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/slab.h> 25 #include <linux/workqueue.h> 26 27 struct i2c_smbus_alert { 28 unsigned int alert_edge_triggered:1; 29 int irq; 30 struct work_struct alert; 31 struct i2c_client *ara; /* Alert response address */ 32 }; 33 34 struct alert_data { 35 unsigned short addr; 36 enum i2c_alert_protocol type; 37 unsigned int data; 38 }; 39 40 /* If this is the alerting device, notify its driver */ 41 static int smbus_do_alert(struct device *dev, void *addrp) 42 { 43 struct i2c_client *client = i2c_verify_client(dev); 44 struct alert_data *data = addrp; 45 struct i2c_driver *driver; 46 47 if (!client || client->addr != data->addr) 48 return 0; 49 if (client->flags & I2C_CLIENT_TEN) 50 return 0; 51 52 /* 53 * Drivers should either disable alerts, or provide at least 54 * a minimal handler. Lock so the driver won't change. 55 */ 56 device_lock(dev); 57 if (client->dev.driver) { 58 driver = to_i2c_driver(client->dev.driver); 59 if (driver->alert) 60 driver->alert(client, data->type, data->data); 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 addresses 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.data = status & 1; 101 data.addr = status >> 1; 102 data.type = I2C_PROTOCOL_SMBUS_ALERT; 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.data); 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 = dev_get_platdata(&ara->dev); 140 struct i2c_smbus_alert *alert; 141 struct i2c_adapter *adapter = ara->adapter; 142 int res; 143 144 alert = devm_kzalloc(&ara->dev, sizeof(struct i2c_smbus_alert), 145 GFP_KERNEL); 146 if (!alert) 147 return -ENOMEM; 148 149 alert->alert_edge_triggered = setup->alert_edge_triggered; 150 alert->irq = setup->irq; 151 INIT_WORK(&alert->alert, smbus_alert); 152 alert->ara = ara; 153 154 if (setup->irq > 0) { 155 res = devm_request_irq(&ara->dev, setup->irq, smbalert_irq, 156 0, "smbus_alert", alert); 157 if (res) 158 return res; 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 and memory resources are managed so they are 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 return 0; 175 } 176 177 static const struct i2c_device_id smbalert_ids[] = { 178 { "smbus_alert", 0 }, 179 { /* LIST END */ } 180 }; 181 MODULE_DEVICE_TABLE(i2c, smbalert_ids); 182 183 static struct i2c_driver smbalert_driver = { 184 .driver = { 185 .name = "smbus_alert", 186 }, 187 .probe = smbalert_probe, 188 .remove = smbalert_remove, 189 .id_table = smbalert_ids, 190 }; 191 192 /** 193 * i2c_setup_smbus_alert - Setup SMBus alert support 194 * @adapter: the target adapter 195 * @setup: setup data for the SMBus alert handler 196 * Context: can sleep 197 * 198 * Setup handling of the SMBus alert protocol on a given I2C bus segment. 199 * 200 * Handling can be done either through our IRQ handler, or by the 201 * adapter (from its handler, periodic polling, or whatever). 202 * 203 * NOTE that if we manage the IRQ, we *MUST* know if it's level or 204 * edge triggered in order to hand it to the workqueue correctly. 205 * If triggering the alert seems to wedge the system, you probably 206 * should have said it's level triggered. 207 * 208 * This returns the ara client, which should be saved for later use with 209 * i2c_handle_smbus_alert() and ultimately i2c_unregister_device(); or NULL 210 * to indicate an error. 211 */ 212 struct i2c_client *i2c_setup_smbus_alert(struct i2c_adapter *adapter, 213 struct i2c_smbus_alert_setup *setup) 214 { 215 struct i2c_board_info ara_board_info = { 216 I2C_BOARD_INFO("smbus_alert", 0x0c), 217 .platform_data = setup, 218 }; 219 220 return i2c_new_device(adapter, &ara_board_info); 221 } 222 EXPORT_SYMBOL_GPL(i2c_setup_smbus_alert); 223 224 /** 225 * i2c_handle_smbus_alert - Handle an SMBus alert 226 * @ara: the ARA client on the relevant adapter 227 * Context: can't sleep 228 * 229 * Helper function to be called from an I2C bus driver's interrupt 230 * handler. It will schedule the alert work, in turn calling the 231 * corresponding I2C device driver's alert function. 232 * 233 * It is assumed that ara is a valid i2c client previously returned by 234 * i2c_setup_smbus_alert(). 235 */ 236 int i2c_handle_smbus_alert(struct i2c_client *ara) 237 { 238 struct i2c_smbus_alert *alert = i2c_get_clientdata(ara); 239 240 return schedule_work(&alert->alert); 241 } 242 EXPORT_SYMBOL_GPL(i2c_handle_smbus_alert); 243 244 module_i2c_driver(smbalert_driver); 245 246 MODULE_AUTHOR("Jean Delvare <jdelvare@suse.de>"); 247 MODULE_DESCRIPTION("SMBus protocol extensions support"); 248 MODULE_LICENSE("GPL"); 249