[PATCH 08/10] Input: add a PS/2 to SMBus platform module

[Benjamin Tissoires]

This driver is a glue between PS/2 devices that enumerate
the RMI4 devices and Elan touchpads to the RMI4 (or Elan)
SMBus driver.

We use an intermediate platform device to not add a
dependency between psmouse and I2C. It also handles
the subtleties of going around the serio mutex lock by
deferring the i2c creation/destruction in a separate
thread.

Signed-off-by: Benjamin Tissoires <benjamin.tissoires@xxxxxxxxxx>
---
 drivers/input/misc/Kconfig     |  11 ++
 drivers/input/misc/Makefile    |   1 +
 drivers/input/misc/ps2_smbus.c | 255 +++++++++++++++++++++++++++++++++++++++++
 drivers/input/rmi4/Kconfig     |   1 +
 4 files changed, 268 insertions(+)
 create mode 100644 drivers/input/misc/ps2_smbus.c

diff --git a/drivers/input/misc/Kconfig b/drivers/input/misc/Kconfig
index 1ae4d96..e0dfefc 100644
--- a/drivers/input/misc/Kconfig
+++ b/drivers/input/misc/Kconfig
@@ -832,4 +832,15 @@ config INPUT_HISI_POWERKEY
 	  To compile this driver as a module, choose M here: the
 	  module will be called hisi_powerkey.
 
