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 #include <linux/slab.h> 30 31 struct i2c_smbus_alert { 32 unsigned int alert_edge_triggered:1; 33 int irq; 34 struct work_struct alert; 35 struct i2c_client *ara; /* Alert response address */ 36 }; 37 38 struct alert_data { 39 unsigned short addr; 40 u8 flag:1; 41 }; 42 43 /* If this is the alerting device, notify its driver */ 44 static int smbus_do_alert(struct device *dev, void *addrp) 45 { 46 struct i2c_client *client = i2c_verify_client(dev); 47 struct alert_data *data = addrp; 48 49 if (!client || client->addr != data->addr) 50 return 0; 51 if (client->flags & I2C_CLIENT_TEN) 52 return 0; 53 54 /* 55 * Drivers should either disable alerts, or provide at least 56 * a minimal handler. Lock so client->driver won't change. 57 */ 58 device_lock(dev); 59 if (client->driver) { 60 if (client->driver->alert) 61 client->driver->alert(client, data->flag); 62 else 63 dev_warn(&client->dev, "no driver alert()!\n"); 64 } else 65 dev_dbg(&client->dev, "alert with no driver\n"); 66 device_unlock(dev); 67 68 /* Stop iterating after we find the device */ 69 return -EBUSY; 70 } 71 72 /* 73 * The alert IRQ handler needs to hand work off to a task which can issue 74 * SMBus calls, because those sleeping calls can't be made in IRQ context. 75 */ 76 static void smbus_alert(struct work_struct *work) 77 { 78 struct i2c_smbus_alert *alert; 79 struct i2c_client *ara; 80 unsigned short prev_addr = 0; /* Not a valid address */ 81 82 alert = container_of(work, struct i2c_smbus_alert, alert); 83 ara = alert->ara; 84 85 for (;;) { 86 s32 status; 87 struct alert_data data; 88 89 /* 90 * Devices with pending alerts reply in address order, low 91 * to high, because of slave transmit arbitration. After 92 * responding, an SMBus device stops asserting SMBALERT#. 93 * 94 * Note that SMBus 2.0 reserves 10-bit addresess for future 95 * use. We neither handle them, nor try to use PEC here. 96 */ 97 status = i2c_smbus_read_byte(ara); 98 if (status < 0) 99 break; 100 101 data.flag = status & 1; 102 data.addr = status >> 1; 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.flag); 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 = ara->dev.platform_data; 140 struct i2c_smbus_alert *alert; 141 struct i2c_adapter *adapter = ara->adapter; 142 int res; 143 144 alert = kzalloc(sizeof(struct i2c_smbus_alert), GFP_KERNEL); 145 if (!alert) 146 return -ENOMEM; 147 148 alert->alert_edge_triggered = setup->alert_edge_triggered; 149 alert->irq = setup->irq; 150 INIT_WORK(&alert->alert, smbus_alert); 151 alert->ara = ara; 152 153 if (setup->irq > 0) { 154 res = devm_request_irq(&ara->dev, setup->irq, smbalert_irq, 155 0, "smbus_alert", alert); 156 if (res) { 157 kfree(alert); 158 return res; 159 } 160 } 161 162 i2c_set_clientdata(ara, alert); 163 dev_info(&adapter->dev, "supports SMBALERT#, %s trigger\n", 164 setup->alert_edge_triggered ? "edge" : "level"); 165 166 return 0; 167 } 168 169 /* IRQ resource is managed so it is 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); 175 176 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"); 263