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 50 if (!client || client->addr != data->addr) 51 return 0; 52 if (client->flags & I2C_CLIENT_TEN) 53 return 0; 54 55 /* 56 * Drivers should either disable alerts, or provide at least 57 * a minimal handler. Lock so client->driver won't change. 58 */ 59 device_lock(dev); 60 if (client->driver) { 61 if (client->driver->alert) 62 client->driver->alert(client, data->flag); 63 else 64 dev_warn(&client->dev, "no driver alert()!\n"); 65 } else 66 dev_dbg(&client->dev, "alert with no driver\n"); 67 device_unlock(dev); 68 69 /* Stop iterating after we find the device */ 70 return -EBUSY; 71 } 72 73 /* 74 * The alert IRQ handler needs to hand work off to a task which can issue 75 * SMBus calls, because those sleeping calls can't be made in IRQ context. 76 */ 77 static void smbus_alert(struct work_struct *work) 78 { 79 struct i2c_smbus_alert *alert; 80 struct i2c_client *ara; 81 unsigned short prev_addr = 0; /* Not a valid address */ 82 83 alert = container_of(work, struct i2c_smbus_alert, alert); 84 ara = alert->ara; 85 86 for (;;) { 87 s32 status; 88 struct alert_data data; 89 90 /* 91 * Devices with pending alerts reply in address order, low 92 * to high, because of slave transmit arbitration. After 93 * responding, an SMBus device stops asserting SMBALERT#. 94 * 95 * Note that SMBus 2.0 reserves 10-bit addresess for future 96 * use. We neither handle them, nor try to use PEC here. 97 */ 98 status = i2c_smbus_read_byte(ara); 99 if (status < 0) 100 break; 101 102 data.flag = status & 1; 103 data.addr = status >> 1; 104 105 if (data.addr == prev_addr) { 106 dev_warn(&ara->dev, "Duplicate SMBALERT# from dev " 107 "0x%02x, skipping\n", data.addr); 108 break; 109 } 110 dev_dbg(&ara->dev, "SMBALERT# from dev 0x%02x, flag %d\n", 111 data.addr, data.flag); 112 113 /* Notify driver for the device which issued the alert */ 114 device_for_each_child(&ara->adapter->dev, &data, 115 smbus_do_alert); 116 prev_addr = data.addr; 117 } 118 119 /* We handled all alerts; re-enable level-triggered IRQs */ 120 if (!alert->alert_edge_triggered) 121 enable_irq(alert->irq); 122 } 123 124 static irqreturn_t smbalert_irq(int irq, void *d) 125 { 126 struct i2c_smbus_alert *alert = d; 127 128 /* Disable level-triggered IRQs until we handle them */ 129 if (!alert->alert_edge_triggered) 130 disable_irq_nosync(irq); 131 132 schedule_work(&alert->alert); 133 return IRQ_HANDLED; 134 } 135 136 /* Setup SMBALERT# infrastructure */ 137 static int smbalert_probe(struct i2c_client *ara, 138 const struct i2c_device_id *id) 139 { 140 struct i2c_smbus_alert_setup *setup = ara->dev.platform_data; 141 struct i2c_smbus_alert *alert; 142 struct i2c_adapter *adapter = ara->adapter; 143 int res; 144 145 alert = kzalloc(sizeof(struct i2c_smbus_alert), 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 kfree(alert); 159 return res; 160 } 161 } 162 163 i2c_set_clientdata(ara, alert); 164 dev_info(&adapter->dev, "supports SMBALERT#, %s trigger\n", 165 setup->alert_edge_triggered ? "edge" : "level"); 166 167 return 0; 168 } 169 170 /* IRQ resource is managed so it is freed automatically */ 171 static int smbalert_remove(struct i2c_client *ara) 172 { 173 struct i2c_smbus_alert *alert = i2c_get_clientdata(ara); 174 175 cancel_work_sync(&alert->alert); 176 177 kfree(alert); 178 return 0; 179 } 180 181 static const struct i2c_device_id smbalert_ids[] = { 182 { "smbus_alert", 0 }, 183 { /* LIST END */ } 184 }; 185 MODULE_DEVICE_TABLE(i2c, smbalert_ids); 186 187 static struct i2c_driver smbalert_driver = { 188 .driver = { 189 .name = "smbus_alert", 190 }, 191 .probe = smbalert_probe, 192 .remove = smbalert_remove, 193 .id_table = smbalert_ids, 194 }; 195 196 /** 197 * i2c_setup_smbus_alert - Setup SMBus alert support 198 * @adapter: the target adapter 199 * @setup: setup data for the SMBus alert handler 200 * Context: can sleep 201 * 202 * Setup handling of the SMBus alert protocol on a given I2C bus segment. 203 * 204 * Handling can be done either through our IRQ handler, or by the 205 * adapter (from its handler, periodic polling, or whatever). 206 * 207 * NOTE that if we manage the IRQ, we *MUST* know if it's level or 208 * edge triggered in order to hand it to the workqueue correctly. 209 * If triggering the alert seems to wedge the system, you probably 210 * should have said it's level triggered. 211 * 212 * This returns the ara client, which should be saved for later use with 213 * i2c_handle_smbus_alert() and ultimately i2c_unregister_device(); or NULL 214 * to indicate an error. 215 */ 216 struct i2c_client *i2c_setup_smbus_alert(struct i2c_adapter *adapter, 217 struct i2c_smbus_alert_setup *setup) 218 { 219 struct i2c_board_info ara_board_info = { 220 I2C_BOARD_INFO("smbus_alert", 0x0c), 221 .platform_data = setup, 222 }; 223 224 return i2c_new_device(adapter, &ara_board_info); 225 } 226 EXPORT_SYMBOL_GPL(i2c_setup_smbus_alert); 227 228 /** 229 * i2c_handle_smbus_alert - Handle an SMBus alert 230 * @ara: the ARA client on the relevant adapter 231 * Context: can't sleep 232 * 233 * Helper function to be called from an I2C bus driver's interrupt 234 * handler. It will schedule the alert work, in turn calling the 235 * corresponding I2C device driver's alert function. 236 * 237 * It is assumed that ara is a valid i2c client previously returned by 238 * i2c_setup_smbus_alert(). 239 */ 240 int i2c_handle_smbus_alert(struct i2c_client *ara) 241 { 242 struct i2c_smbus_alert *alert = i2c_get_clientdata(ara); 243 244 return schedule_work(&alert->alert); 245 } 246 EXPORT_SYMBOL_GPL(i2c_handle_smbus_alert); 247 248 module_i2c_driver(smbalert_driver); 249 250 MODULE_AUTHOR("Jean Delvare <khali@linux-fr.org>"); 251 MODULE_DESCRIPTION("SMBus protocol extensions support"); 252 MODULE_LICENSE("GPL"); 253