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| 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 |
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