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 70 ara = alert->ara; 71 72 for (;;) { 73 s32 status; 74 struct alert_data data; 75 76 /* 77 * Devices with pending alerts reply in address order, low 78 * to high, because of slave transmit arbitration. After 79 * responding, an SMBus device stops asserting SMBALERT#. 80 * 81 * Note that SMBus 2.0 reserves 10-bit addresses for future 82 * use. We neither handle them, nor try to use PEC here. 83 */ 84 status = i2c_smbus_read_byte(ara); 85 if (status < 0) 86 break; 87 88 data.data = status & 1; 89 data.addr = status >> 1; 90 data.type = I2C_PROTOCOL_SMBUS_ALERT; 91 92 dev_dbg(&ara->dev, "SMBALERT# from dev 0x%02x, flag %d\n", 93 data.addr, data.data); 94 95 /* Notify driver for the device which issued the alert */ 96 device_for_each_child(&ara->adapter->dev, &data, 97 smbus_do_alert); 98 } 99 100 return IRQ_HANDLED; 101 } 102 103 static void smbalert_work(struct work_struct *work) 104 { 105 struct i2c_smbus_alert *alert; 106 107 alert = container_of(work, struct i2c_smbus_alert, alert); 108 109 smbus_alert(0, alert); 110 111 } 112 113 /* Setup SMBALERT# infrastructure */ 114 static int smbalert_probe(struct i2c_client *ara, 115 const struct i2c_device_id *id) 116 { 117 struct i2c_smbus_alert_setup *setup = dev_get_platdata(&ara->dev); 118 struct i2c_smbus_alert *alert; 119 struct i2c_adapter *adapter = ara->adapter; 120 int res, irq; 121 122 alert = devm_kzalloc(&ara->dev, sizeof(struct i2c_smbus_alert), 123 GFP_KERNEL); 124 if (!alert) 125 return -ENOMEM; 126 127 if (setup) { 128 irq = setup->irq; 129 } else { 130 irq = of_irq_get_byname(adapter->dev.of_node, "smbus_alert"); 131 if (irq <= 0) 132 return irq; 133 } 134 135 INIT_WORK(&alert->alert, smbalert_work); 136 alert->ara = ara; 137 138 if (irq > 0) { 139 res = devm_request_threaded_irq(&ara->dev, irq, 140 NULL, smbus_alert, 141 IRQF_SHARED | IRQF_ONESHOT, 142 "smbus_alert", alert); 143 if (res) 144 return res; 145 } 146 147 i2c_set_clientdata(ara, alert); 148 dev_info(&adapter->dev, "supports SMBALERT#\n"); 149 150 return 0; 151 } 152 153 /* IRQ and memory resources are managed so they are freed automatically */ 154 static int smbalert_remove(struct i2c_client *ara) 155 { 156 struct i2c_smbus_alert *alert = i2c_get_clientdata(ara); 157 158 cancel_work_sync(&alert->alert); 159 return 0; 160 } 161 162 static const struct i2c_device_id smbalert_ids[] = { 163 { "smbus_alert", 0 }, 164 { /* LIST END */ } 165 }; 166 MODULE_DEVICE_TABLE(i2c, smbalert_ids); 167 168 static struct i2c_driver smbalert_driver = { 169 .driver = { 170 .name = "smbus_alert", 171 }, 172 .probe = smbalert_probe, 173 .remove = smbalert_remove, 174 .id_table = smbalert_ids, 175 }; 176 177 /** 178 * i2c_handle_smbus_alert - Handle an SMBus alert 179 * @ara: the ARA client on the relevant adapter 180 * Context: can't sleep 181 * 182 * Helper function to be called from an I2C bus driver's interrupt 183 * handler. It will schedule the alert work, in turn calling the 184 * corresponding I2C device driver's alert function. 185 * 186 * It is assumed that ara is a valid i2c client previously returned by 187 * i2c_setup_smbus_alert(). 188 */ 189 int i2c_handle_smbus_alert(struct i2c_client *ara) 190 { 191 struct i2c_smbus_alert *alert = i2c_get_clientdata(ara); 192 193 return schedule_work(&alert->alert); 194 } 195 EXPORT_SYMBOL_GPL(i2c_handle_smbus_alert); 196 197 module_i2c_driver(smbalert_driver); 198 199 MODULE_AUTHOR("Jean Delvare <jdelvare@suse.de>"); 200 MODULE_DESCRIPTION("SMBus protocol extensions support"); 201 MODULE_LICENSE("GPL"); 202