diff --git a/Documentation/i2c/smbus-protocol b/Documentation/i2c/smbus-protocol
index 9df47441f0e73063c39f39fe22acc1fb3a753416..7c19d1a2bea0a4936a20bfaad6972800c8bf4794 100644
--- a/Documentation/i2c/smbus-protocol
+++ b/Documentation/i2c/smbus-protocol
@@ -185,6 +185,22 @@ the protocol. All ARP communications use slave address 0x61 and
require PEC checksums.
+SMBus Alert
+===========
+
+SMBus Alert was introduced in Revision 1.0 of the specification.
+
+The SMBus alert protocol allows several SMBus slave devices to share a
+single interrupt pin on the SMBus master, while still allowing the master
+to know which slave triggered the interrupt.
+
+This is implemented the following way in the Linux kernel:
+* I2C bus drivers which support SMBus alert should call
+ i2c_setup_smbus_alert() to setup SMBus alert support.
+* I2C drivers for devices which can trigger SMBus alerts should implement
+ the optional alert() callback.
+
+
I2C Block Transactions
======================
diff --git a/drivers/i2c/Makefile b/drivers/i2c/Makefile
index ba26e6cbe74e7eb21a9a3231d84f593aed9342cd..7111c93bd3e69e34573eb830921636bf9048960c 100644
--- a/drivers/i2c/Makefile
+++ b/drivers/i2c/Makefile
@@ -3,7 +3,7 @@
#
obj-$(CONFIG_I2C_BOARDINFO) += i2c-boardinfo.o
-obj-$(CONFIG_I2C) += i2c-core.o
+obj-$(CONFIG_I2C) += i2c-core.o i2c-smbus.o
obj-$(CONFIG_I2C_CHARDEV) += i2c-dev.o
obj-y += busses/ chips/ algos/
diff --git a/drivers/i2c/i2c-smbus.c b/drivers/i2c/i2c-smbus.c
new file mode 100644
index 0000000000000000000000000000000000000000..421278221243bb8c73087f42b1b1979d3b5c4b66
--- /dev/null
+++ b/drivers/i2c/i2c-smbus.c
@@ -0,0 +1,263 @@
+/*
+ * i2c-smbus.c - SMBus extensions to the I2C protocol
+ *
+ * Copyright (C) 2008 David Brownell
+ * Copyright (C) 2010 Jean Delvare <khali@linux-fr.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/device.h>
+#include <linux/semaphore.h>
+#include <linux/interrupt.h>
+#include <linux/workqueue.h>
+#include <linux/i2c.h>
+#include <linux/i2c-smbus.h>
+
+struct i2c_smbus_alert {
+ unsigned int alert_edge_triggered:1;
+ int irq;
+ struct work_struct alert;
+ struct i2c_client *ara; /* Alert response address */
+};
+
+struct alert_data {
+ unsigned short addr;
+ u8 flag:1;
+};
+
+/* If this is the alerting device, notify its driver */
+static int smbus_do_alert(struct device *dev, void *addrp)
+{
+ struct i2c_client *client = i2c_verify_client(dev);
+ struct alert_data *data = addrp;
+
+ if (!client || client->addr != data->addr)
+ return 0;
+ if (client->flags & I2C_CLIENT_TEN)
+ return 0;
+
+ /*
+ * Drivers should either disable alerts, or provide at least
+ * a minimal handler. Lock so client->driver won't change.
+ */
+ down(&dev->sem);
+ if (client->driver) {
+ if (client->driver->alert)
+ client->driver->alert(client, data->flag);
+ else
+ dev_warn(&client->dev, "no driver alert()!\n");
+ } else
+ dev_dbg(&client->dev, "alert with no driver\n");
+ up(&dev->sem);
+
+ /* Stop iterating after we find the device */
+ return -EBUSY;
+}
+
+/*
+ * The alert IRQ handler needs to hand work off to a task which can issue
+ * SMBus calls, because those sleeping calls can't be made in IRQ context.
+ */
+static void smbus_alert(struct work_struct *work)
+{
+ struct i2c_smbus_alert *alert;
+ struct i2c_client *ara;
+ unsigned short prev_addr = 0; /* Not a valid address */
+
+ alert = container_of(work, struct i2c_smbus_alert, alert);
+ ara = alert->ara;
+
+ for (;;) {
+ s32 status;
+ struct alert_data data;
+
+ /*
+ * Devices with pending alerts reply in address order, low
+ * to high, because of slave transmit arbitration. After
+ * responding, an SMBus device stops asserting SMBALERT#.
