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
  30 struct i2c_smbus_alert {
  31         unsigned int            alert_edge_triggered:1;
  32         int                     irq;
  33         struct work_struct      alert;
  34         struct i2c_client       *ara;           /* Alert response address */
  35 };
  36
  37 struct alert_data {
  38         unsigned short          addr;
  39         u8                      flag:1;
  40 };
  41
  42 /* If this is the alerting device, notify its driver */
  43 static int smbus_do_alert(struct device *dev, void *addrp)
  44 {
  45         struct i2c_client *client = i2c_verify_client(dev);
  46         struct alert_data *data = addrp;
  47
  48         if (!client || client->addr != data->addr)
  49                 return 0;
  50         if (client->flags & I2C_CLIENT_TEN)
  51                 return 0;
  52
  53         /*
  54          * Drivers should either disable alerts, or provide at least
  55          * a minimal handler.  Lock so client->driver won't change.
  56          */
  57         device_lock(dev);
  58         if (client->driver) {
  59                 if (client->driver->alert)
  60                         client->driver->alert(client, data->flag);
  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 addresess 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.flag = status & 1;
 101                 data.addr = status >> 1;
 102
 103                 if (data.addr == prev_addr) {
 104                         dev_warn(&ara->dev, "Duplicate SMBALERT# from dev "
 105                                 "0x%02x, skipping\n", data.addr);
 106                         break;
 107                 }
 108                 dev_dbg(&ara->dev, "SMBALERT# from dev 0x%02x, flag %d\n",
 109                         data.addr, data.flag);
 110
 111                 /* Notify driver for the device which issued the alert */
 112                 device_for_each_child(&ara->adapter->dev, &data,
 113                                       smbus_do_alert);
 114                 prev_addr = data.addr;
 115         }
 116
 117         /* We handled all alerts; re-enable level-triggered IRQs */
 118         if (!alert->alert_edge_triggered)
 119                 enable_irq(alert->irq);
 120 }
 121
 122 static irqreturn_t smbalert_irq(int irq, void *d)
 123 {
 124         struct i2c_smbus_alert *alert = d;
 125
 126         /* Disable level-triggered IRQs until we handle them */
 127         if (!alert->alert_edge_triggered)
 128                 disable_irq_nosync(irq);
 129
 130         schedule_work(&alert->alert);
 131         return IRQ_HANDLED;
 132 }
 133
 134 /* Setup SMBALERT# infrastructure */
 135 static int smbalert_probe(struct i2c_client *ara,
 136                           const struct i2c_device_id *id)
 137 {
 138         struct i2c_smbus_alert_setup *setup = ara->dev.platform_data;
 139         struct i2c_smbus_alert *alert;
 140         struct i2c_adapter *adapter = ara->adapter;
 141         int res;
 142
 143         alert = kzalloc(sizeof(struct i2c_smbus_alert), 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                         kfree(alert);
 157                         return res;
 158                 }
 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 resource is managed so it is 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
 175         i2c_set_clientdata(ara, NULL);
 176         kfree(alert);
 177         return 0;
 178 }
 179
 180 static const struct i2c_device_id smbalert_ids[] = {
 181         { "smbus_alert", 0 },
 182         { /* LIST END */ }
 183 };
 184 MODULE_DEVICE_TABLE(i2c, smbalert_ids);
 185
 186 static struct i2c_driver smbalert_driver = {
 187         .driver = {
 188                 .name   = "smbus_alert",
 189         },
 190         .probe          = smbalert_probe,
 191         .remove         = smbalert_remove,
 192         .id_table       = smbalert_ids,
 193 };
 194
 195 /**
 196  * i2c_setup_smbus_alert - Setup SMBus alert support
 197  * @adapter: the target adapter
 198  * @setup: setup data for the SMBus alert handler
 199  * Context: can sleep
 200  *
 201  * Setup handling of the SMBus alert protocol on a given I2C bus segment.
 202  *
 203  * Handling can be done either through our IRQ handler, or by the
 204  * adapter (from its handler, periodic polling, or whatever).
 205  *
 206  * NOTE that if we manage the IRQ, we *MUST* know if it's level or
 207  * edge triggered in order to hand it to the workqueue correctly.
 208  * If triggering the alert seems to wedge the system, you probably
 209  * should have said it's level triggered.
 210  *
 211  * This returns the ara client, which should be saved for later use with
 212  * i2c_handle_smbus_alert() and ultimately i2c_unregister_device(); or NULL
 213  * to indicate an error.
 214  */
 215 struct i2c_client *i2c_setup_smbus_alert(struct i2c_adapter *adapter,
 216                                          struct i2c_smbus_alert_setup *setup)
 217 {
 218         struct i2c_board_info ara_board_info = {
 219                 I2C_BOARD_INFO("smbus_alert", 0x0c),
 220                 .platform_data = setup,
 221         };
 222
 223         return i2c_new_device(adapter, &ara_board_info);
 224 }
 225 EXPORT_SYMBOL_GPL(i2c_setup_smbus_alert);
 226
 227 /**
 228  * i2c_handle_smbus_alert - Handle an SMBus alert
 229  * @ara: the ARA client on the relevant adapter
 230  * Context: can't sleep
 231  *
 232  * Helper function to be called from an I2C bus driver's interrupt
 233  * handler. It will schedule the alert work, in turn calling the
 234  * corresponding I2C device driver's alert function.
 235  *
 236  * It is assumed that ara is a valid i2c client previously returned by
 237  * i2c_setup_smbus_alert().
 238  */
 239 int i2c_handle_smbus_alert(struct i2c_client *ara)
 240 {
 241         struct i2c_smbus_alert *alert = i2c_get_clientdata(ara);
 242
 243         return schedule_work(&alert->alert);
 244 }
 245 EXPORT_SYMBOL_GPL(i2c_handle_smbus_alert);
 246
 247 static int __init i2c_smbus_init(void)
 248 {
 249         return i2c_add_driver(&smbalert_driver);
 250 }
 251
 252 static void __exit i2c_smbus_exit(void)
 253 {
 254         i2c_del_driver(&smbalert_driver);
 255 }
 256
 257 module_init(i2c_smbus_init);
 258 module_exit(i2c_smbus_exit);
 259
 260 MODULE_AUTHOR("Jean Delvare <khali@linux-fr.org>");
 261 MODULE_DESCRIPTION("SMBus protocol extensions support");
 262 MODULE_LICENSE("GPL");