1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* 3 * i2c-smbus.c - SMBus extensions to the I2C protocol 4 * 5 * Copyright (C) 2008 David Brownell 6 * Copyright (C) 2010 Jean Delvare <jdelvare@suse.de> 7 */ 8 9 #include <linux/device.h> 10 #include <linux/i2c.h> 11 #include <linux/i2c-smbus.h> 12 #include <linux/interrupt.h> 13 #include <linux/kernel.h> 14 #include <linux/module.h> 15 #include <linux/of_irq.h> 16 #include <linux/slab.h> 17 #include <linux/workqueue.h> 18 19 struct i2c_smbus_alert { 20 struct work_struct alert; 21 struct i2c_client *ara; /* Alert response address */ 22 }; 23 24 struct alert_data { 25 unsigned short addr; 26 enum i2c_alert_protocol type; 27 unsigned int data; 28 }; 29 30 /* If this is the alerting device, notify its driver */ 31 static int smbus_do_alert(struct device *dev, void *addrp) 32 { 33 struct i2c_client *client = i2c_verify_client(dev); 34 struct alert_data *data = addrp; 35 struct i2c_driver *driver; 36 37 if (!client || client->addr != data->addr) 38 return 0; 39 if (client->flags & I2C_CLIENT_TEN) 40 return 0; 41 42 /* 43 * Drivers should either disable alerts, or provide at least 44 * a minimal handler. Lock so the driver won't change. 45 */ 46 device_lock(dev); 47 if (client->dev.driver) { 48 driver = to_i2c_driver(client->dev.driver); 49 if (driver->alert) 50 driver->alert(client, data->type, data->data); 51 else 52 dev_warn(&client->dev, "no driver alert()!\n"); 53 } else 54 dev_dbg(&client->dev, "alert with no driver\n"); 55 device_unlock(dev); 56 57 /* Stop iterating after we find the device */ 58 return -EBUSY; 59 } 60 61 /* 62 * The alert IRQ handler needs to hand work off to a task which can issue 63 * SMBus calls, because those sleeping calls can't be made in IRQ context. 64 */ 65 static irqreturn_t smbus_alert(int irq, void *d) 66 { 67 struct i2c_smbus_alert *alert = d; 68 struct i2c_client *ara; 69 unsigned short prev_addr = 0; /* Not a valid address */ 70 71 ara = alert->ara; 72 73 for (;;) { 74 s32 status; 75 struct alert_data data; 76 77 /* 78 * Devices with pending alerts reply in address order, low 79 * to high, because of slave transmit arbitration. After 80 * responding, an SMBus device stops asserting SMBALERT#. 81 * 82 * Note that SMBus 2.0 reserves 10-bit addresses for future 83 * use. We neither handle them, nor try to use PEC here. 84 */ 85 status = i2c_smbus_read_byte(ara); 86 if (status < 0) 87 break; 88 89 data.data = status & 1; 90 data.addr = status >> 1; 91 data.type = I2C_PROTOCOL_SMBUS_ALERT; 92 93 if (data.addr == prev_addr) { 94 dev_warn(&ara->dev, "Duplicate SMBALERT# from dev " 95 "0x%02x, skipping\n", data.addr); 96 break; 97 } 98 dev_dbg(&ara->dev, "SMBALERT# from dev 0x%02x, flag %d\n", 99 data.addr, data.data); 100 101 /* Notify driver for the device which issued the alert */ 102 device_for_each_child(&ara->adapter->dev, &data, 103 smbus_do_alert); 104 prev_addr = data.addr; 105 } 106 107 return IRQ_HANDLED; 108 } 109 110 static void smbalert_work(struct work_struct *work) 111 { 112 struct i2c_smbus_alert *alert; 113 114 alert = container_of(work, struct i2c_smbus_alert, alert); 115 116 smbus_alert(0, alert); 117 118 } 119 120 /* Setup SMBALERT# infrastructure */ 121 static int smbalert_probe(struct i2c_client *ara, 122 const struct i2c_device_id *id) 123 { 124 struct i2c_smbus_alert_setup *setup = dev_get_platdata(&ara->dev); 125 struct i2c_smbus_alert *alert; 126 struct i2c_adapter *adapter = ara->adapter; 127 int res, irq; 128 129 alert = devm_kzalloc(&ara->dev, sizeof(struct i2c_smbus_alert), 130 GFP_KERNEL); 131 if (!alert) 132 return -ENOMEM; 133 134 if (setup) { 135 irq = setup->irq; 136 } else { 137 irq = of_irq_get_byname(adapter->dev.of_node, "smbus_alert"); 138 if (irq <= 0) 139 return irq; 140 } 141 142 INIT_WORK(&alert->alert, smbalert_work); 143 alert->ara = ara; 144 145 if (irq > 0) { 146 res = devm_request_threaded_irq(&ara->dev, irq, 147 NULL, smbus_alert, 148 IRQF_SHARED | IRQF_ONESHOT, 149 "smbus_alert", alert); 150 if (res) 151 return res; 152 } 153 154 i2c_set_clientdata(ara, alert); 155 dev_info(&adapter->dev, "supports SMBALERT#\n"); 156 157 return 0; 158 } 159 160 /* IRQ and memory resources are managed so they are freed automatically */ 161 static int smbalert_remove(struct i2c_client *ara) 162 { 163 struct i2c_smbus_alert *alert = i2c_get_clientdata(ara); 164 165 cancel_work_sync(&alert->alert); 166 return 0; 167 } 168 169 static const struct i2c_device_id smbalert_ids[] = { 170 { "smbus_alert", 0 }, 171 { /* LIST END */ } 172 }; 173 MODULE_DEVICE_TABLE(i2c, smbalert_ids); 174 175 static struct i2c_driver smbalert_driver = { 176 .driver = { 177 .name = "smbus_alert", 178 }, 179 .probe = smbalert_probe, 180 .remove = smbalert_remove, 181 .id_table = smbalert_ids, 182 }; 183 184 /** 185 * i2c_handle_smbus_alert - Handle an SMBus alert 186 * @ara: the ARA client on the relevant adapter 187 * Context: can't sleep 188 * 189 * Helper function to be called from an I2C bus driver's interrupt 190 * handler. It will schedule the alert work, in turn calling the 191 * corresponding I2C device driver's alert function. 192 * 193 * It is assumed that ara is a valid i2c client previously returned by 194 * i2c_setup_smbus_alert(). 195 */ 196 int i2c_handle_smbus_alert(struct i2c_client *ara) 197 { 198 struct i2c_smbus_alert *alert = i2c_get_clientdata(ara); 199 200 return schedule_work(&alert->alert); 201 } 202 EXPORT_SYMBOL_GPL(i2c_handle_smbus_alert); 203 204 module_i2c_driver(smbalert_driver); 205 206 MODULE_AUTHOR("Jean Delvare <jdelvare@suse.de>"); 207 MODULE_DESCRIPTION("SMBus protocol extensions support"); 208 MODULE_LICENSE("GPL"); 209