+config PS2_SMBUS
+	tristate "Platform Support for PS/2 Nodes also connected over SMBus"
+	depends on I2C
+	help
+	  Say Y here if you want to support RMI4 or Elan devices connected to
+	  an SMB bus but enumerated through PS/2.
+
+	  if unsure, say N.
+	  To compile this driver as a module, choose M here: the module will be
+	  called ps2_smbus.
+
 endif
diff --git a/drivers/input/misc/Makefile b/drivers/input/misc/Makefile
index 0b6d025..094a911 100644
--- a/drivers/input/misc/Makefile
+++ b/drivers/input/misc/Makefile
@@ -57,6 +57,7 @@ obj-$(CONFIG_INPUT_PCSPKR)		+= pcspkr.o
 obj-$(CONFIG_INPUT_PM8941_PWRKEY)	+= pm8941-pwrkey.o
 obj-$(CONFIG_INPUT_PM8XXX_VIBRATOR)	+= pm8xxx-vibrator.o
 obj-$(CONFIG_INPUT_PMIC8XXX_PWRKEY)	+= pmic8xxx-pwrkey.o
+obj-$(CONFIG_PS2_SMBUS)			+= ps2_smbus.o
 obj-$(CONFIG_INPUT_POWERMATE)		+= powermate.o
 obj-$(CONFIG_INPUT_PWM_BEEPER)		+= pwm-beeper.o
 obj-$(CONFIG_INPUT_RB532_BUTTON)	+= rb532_button.o
diff --git a/drivers/input/misc/ps2_smbus.c b/drivers/input/misc/ps2_smbus.c
new file mode 100644
index 0000000..d1f27ed
--- /dev/null
+++ b/drivers/input/misc/ps2_smbus.c
@@ -0,0 +1,255 @@
+/*
+ * Copyright (c) 2017 Red Hat, Inc
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 as published by
+ * the Free Software Foundation.
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/i2c.h>
+#include <linux/platform_device.h>
+#include <linux/rmi.h>
+#include <linux/serio.h>
+#include <linux/slab.h>
+
+MODULE_AUTHOR("Benjamin Tissoires <benjamin.tissoires@xxxxxxxxxx>");
+MODULE_DESCRIPTION("Platform PS/2 - SMBus bridge driver");
+MODULE_LICENSE("GPL");
+
+static struct workqueue_struct *kps2smbus_wq;
+DEFINE_MUTEX(ps2smbus_mutex);
+
+enum ps2smbus_type {
+	PS2SMBUS_SYNAPTICS_RMI4,
+};
+
+struct ps2smbus {
+	struct i2c_client *smbus_client;
+	struct notifier_block i2c_notifier;
+	enum ps2smbus_type type;
+	void *pdata;
+};
+
+enum ps2smbus_event_type {
+	PS2SMBUS_REGISTER_DEVICE,
+	PS2SMBUS_UNREGISTER_DEVICE,
+};
+
+struct ps2smbus_work {
+	struct work_struct work;
+	enum ps2smbus_event_type type;
+	struct ps2smbus *ps2smbus;
+	struct i2c_adapter *adap;
+};
+
+static void ps2smbus_create_rmi4(struct ps2smbus *ps2smbus,
+				 struct i2c_adapter *adap)
+{
+	const struct i2c_board_info i2c_info = {
+		I2C_BOARD_INFO("rmi4_smbus", 0x2c),
+		.platform_data = ps2smbus->pdata,
+		.flags = I2C_CLIENT_HOST_NOTIFY,
+	};
+
+	ps2smbus->smbus_client = i2c_new_device(adap, &i2c_info);
+}
+
+static void ps2smbus_worker(struct work_struct *work)
+{
+	struct ps2smbus_work *ps2smbus_work;
+	struct i2c_client *client;
+
+	ps2smbus_work = container_of(work, struct ps2smbus_work, work);
+	client = ps2smbus_work->ps2smbus->smbus_client;
+
+	mutex_lock(&ps2smbus_mutex);
+
+	switch (ps2smbus_work->type) {
+	case PS2SMBUS_REGISTER_DEVICE:
+		if (ps2smbus_work->ps2smbus->type == PS2SMBUS_SYNAPTICS_RMI4)
+			ps2smbus_create_rmi4(ps2smbus_work->ps2smbus,
+					     ps2smbus_work->adap);
+		break;
+	case PS2SMBUS_UNREGISTER_DEVICE:
+		if (client)
+			i2c_unregister_device(client);
+		break;
+	}
+
+	kfree(ps2smbus_work);
+
+	mutex_unlock(&ps2smbus_mutex);
+}
+
+static int ps2smbus_schedule_work(enum ps2smbus_event_type type,
+				  struct ps2smbus *ps2smbus,
+				  struct i2c_adapter *adap)
+{
+	struct ps2smbus_work *ps2smbus_work;
+
+	ps2smbus_work = kzalloc(sizeof(*ps2smbus_work), GFP_KERNEL);
+	if (!ps2smbus_work)
+		return -ENOMEM;
+
+	ps2smbus_work->type = type;
+	ps2smbus_work->ps2smbus = ps2smbus;
+	ps2smbus_work->adap = adap;
+
+	INIT_WORK(&ps2smbus_work->work, ps2smbus_worker);
+
+	queue_work(kps2smbus_wq, &ps2smbus_work->work);
+
+	return 0;
+}
+
+static int ps2smbus_attach_i2c_device(struct device *dev, void *data)
+{
+	struct ps2smbus *ps2smbus = data;
+	struct i2c_adapter *adap;
+
+	if (dev->type != &i2c_adapter_type)
+		return 0;
+
