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/of_irq.h> 25 #include <linux/slab.h> 26 #include <linux/workqueue.h> 27 28 struct i2c_smbus_alert { 29 struct work_struct alert; 30 struct i2c_client *ara; /* Alert response address */ 31 }; 32 33 struct alert_data { 34 unsigned short addr; 35 enum i2c_alert_protocol type; 36 unsigned int data; 37 }; 38 39 /* If this is the alerting device, notify its driver */ 40 static int smbus_do_alert(struct device *dev, void *addrp) 41 { 42 struct i2c_client *client = i2c_verify_client(dev); 43 struct alert_data *data = addrp; 44 struct i2c_driver *driver; 45 46 if (!client || client->addr != data->addr) 47 return 0; 48 if (client->flags & I2C_CLIENT_TEN) 49 return 0; 50 51 /* 52 * Drivers should either disable alerts, or provide at least 53 * a minimal handler. Lock so the driver won't change. 54 */ 55 device_lock(dev); 56 if (client->dev.driver) { 57 driver = to_i2c_driver(client->dev.driver); 58 if (driver->alert) 59 driver->alert(client, data->type, data->data); 60 else 61 dev_warn(&client->dev, "no driver alert()!\n"); 62 } else 63 dev_dbg(&client->dev, "alert with no driver\n"); 64 device_unlock(dev); 65 66 /* Stop iterating after we find the device */ 67 return -EBUSY; 68 } 69 70 /* 71 * The alert IRQ handler needs to hand work off to a task which can issue 72 * SMBus calls, because those sleeping calls can't be made in IRQ context. 73 */ 74 static irqreturn_t smbus_alert(int irq, void *d) 75 { 76 struct i2c_smbus_alert *alert = d; 77 struct i2c_client *ara; 78 unsigned short prev_addr = 0; /* Not a valid address */ 79 80 ara = alert->ara; 81 82 for (;;) { 83 s32 status; 84 struct alert_data data; 85 86 /* 87 * Devices with pending alerts reply in address order, low 88 * to high, because of slave transmit arbitration. After 89 * responding, an SMBus device stops asserting SMBALERT#. 90 * 91 * Note that SMBus 2.0 reserves 10-bit addresses for future 92 * use. We neither handle them, nor try to use PEC here. 93 */ 94 status = i2c_smbus_read_byte(ara); 95 if (status < 0) 96 break; 97 98 data.data = status & 1; 99 data.addr = status >> 1; 100 data.type = I2C_PROTOCOL_SMBUS_ALERT; 101 102 if (data.addr == prev_addr) { 103 dev_warn(&ara->dev, "Duplicate SMBALERT# from dev " 104 "0x%02x, skipping\n", data.addr); 105 break; 106 } 107 dev_dbg(&ara->dev, "SMBALERT# from dev 0x%02x, flag %d\n", 108 data.addr, data.data); 109 110 /* Notify driver for the device which issued the alert */ 111 device_for_each_child(&ara->adapter->dev, &data, 112 smbus_do_alert); 113 prev_addr = data.addr; 114 } 115 116 return IRQ_HANDLED; 117 } 118 119 static void smbalert_work(struct work_struct *work) 120 { 121 struct i2c_smbus_alert *alert; 122 123 alert = container_of(work, struct i2c_smbus_alert, alert); 124 125 smbus_alert(0, alert); 126 127 } 128 129 /* Setup SMBALERT# infrastructure */ 130 static int smbalert_probe(struct i2c_client *ara, 131 const struct i2c_device_id *id) 132 { 133 struct i2c_smbus_alert_setup *setup = dev_get_platdata(&ara->dev); 134 struct i2c_smbus_alert *alert; 135 struct i2c_adapter *adapter = ara->adapter; 136 int res, irq; 137 138 alert = devm_kzalloc(&ara->dev, sizeof(struct i2c_smbus_alert), 139 GFP_KERNEL); 140 if (!alert) 141 return -ENOMEM; 142 143 if (setup) { 144 irq = setup->irq; 145 } else { 146 irq = of_irq_get_byname(adapter->dev.of_node, "smbus_alert"); 147 if (irq <= 0) 148 return irq; 149 } 150 151 INIT_WORK(&alert->alert, smbalert_work); 152 alert->ara = ara; 153 154 if (irq > 0) { 155 res = devm_request_threaded_irq(&ara->dev, irq, 156 NULL, smbus_alert, 157 IRQF_SHARED | IRQF_ONESHOT, 158 "smbus_alert", alert); 159 if (res) 160 return res; 161 } 162 163 i2c_set_clientdata(ara, alert); 164 dev_info(&adapter->dev, "supports SMBALERT#\n"); 165 166 return 0; 167 } 168 169 /* IRQ and memory resources are managed so they are 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 return 0; 176 } 177 178 static const struct i2c_device_id smbalert_ids[] = { 179 { "smbus_alert", 0 }, 180 { /* LIST END */ } 181 }; 182 MODULE_DEVICE_TABLE(i2c, smbalert_ids); 183 184 static struct i2c_driver smbalert_driver = { 185 .driver = { 186 .name = "smbus_alert", 187 }, 188 .probe = smbalert_probe, 189 .remove = smbalert_remove, 190 .id_table = smbalert_ids, 191 }; 192 193 /** 194 * i2c_handle_smbus_alert - Handle an SMBus alert 195 * @ara: the ARA client on the relevant adapter 196 * Context: can't sleep 197 * 198 * Helper function to be called from an I2C bus driver's interrupt 199 * handler. It will schedule the alert work, in turn calling the 200 * corresponding I2C device driver's alert function. 201 * 202 * It is assumed that ara is a valid i2c client previously returned by 203 * i2c_setup_smbus_alert(). 204 */ 205 int i2c_handle_smbus_alert(struct i2c_client *ara) 206 { 207 struct i2c_smbus_alert *alert = i2c_get_clientdata(ara); 208 209 return schedule_work(&alert->alert); 210 } 211 EXPORT_SYMBOL_GPL(i2c_handle_smbus_alert); 212 213 module_i2c_driver(smbalert_driver); 214 215 MODULE_AUTHOR("Jean Delvare <jdelvare@suse.de>"); 216 MODULE_DESCRIPTION("SMBus protocol extensions support"); 217 MODULE_LICENSE("GPL"); 218