+ *
+ * Note that SMBus 2.0 reserves 10-bit addresess for future
+ * use. We neither handle them, nor try to use PEC here.
+ */
+ status = i2c_smbus_read_byte(ara);
+ if (status < 0)
+ break;
+
+ data.flag = status & 1;
+ data.addr = status >> 1;
+
+ if (data.addr == prev_addr) {
+ dev_warn(&ara->dev, "Duplicate SMBALERT# from dev "
+ "0x%02x, skipping\n", data.addr);
+ break;
+ }
+ dev_dbg(&ara->dev, "SMBALERT# from dev 0x%02x, flag %d\n",
+ data.addr, data.flag);
+
+ /* Notify driver for the device which issued the alert */
+ device_for_each_child(&ara->adapter->dev, &data,
+ smbus_do_alert);
+ prev_addr = data.addr;
+ }
+
+ /* We handled all alerts; re-enable level-triggered IRQs */
+ if (!alert->alert_edge_triggered)
+ enable_irq(alert->irq);
+}
+
+static irqreturn_t smbalert_irq(int irq, void *d)
+{
+ struct i2c_smbus_alert *alert = d;
+
+ /* Disable level-triggered IRQs until we handle them */
+ if (!alert->alert_edge_triggered)
+ disable_irq_nosync(irq);
+
+ schedule_work(&alert->alert);
+ return IRQ_HANDLED;
+}
+
+/* Setup SMBALERT# infrastructure */
+static int smbalert_probe(struct i2c_client *ara,
+ const struct i2c_device_id *id)
+{
+ struct i2c_smbus_alert_setup *setup = ara->dev.platform_data;
+ struct i2c_smbus_alert *alert;
+ struct i2c_adapter *adapter = ara->adapter;
+ int res;
+
+ alert = kzalloc(sizeof(struct i2c_smbus_alert), GFP_KERNEL);
+ if (!alert)
+ return -ENOMEM;
+
+ alert->alert_edge_triggered = setup->alert_edge_triggered;
+ alert->irq = setup->irq;
+ INIT_WORK(&alert->alert, smbus_alert);
+ alert->ara = ara;
+
+ if (setup->irq > 0) {
+ res = devm_request_irq(&ara->dev, setup->irq, smbalert_irq,
+ 0, "smbus_alert", alert);
+ if (res) {
+ kfree(alert);
+ return res;
+ }
+ }
+
+ i2c_set_clientdata(ara, alert);
+ dev_info(&adapter->dev, "supports SMBALERT#, %s trigger\n",
+ setup->alert_edge_triggered ? "edge" : "level");
+
+ return 0;
+}
+
+/* IRQ resource is managed so it is freed automatically */
+static int smbalert_remove(struct i2c_client *ara)
+{
+ struct i2c_smbus_alert *alert = i2c_get_clientdata(ara);
+
+ cancel_work_sync(&alert->alert);
+
+ i2c_set_clientdata(ara, NULL);
+ kfree(alert);
+ return 0;
+}
+
+static const struct i2c_device_id smbalert_ids[] = {
+ { "smbus_alert", 0 },
+ { /* LIST END */ }
+};
+MODULE_DEVICE_TABLE(i2c, smbalert_ids);
+
+static struct i2c_driver smbalert_driver = {
+ .driver = {
+ .name = "smbus_alert",
+ },
+ .probe = smbalert_probe,
+ .remove = smbalert_remove,
+ .id_table = smbalert_ids,
+};
+
+/**
+ * i2c_setup_smbus_alert - Setup SMBus alert support
+ * @adapter: the target adapter
+ * @setup: setup data for the SMBus alert handler
+ * Context: can sleep
+ *
+ * Setup handling of the SMBus alert protocol on a given I2C bus segment.
+ *
+ * Handling can be done either through our IRQ handler, or by the
+ * adapter (from its handler, periodic polling, or whatever).
+ *
+ * NOTE that if we manage the IRQ, we *MUST* know if it's level or
+ * edge triggered in order to hand it to the workqueue correctly.
+ * If triggering the alert seems to wedge the system, you probably
+ * should have said it's level triggered.
+ *
+ * This returns the ara client, which should be saved for later use with
+ * i2c_handle_smbus_alert() and ultimately i2c_unregister_device(); or NULL
+ * to indicate an error.
