver = {
 188         .driver = {
 189                 .name   = "smbus_alert",
 190         },
 191         .probe          = smbalert_probe,
 192         .remove         = smbalert_remove,
 193         .id_table       = smbalert_ids,
 194 };
 195
 196 /**
 197  * i2c_setup_smbus_alert - Setup SMBus alert support
 198  * @adapter: the target adapter
 199  * @setup: setup data for the SMBus alert handler
 200  * Context: can sleep
 201  *
 202  * Setup handling of the SMBus alert protocol on a given I2C bus segment.
 203  *
 204  * Handling can be done either through our IRQ handler, or by the
 205  * adapter (from its handler, periodic polling, or whatever).
 206  *
 207  * NOTE that if we manage the IRQ, we *MUST* know if it's level or
 208  * edge triggered in order to hand it to the workqueue correctly.
 209  * If triggering the alert seems to wedge the system, you probably
 210  * should have said it's level triggered.
 211  *
 212  * This returns the ara client, which should be saved for later use with
 213  * i2c_handle_smbus_alert() and ultimately i2c_unregister_device(); or NULL
 214  * to indicate an error.
 215  */
 216 struct i2c_client *i2c_setup_smbus_alert(struct i2c_adapter *adapter,
 217                                          struct i2c_smbus_alert_setup *setup)
 218 {
 219         struct i2c_board_info ara_board_info = {
 220                 I2C_BOARD_INFO("smbus_alert", 0x0c),
 221                 .platform_data = setup,
 222         };
 223
 224         return i2c_new_device(adapter, &ara_board_info);
 225 }
 226 EXPORT_SYMBOL_GPL(i2c_setup_smbus_alert);
 227
 228 /**
 229  * i2c_handle_smbus_alert - Handle an SMBus alert
 230  * @ara: the ARA client on the relevant adapter
 231  * Context: can't sleep
 232  *
 233  * Helper function to be called from an I2C bus driver's interrupt
 234  * handler. It will schedule the alert work, in turn calling the
 235  * corresponding I2C device driver's alert function.
 236  *
 237  * It is assumed that ara is a valid i2c client previously returned by
 238  * i2c_setup_smbus_alert().
 239  */
 240 int i2c_handle_smbus_alert(struct i2c_client *ara)
 241 {
 242         struct i2c_smbus_alert *alert = i2c_get_clientdata(ara);
 243
 244         return schedule_work(&alert->alert);
 245 }
 246 EXPORT_SYMBOL_GPL(i2c_handle_smbus_alert);
 247
 248 static int __init i2c_smbus_init(void)
 249 {
 250         return i2c_add_driver(&smbalert_driver);
 251 }
 252
 253 static void __exit i2c_smbus_exit(void)
 254 {
 255         i2c_del_driver(&smbalert_driver);
 256 }
 257
 258 module_init(i2c_smbus_init);
 259 module_exit(i2c_smbus_exit);
 260
 261 MODULE_AUTHOR("Jean Delvare <khali@linux-fr.org>");
 262 MODULE_DESCRIPTION("SMBus protocol extensions support");
 263 MODULE_LICENSE("GPL");