drivers/i2c/i2c-smbus.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * i2c-smbus.c - SMBus extensions to the I2C protocol
   4  *
   5  * Copyright (C) 2008 David Brownell
   6  * Copyright (C) 2010 Jean Delvare <jdelvare@suse.de>
   7  */
   8
   9 #include <linux/device.h>
  10 #include <linux/i2c.h>
  11 #include <linux/i2c-smbus.h>
  12 #include <linux/interrupt.h>
  13 #include <linux/kernel.h>
  14 #include <linux/module.h>
  15 #include <linux/of_irq.h>
  16 #include <linux/slab.h>
  17 #include <linux/workqueue.h>
  18
  19 struct i2c_smbus_alert {
  20         struct work_struct      alert;
  21         struct i2c_client       *ara;           /* Alert response address */
  22 };
  23
  24 struct alert_data {
  25         unsigned short          addr;
  26         enum i2c_alert_protocol type;
  27         unsigned int            data;
  28 };
  29
  30 /* If this is the alerting device, notify its driver */
  31 static int smbus_do_alert(struct device *dev, void *addrp)
  32 {
  33         struct i2c_client *client = i2c_verify_client(dev);
  34         struct alert_data *data = addrp;
  35         struct i2c_driver *driver;
  36
  37         if (!client || client->addr != data->addr)
  38                 return 0;
  39         if (client->flags & I2C_CLIENT_TEN)
  40                 return 0;
  41
  42         /*
  43          * Drivers should either disable alerts, or provide at least
  44          * a minimal handler.  Lock so the driver won't change.
  45          */
  46         device_lock(dev);
  47         if (client->dev.driver) {
  48                 driver = to_i2c_driver(client->dev.driver);
  49                 if (driver->alert)
  50                         driver->alert(client, data->type, data->data);
  51                 else
  52                         dev_warn(&client->dev, "no driver alert()!\n");
  53         } else
  54                 dev_dbg(&client->dev, "alert with no driver\n");
  55         device_unlock(dev);
  56
  57         /* Stop iterating after we find the device */
  58         return -EBUSY;
  59 }
  60
  61 /*
  62  * The alert IRQ handler needs to hand work off to a task which can issue
  63  * SMBus calls, because those sleeping calls can't be made in IRQ context.
  64  */
  65 static irqreturn_t smbus_alert(int irq, void *d)
  66 {
  67         struct i2c_smbus_alert *alert = d;
  68         struct i2c_client *ara;
  69
  70         ara = alert->ara;
  71
  72         for (;;) {
  73                 s32 status;
  74                 struct alert_data data;
  75
  76                 /*
  77                  * Devices with pending alerts reply in address order, low
  78                  * to high, because of slave transmit arbitration.  After
  79                  * responding, an SMBus device stops asserting SMBALERT#.
  80                  *
  81                  * Note that SMBus 2.0 reserves 10-bit addresses for future
  82                  * use.  We neither handle them, nor try to use PEC here.
  83                  */
  84                 status = i2c_smbus_read_byte(ara);
  85                 if (status < 0)
  86                         break;
  87
  88                 data.data = status & 1;
  89                 data.addr = status >> 1;
  90                 data.type = I2C_PROTOCOL_SMBUS_ALERT;
  91
  92                 dev_dbg(&ara->dev, "SMBALERT# from dev 0x%02x, flag %d\n",
  93                         data.addr, data.data);
  94
  95                 /* Notify driver for the device which issued the alert */
  96                 device_for_each_child(&ara->adapter->dev, &data,
  97                                       smbus_do_alert);
  98         }
  99
 100         return IRQ_HANDLED;
 101 }
 102
 103 static void smbalert_work(struct work_struct *work)
 104 {
 105         struct i2c_smbus_alert *alert;
 106
 107         alert = container_of(work, struct i2c_smbus_alert, alert);
 108
 109         smbus_alert(0, alert);
 110
 111 }
 112
 113 /* Setup SMBALERT# infrastructure */
 114 static int smbalert_probe(struct i2c_client *ara,
 115                           const struct i2c_device_id *id)
 116 {
 117         struct i2c_smbus_alert_setup *setup = dev_get_platdata(&ara->dev);
 118         struct i2c_smbus_alert *alert;
 119         struct i2c_adapter *adapter = ara->adapter;
 120         int res, irq;
 121
 122         alert = devm_kzalloc(&ara->dev, sizeof(struct i2c_smbus_alert),
 123                              GFP_KERNEL);
 124         if (!alert)
 125                 return -ENOMEM;
 126
 127         if (setup) {
 128                 irq = setup->irq;
 129         } else {
 130                 irq = of_irq_get_byname(adapter->dev.of_node, "smbus_alert");
 131                 if (irq <= 0)
 132                         return irq;
 133         }
 134
 135         INIT_WORK(&alert->alert, smbalert_work);
 136         alert->ara = ara;
 137
 138         if (irq > 0) {
 139                 res = devm_request_threaded_irq(&ara->dev, irq,
 140                                                 NULL, smbus_alert,
 141                                                 IRQF_SHARED | IRQF_ONESHOT,
 142                                                 "smbus_alert", alert);
 143                 if (res)
 144                         return res;
 145         }
 146
 147         i2c_set_clientdata(ara, alert);
 148         dev_info(&adapter->dev, "supports SMBALERT#\n");
 149
 150         return 0;
 151 }
 152
 153 /* IRQ and memory resources are managed so they are freed automatically */
 154 static int smbalert_remove(struct i2c_client *ara)
 155 {
 156         struct i2c_smbus_alert *alert = i2c_get_clientdata(ara);
 157
 158         cancel_work_sync(&alert->alert);
 159         return 0;
 160 }
 161
 162 static const struct i2c_device_id smbalert_ids[] = {
 163         { "smbus_alert", 0 },
 164         { /* LIST END */ }
 165 };
 166 MODULE_DEVICE_TABLE(i2c, smbalert_ids);
 167
 168 static struct i2c_driver smbalert_driver = {
 169         .driver = {
 170                 .name   = "smbus_alert",
 171         },
 172         .probe          = smbalert_probe,
 173         .remove         = smbalert_remove,
 174         .id_table       = smbalert_ids,
 175 };
 176
 177 /**
 178  * i2c_handle_smbus_alert - Handle an SMBus alert
 179  * @ara: the ARA client on the relevant adapter
 180  * Context: can't sleep
 181  *
 182  * Helper function to be called from an I2C bus driver's interrupt
 183  * handler. It will schedule the alert work, in turn calling the
 184  * corresponding I2C device driver's alert function.
 185  *
 186  * It is assumed that ara is a valid i2c client previously returned by
 187  * i2c_setup_smbus_alert().
 188  */
 189 int i2c_handle_smbus_alert(struct i2c_client *ara)
 190 {
 191         struct i2c_smbus_alert *alert = i2c_get_clientdata(ara);
 192
 193         return schedule_work(&alert->alert);
 194 }
 195 EXPORT_SYMBOL_GPL(i2c_handle_smbus_alert);
 196
 197 module_i2c_driver(smbalert_driver);
 198
 199 MODULE_AUTHOR("Jean Delvare <jdelvare@suse.de>");
 200 MODULE_DESCRIPTION("SMBus protocol extensions support");
 201 MODULE_LICENSE("GPL");