+ */
+struct i2c_client *i2c_setup_smbus_alert(struct i2c_adapter *adapter,
+ struct i2c_smbus_alert_setup *setup)
+{
+ struct i2c_board_info ara_board_info = {
+ I2C_BOARD_INFO("smbus_alert", 0x0c),
+ .platform_data = setup,
+ };
+
+ return i2c_new_device(adapter, &ara_board_info);
+}
+EXPORT_SYMBOL_GPL(i2c_setup_smbus_alert);
+
+/**
+ * i2c_handle_smbus_alert - Handle an SMBus alert
+ * @ara: the ARA client on the relevant adapter
+ * Context: can't sleep
+ *
+ * Helper function to be called from an I2C bus driver's interrupt
+ * handler. It will schedule the alert work, in turn calling the
+ * corresponding I2C device driver's alert function.
+ *
+ * It is assumed that ara is a valid i2c client previously returned by
+ * i2c_setup_smbus_alert().
+ */
+int i2c_handle_smbus_alert(struct i2c_client *ara)
+{
+ struct i2c_smbus_alert *alert = i2c_get_clientdata(ara);
+
+ return schedule_work(&alert->alert);
+}
+EXPORT_SYMBOL_GPL(i2c_handle_smbus_alert);
+
+static int __init i2c_smbus_init(void)
+{
+ return i2c_add_driver(&smbalert_driver);
+}
+
+static void __exit i2c_smbus_exit(void)
+{
+ i2c_del_driver(&smbalert_driver);
+}
+
+module_init(i2c_smbus_init);
+module_exit(i2c_smbus_exit);
+
+MODULE_AUTHOR("Jean Delvare <khali@linux-fr.org>");
+MODULE_DESCRIPTION("SMBus protocol extensions support");
+MODULE_LICENSE("GPL");
diff --git a/include/linux/i2c-smbus.h b/include/linux/i2c-smbus.h
new file mode 100644
index 0000000000000000000000000000000000000000..63f57a8c8b313561a59af8044593f871de3a9edc
--- /dev/null
+++ b/include/linux/i2c-smbus.h
@@ -0,0 +1,50 @@
+/*
+ * i2c-smbus.h - SMBus extensions to the I2C protocol
+ *
+ * Copyright (C) 2010 Jean Delvare <khali@linux-fr.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#ifndef _LINUX_I2C_SMBUS_H
+#define _LINUX_I2C_SMBUS_H
+
+#include <linux/i2c.h>
+
+
+/**
+ * i2c_smbus_alert_setup - platform data for the smbus_alert i2c client
+ * @alert_edge_triggered: whether the alert interrupt is edge (1) or level (0)
+ * triggered
+ * @irq: IRQ number, if the smbus_alert driver should take care of interrupt
+ * handling
+ *
+ * If irq is not specified, the smbus_alert driver doesn't take care of
+ * interrupt handling. In that case it is up to the I2C bus driver to either
+ * handle the interrupts or to poll for alerts.
+ *
+ * If irq is specified then it it crucial that alert_edge_triggered is
+ * properly set.
+ */
+struct i2c_smbus_alert_setup {
+ unsigned int alert_edge_triggered:1;
+ int irq;
+};
+
+struct i2c_client *i2c_setup_smbus_alert(struct i2c_adapter *adapter,
+ struct i2c_smbus_alert_setup *setup);
+int i2c_handle_smbus_alert(struct i2c_client *ara);
+
+#endif /* _LINUX_I2C_SMBUS_H */
diff --git a/include/linux/i2c.h b/include/linux/i2c.h
index 02fc617782ef7b5f5046cc9b6ac7df88536e24b9..476abd09c92106d2659fc9a406134371ab11b422 100644
--- a/include/linux/i2c.h
+++ b/include/linux/i2c.h
@@ -152,6 +152,13 @@ struct i2c_driver {
int (*suspend)(struct i2c_client *, pm_message_t mesg);
int (*resume)(struct i2c_client *);
+ /* Alert callback, for example for the SMBus alert protocol.
+ * The format and meaning of the data value depends on the protocol.
+ * For the SMBus alert protocol, there is a single bit of data passed
+ * as the alert response's low bit ("event flag").
+ */
+ void (*alert)(struct i2c_client *, unsigned int data);
+
/* a ioctl like command that can be used to perform specific functions
* with the device.
*/