kernel-ark/drivers/i2c/i2c-smbus.c
Benjamin Tissoires 4d5538f588 i2c: use an IRQ to report Host Notify events, not alert
The current SMBus Host Notify implementation relies on .alert() to
relay its notifications. However, the use cases where SMBus Host
Notify is needed currently is to signal data ready on touchpads.

This is closer to an IRQ than a custom API through .alert().
Given that the 2 touchpad manufacturers (Synaptics and Elan) that
use SMBus Host Notify don't put any data in the SMBus payload, the
concept actually matches one to one.

Benefits are multiple:
- simpler code and API: the client will just have an IRQ, and
  nothing needs to be added in the adapter beside internally
  enabling it.
- no more specific workqueue, the threading is handled by IRQ core
  directly (when required)
- no more races when removing the device (the drivers are already
  required to disable irq on remove)
- simpler handling for drivers: use plain regular IRQs
- no more dependency on i2c-smbus for i2c-i801 (and any other adapter)
- the IRQ domain is created automatically when the adapter exports
  the Host Notify capability
- the IRQ are assign only if ACPI, OF and the caller did not assign
  one already
- the domain is automatically destroyed on remove
- fewer lines of code (minus 20, yeah!)

Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
2016-11-24 16:22:06 +01:00

249 lines
6.8 KiB
C

/*
* i2c-smbus.c - SMBus extensions to the I2C protocol
*
* Copyright (C) 2008 David Brownell
* Copyright (C) 2010 Jean Delvare <jdelvare@suse.de>
*
* 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.
*/
#include <linux/device.h>
#include <linux/i2c.h>
#include <linux/i2c-smbus.h>
#include <linux/interrupt.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/workqueue.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;
enum i2c_alert_protocol type;
unsigned int data;
};
/* 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;
struct i2c_driver *driver;
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 the driver won't change.
*/
device_lock(dev);
if (client->dev.driver) {
driver = to_i2c_driver(client->dev.driver);
if (driver->alert)
driver->alert(client, data->type, data->data);
else
dev_warn(&client->dev, "no driver alert()!\n");
} else
dev_dbg(&client->dev, "alert with no driver\n");
device_unlock(dev);
/* 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 addresses for future
* use. We neither handle them, nor try to use PEC here.
*/
status = i2c_smbus_read_byte(ara);
if (status < 0)
break;
data.data = status & 1;
data.addr = status >> 1;
data.type = I2C_PROTOCOL_SMBUS_ALERT;
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.data);
/* 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 = dev_get_platdata(&ara->dev);
struct i2c_smbus_alert *alert;
struct i2c_adapter *adapter = ara->adapter;
int res;
alert = devm_kzalloc(&ara->dev, 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)
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 and memory resources are managed so they are freed automatically */
static int smbalert_remove(struct i2c_client *ara)
{
struct i2c_smbus_alert *alert = i2c_get_clientdata(ara);
cancel_work_sync(&alert->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);
module_i2c_driver(smbalert_driver);
MODULE_AUTHOR("Jean Delvare <jdelvare@suse.de>");
MODULE_DESCRIPTION("SMBus protocol extensions support");
MODULE_LICENSE("GPL");