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., 51 Franklin Street, Fifth Floor, Boston,
  20  * MA 02110-1301 USA.
  21  */
  22
  23 #include <linux/kernel.h>
  24 #include <linux/module.h>
  25 #include <linux/device.h>
  26 #include <linux/interrupt.h>
  27 #include <linux/workqueue.h>
  28 #include <linux/i2c.h>
  29 #include <linux/i2c-smbus.h>
  30 #include <linux/slab.h>
  31
  32 struct i2c_smbus_alert {
  33         unsigned int            alert_edge_triggered:1;
  34         int                     irq;
  35         struct work_struct      alert;
  36         struct i2c_client       *ara;           /* Alert response address */
  37 };
  38
  39 struct alert_data {
  40         unsigned short          addr;
  41         u8                      flag:1;
  42 };
  43
  44 /* If this is the alerting device, notify its driver */
  45 static int smbus_do_alert(struct device *dev, void *addrp)
  46 {
  47         struct i2c_client *client = i2c_verify_client(dev);
  48         struct alert_data *data = addrp;
  49         struct i2c_driver *driver;
  50
  51         if (!client || client->addr != data->addr)
  52                 return 0;
  53         if (client->flags & I2C_CLIENT_TEN)
  54                 return 0;
  55
  56         /*
  57          * Drivers should either disable alerts, or provide at least
  58          * a minimal handler.  Lock so the driver won't change.
  59          */
  60         device_lock(dev);
  61         if (client->dev.driver) {
  62                 driver = to_i2c_driver(client->dev.driver);
  63                 if (driver->alert)
  64                         driver->alert(client, data->flag);
  65                 else
  66                         dev_warn(&client->dev, "no driver alert()!\n");
  67         } else
  68                 dev_dbg(&client->dev, "alert with no driver\n");
  69         device_unlock(dev);
  70
  71         /* Stop iterating after we find the device */
  72         return -EBUSY;
  73 }
  74
  75 /*
  76  * The alert IRQ handler needs to hand work off to a task which can issue
  77  * SMBus calls, because those sleeping calls can't be made in IRQ context.
  78  */
  79 static void smbus_alert(struct work_struct *work)
  80 {
  81         struct i2c_smbus_alert *alert;
  82         struct i2c_client *ara;
  83         unsigned short prev_addr = 0;   /* Not a valid address */
  84
  85         alert = container_of(work, struct i2c_smbus_alert, alert);
  86         ara = alert->ara;
  87
  88         for (;;) {
  89                 s32 status;
  90                 struct alert_data data;
  91
  92                 /*
  93                  * Devices with pending alerts reply in address order, low
  94                  * to high, because of slave transmit arbitration.  After
  95                  * responding, an SMBus device stops asserting SMBALERT#.
  96                  *
  97                  * Note that SMBus 2.0 reserves 10-bit addresess for future
  98                  * use.  We neither handle them, nor try to use PEC here.
  99                  */
 100                 status = i2c_smbus_read_byte(ara);
 101                 if (status < 0)
 102                         break;
 103
 104                 data.flag = status & 1;
 105                 data.addr = status >> 1;
 106
 107                 if (data.addr == prev_addr) {
 108                         dev_warn(&ara->dev, "Duplicate SMBALERT# from dev "
 109                                 "0x%02x, skipping\n", data.addr);
 110                         break;
 111                 }
 112                 dev_dbg(&ara->dev, "SMBALERT# from dev 0x%02x, flag %d\n",
 113                         data.addr, data.flag);
 114
 115                 /* Notify driver for the device which issued the alert */
 116                 device_for_each_child(&ara->adapter->dev, &data,
 117                                       smbus_do_alert);
 118                 prev_addr = data.addr;
 119         }
 120
 121         /* We handled all alerts; re-enable level-triggered IRQs */
 122         if (!alert->alert_edge_triggered)
 123                 enable_irq(alert->irq);
 124 }
 125
 126 static irqreturn_t smbalert_irq(int irq, void *d)
 127 {
 128         struct i2c_smbus_alert *alert = d;
 129
 130         /* Disable level-triggered IRQs until we handle them */
 131         if (!alert->alert_edge_triggered)
 132                 disable_irq_nosync(irq);
 133
 134         schedule_work(&alert->alert);
 135         return IRQ_HANDLED;
 136 }
 137
 138 /* Setup SMBALERT# infrastructure */
 139 static int smbalert_probe(struct i2c_client *ara,
 140                           const struct i2c_device_id *id)
 141 {
 142         struct i2c_smbus_alert_setup *setup = dev_get_platdata(&ara->dev);
 143         struct i2c_smbus_alert *alert;
 144         struct i2c_adapter *adapter = ara->adapter;
 145         int res;
 146
 147         alert = devm_kzalloc(&ara->dev, sizeof(struct i2c_smbus_alert),
 148                              GFP_KERNEL);
 149         if (!alert)
 150                 return -ENOMEM;
 151
 152         alert->alert_edge_triggered = setup->alert_edge_triggered;
 153         alert->irq = setup->irq;
 154         INIT_WORK(&alert->alert, smbus_alert);
 155         alert->ara = ara;
 156
 157         if (setup->irq > 0) {
 158                 res = devm_request_irq(&ara->dev, setup->irq, smbalert_irq,
 159                                        0, "smbus_alert", alert);
 160                 if (res)
 161                         return res;
 162         }
 163
 164         i2c_set_clientdata(ara, alert);
 165         dev_info(&adapter->dev, "supports SMBALERT#, %s trigger\n",
 166                  setup->alert_edge_triggered ? "edge" : "level");
 167
 168         return 0;
 169 }
 170
 171 /* IRQ and memory resources are managed so they are freed automatically */
 172 static int smbalert_remove(struct i2c_client *ara)
 173 {
 174         struct i2c_smbus_alert *alert = i2c_get_clientdata(ara);
 175
 176         cancel_work_sync(&alert->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 module_i2c_driver(smbalert_driver);
 248
 249 MODULE_AUTHOR("Jean Delvare <khali@linux-fr.org>");
 250 MODULE_DESCRIPTION("SMBus protocol extensions support");
 251 MODULE_LICENSE("GPL");