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 struct i2c_driver *driver; 50 51 if (!client || client->addr != data->addr) 52 return 0; 53 if (client->flags & I2C_CLIENT_TEN) 54 return 0; 55 56 /* 57 * Drivers should either disable alerts, or provide at least 58 * a minimal handler. Lock so the driver won't change. 59 */ 60 device_lock(dev); 61 if (client->dev.driver) { 62 driver = to_i2c_driver(client->dev.driver); 63 if (driver->alert) 64 driver->alert(client, data->flag); 65 else 66 dev_warn(&client->dev, "no driver alert()!\n"); 67 } else 68 dev_dbg(&client->dev, "alert with no driver\n"); 69 device_unlock(dev); 70 71 /* Stop iterating after we find the device */ 72 return -EBUSY; 73 } 74 75 /* 76 * The alert IRQ handler needs to hand work off to a task which can issue 77 * SMBus calls, because those sleeping calls can't be made in IRQ context. 78 */ 79 static void smbus_alert(struct work_struct *work) 80 { 81 struct i2c_smbus_alert *alert; 82 struct i2c_client *ara; 83 unsigned short prev_addr = 0; /* Not a valid address */ 84 85 alert = container_of(work, struct i2c_smbus_alert, alert); 86 ara = alert->ara; 87 88 for (;;) { 89 s32 status; 90 struct alert_data data; 91 92 /* 93 * Devices with pending alerts reply in address order, low 94 * to high, because of slave transmit arbitration. After 95 * responding, an SMBus device stops asserting SMBALERT#. 96 * 97 * Note that SMBus 2.0 reserves 10-bit addresess for future 98 * use. We neither handle them, nor try to use PEC here. 99 */ 100 status = i2c_smbus_read_byte(ara); 101 if (status < 0) 102 break; 103 104 data.flag = status & 1; 105 data.addr = status >> 1; 106 107 if (data.addr == prev_addr) { 108 dev_warn(&ara->dev, "Duplicate SMBALERT# from dev " 109 "0x%02x, skipping\n", data.addr); 110 break; 111 } 112 dev_dbg(&ara->dev, "SMBALERT# from dev 0x%02x, flag %d\n", 113 data.addr, data.flag); 114 115 /* Notify driver for the device which issued the alert */ 116 device_for_each_child(&ara->adapter->dev, &data, 117 smbus_do_alert); 118 prev_addr = data.addr; 119 } 120 121 /* We handled all alerts; re-enable level-triggered IRQs */ 122 if (!alert->alert_edge_triggered) 123 enable_irq(alert->irq); 124 } 125 126 static irqreturn_t smbalert_irq(int irq, void *d) 127 { 128 struct i2c_smbus_alert *alert = d; 129 130 /* Disable level-triggered IRQs until we handle them */ 131 if (!alert->alert_edge_triggered) 132 disable_irq_nosync(irq); 133 134 schedule_work(&alert->alert); 135 return IRQ_HANDLED; 136 } 137 138 /* Setup SMBALERT# infrastructure */ 139 static int smbalert_probe(struct i2c_client *ara, 140 const struct i2c_device_id *id) 141 { 142 struct i2c_smbus_alert_setup *setup = dev_get_platdata(&ara->dev); 143 struct i2c_smbus_alert *alert; 144 struct i2c_adapter *adapter = ara->adapter; 145 int res; 146 147 alert = devm_kzalloc(&ara->dev, sizeof(struct i2c_smbus_alert), 148 GFP_KERNEL); 149 if (!alert) 150 return -ENOMEM; 151 152 alert->alert_edge_triggered = setup->alert_edge_triggered; 153 alert->irq = setup->irq; 154 INIT_WORK(&alert->alert, smbus_alert); 155 alert->ara = ara; 156 157 if (setup->irq > 0) { 158 res = devm_request_irq(&ara->dev, setup->irq, smbalert_irq, 159 0, "smbus_alert", alert); 160 if (res) 161 return res; 162 } 163 164 i2c_set_clientdata(ara, alert); 165 dev_info(&adapter->dev, "supports SMBALERT#, %s trigger\n", 166 setup->alert_edge_triggered ? "edge" : "level"); 167 168 return 0; 169 } 170 171 /* IRQ and memory resources are managed so they are freed automatically */ 172 static int smbalert_remove(struct i2c_client *ara) 173 { 174 struct i2c_smbus_alert *alert = i2c_get_clientdata(ara); 175 176 cancel_work_sync(&alert->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 module_i2c_driver(smbalert_driver); 248 249 MODULE_AUTHOR("Jean Delvare <khali@linux-fr.org>"); 250 MODULE_DESCRIPTION("SMBus protocol extensions support"); 251 MODULE_LICENSE("GPL"); 252