+	adap = to_i2c_adapter(dev);
+
+	if (!i2c_check_functionality(adap, I2C_FUNC_SMBUS_HOST_NOTIFY))
+		return 0;
+
+	if (ps2smbus->smbus_client)
+		return 0;
+
+	ps2smbus_schedule_work(PS2SMBUS_REGISTER_DEVICE, ps2smbus, adap);
+
+	pr_debug("ps2smbus: adapter [%s] registered\n", adap->name);
+	return 0;
+}
+
+static int ps2smbus_detach_i2c_device(struct device *dev,
+				      struct ps2smbus *ps2smbus)
+{
+	struct i2c_client *client;
+
+	if (dev->type == &i2c_adapter_type)
+		return 0;
+
+	mutex_lock(&ps2smbus_mutex);
+
+	client = to_i2c_client(dev);
+	if (client == ps2smbus->smbus_client)
+		ps2smbus->smbus_client = NULL;
+
+	mutex_unlock(&ps2smbus_mutex);
+
+	pr_debug("ps2smbus: client [%s] unregistered\n", client->name);
+	return 0;
+}
+
+static int ps2smbus_notifier_call(struct notifier_block *nb,
+				  unsigned long action, void *data)
+{
+	struct device *dev = data;
+	struct ps2smbus *ps2smbus;
+
+	ps2smbus = container_of(nb, struct ps2smbus, i2c_notifier);
+
+	switch (action) {
+	case BUS_NOTIFY_ADD_DEVICE:
+		return ps2smbus_attach_i2c_device(dev, ps2smbus);
+	case BUS_NOTIFY_DEL_DEVICE:
+		return ps2smbus_detach_i2c_device(dev, ps2smbus);
+	}
+
+	return 0;
+}
+
+static int ps2smbus_probe(struct platform_device *pdev)
+{
+	struct rmi_device_platform_data *rmi_pdata = pdev->dev.platform_data;
+	struct serio *parent;
+	struct ps2smbus *ps2smbus;
+	int error;
+
+	ps2smbus = devm_kzalloc(&pdev->dev, sizeof(struct ps2smbus),
+				GFP_KERNEL);
+	if (!ps2smbus)
+		return -ENOMEM;
+
+	ps2smbus->i2c_notifier.notifier_call = ps2smbus_notifier_call;
+	ps2smbus->pdata = pdev->dev.platform_data;
+	ps2smbus->type = pdev->id_entry->driver_data;
+	if (pdev->dev.parent) {
+		parent = to_serio_port(pdev->dev.parent);
+		if (ps2smbus->type == PS2SMBUS_SYNAPTICS_RMI4)
+			rmi_pdata->parent = parent;
+	}
+
+	/* Keep track of adapters which will be added or removed later */
+	error = bus_register_notifier(&i2c_bus_type, &ps2smbus->i2c_notifier);
+	if (error)
+		return error;
+
+	/* Bind to already existing adapters right away */
+	i2c_for_each_dev(ps2smbus, ps2smbus_attach_i2c_device);
+
+	platform_set_drvdata(pdev, ps2smbus);
+
+	return 0;
+}
+
+static int ps2smbus_remove(struct platform_device *pdev)
+{
+	struct ps2smbus *ps2smbus = platform_get_drvdata(pdev);
+
+	bus_unregister_notifier(&i2c_bus_type, &ps2smbus->i2c_notifier);
+
+	if (ps2smbus->smbus_client)
+		ps2smbus_schedule_work(PS2SMBUS_UNREGISTER_DEVICE, ps2smbus,
+				       NULL);
+
+	platform_set_drvdata(pdev, NULL);
+
+	return 0;
+}
+
+static const struct platform_device_id ps2smbus_id_table[] = {
+	{ .name = "rmi4", .driver_data = PS2SMBUS_SYNAPTICS_RMI4 },
+	{ }
+};
+MODULE_DEVICE_TABLE(platform, ps2smbus_id_table);
+
+static struct platform_driver ps2smbus_drv = {
+	.driver		= {
+		.name	= "ps2smbus",
+	},
+	.probe		= ps2smbus_probe,
+	.remove		= ps2smbus_remove,
+	.id_table	= ps2smbus_id_table,
+};
+
+static int __init ps2smbus_init(void)
+{
+	int err;
+
+	kps2smbus_wq = alloc_ordered_workqueue("kps2smbusd", WQ_MEM_RECLAIM);
+	if (!kps2smbus_wq) {
+		pr_err("failed to create kps2smbusd workqueue\n");
+		return -ENOMEM;
+	}
+
+	err = platform_driver_register(&ps2smbus_drv);
+	if (err)
+		destroy_workqueue(kps2smbus_wq);
+
+	return err;
+}
+
+static void __exit ps2smbus_exit(void)
+{
+	platform_driver_unregister(&ps2smbus_drv);
+	destroy_workqueue(kps2smbus_wq);
+}
+
+module_init(ps2smbus_init);
+module_exit(ps2smbus_exit);
diff --git a/drivers/input/rmi4/Kconfig b/drivers/input/rmi4/Kconfig
index 30cc627..eb74678 100644
--- a/drivers/input/rmi4/Kconfig
+++ b/drivers/input/rmi4/Kconfig
@@ -30,6 +30,7 @@ config RMI4_SPI
 config RMI4_SMB
 	tristate "RMI4 SMB Support"
 	depends on RMI4_CORE && I2C
+	select RMI4_PLATFORM
 	help
 	  Say Y here if you want to support RMI4 devices connected to an SMB
 	  bus.
-- 
2.9.3