[PATCH v2 3/3] 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>

---

changes in v2:
- use our own ps2 driver (detach psmouse and reattach ours)
---
 drivers/input/misc/Kconfig     |  11 ++
 drivers/input/misc/Makefile    |   1 +
 drivers/input/misc/ps2_smbus.c | 382 +++++++++++++++++++++++++++++++++++++++++
 drivers/input/rmi4/Kconfig     |   1 +
 4 files changed, 395 insertions(+)
 create mode 100644 drivers/input/misc/ps2_smbus.c

diff --git a/drivers/input/misc/Kconfig b/drivers/input/misc/Kconfig
index 5b6c522..64362ba 100644
--- a/drivers/input/misc/Kconfig
+++ b/drivers/input/misc/Kconfig
@@ -822,4 +822,15 @@ 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 b10523f..59406da 100644
--- a/drivers/input/misc/Makefile
+++ b/drivers/input/misc/Makefile
@@ -56,6 +56,7 @@ 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..b58c113
--- /dev/null
+++ b/drivers/input/misc/ps2_smbus.c
@@ -0,0 +1,382 @@
+/*
+ * 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/libps2.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;
+static DECLARE_WAIT_QUEUE_HEAD(ps2smbus_serio_wait);
+static DEFINE_MUTEX(ps2smbus_mutex);
+
+enum ps2smbus_type {
+	PS2SMBUS_SYNAPTICS_RMI4,
+};
+
+struct ps2smbus {
+	struct serio *serio;
+	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;
+};
+
+struct ps2smbus_serio {
+	struct ps2dev ps2dev;
+};
+
+static struct serio_device_id ps2smbus_serio_ids[] = {
+	{
+		.type	= SERIO_8042,
+		.proto	= SERIO_ANY,
+		.id	= SERIO_ANY,
+		.extra	= SERIO_ANY,
+	},
+	{ 0 }
+};
+
+MODULE_DEVICE_TABLE(serio, ps2smbus_serio_ids);
+
+static irqreturn_t ps2smbus_interrupt(struct serio *serio,
+		unsigned char data, unsigned int flags)
+{
+	struct ps2smbus_serio *ps2smbus = serio_get_drvdata(serio);
+
+	if (unlikely((flags & SERIO_TIMEOUT) || (flags & SERIO_PARITY))) {
+		ps2_cmd_aborted(&ps2smbus->ps2dev);
+		goto out;
+	}
+
+	if (unlikely(ps2smbus->ps2dev.flags & PS2_FLAG_ACK))
+		if (ps2_handle_ack(&ps2smbus->ps2dev, data))
+			goto out;
+
+	if (unlikely(ps2smbus->ps2dev.flags & PS2_FLAG_CMD))
+		if (ps2_handle_response(&ps2smbus->ps2dev, data))
+			goto out;
+
+out:
+	return IRQ_HANDLED;
+}
+
+#define PSMOUSE_CMD_DISABLE	0x00f5
+
+static int ps2smbus_connect(struct serio *serio, struct serio_driver *drv)
+{
+	int error;
+	struct ps2smbus_serio *ps2smbus;
+
+	ps2smbus = kzalloc(sizeof(struct ps2smbus_serio), GFP_KERNEL);
+
+	ps2_init(&ps2smbus->ps2dev, serio);
+
+	serio_set_drvdata(serio, ps2smbus);
+
+	error = serio_open(serio, drv);
+	if (error)
+		goto fail_free;
+
+	error = ps2_command(&ps2smbus->ps2dev, NULL, PSMOUSE_CMD_DISABLE);
+	if (error) {
+		dev_warn(&serio->dev, "Failed to deactivate mouse on %s\n",
+			 serio->phys);
+		goto fail;
+	}
+
+	wake_up_interruptible(&ps2smbus_serio_wait);
+
+	return 0;
+
+fail:
+	serio_close(serio);
+fail_free:
+	serio_set_drvdata(serio, NULL);
+	kfree(ps2smbus);
+	return error;
+}
+
+static int ps2smbus_reconnect(struct serio *serio)
+{
+	return 0;
+}
+
+static void ps2smbus_disconnect(struct serio *serio)
+{
+	struct ps2smbus_serio *ps2smbus = serio_get_drvdata(serio);
+
+	serio_clear_manual_driver(serio);
+	serio_close(serio);
+	serio_set_drvdata(serio, NULL);
+	kfree(ps2smbus);
+}
+
+static struct serio_driver ps2smbus_serio_drv = {
+	.driver		= {
+		.name	= "ps2smbus",
+	},
+	.description	= "PS/2 SMBus bridge",
+	.id_table	= ps2smbus_serio_ids,
+	.interrupt	= ps2smbus_interrupt,
+	.connect	= ps2smbus_connect,
+	.reconnect	= ps2smbus_reconnect,
+	.disconnect	= ps2smbus_disconnect,
+	.manual_bind	= true,
+};
+
+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;
+	struct serio *serio;
+	int error;
+
+	ps2smbus_work = container_of(work, struct ps2smbus_work, work);
+	client = ps2smbus_work->ps2smbus->smbus_client;
+	serio = ps2smbus_work->ps2smbus->serio;
+
+	mutex_lock(&ps2smbus_mutex);
+
+	switch (ps2smbus_work->type) {
+	case PS2SMBUS_REGISTER_DEVICE:
+		serio_bind_manual_driver(serio, &ps2smbus_serio_drv);
+		error = wait_event_interruptible_timeout(ps2smbus_serio_wait,
+				serio->drv == &ps2smbus_serio_drv,
+				msecs_to_jiffies(2000));
+		if (error <= 1) {
+			dev_warn(&serio->dev,
+				 "error while waiting for the PS/2 node to be ready: %d\n",
+				 error);
+			goto out;
+		}
+
+		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;
+	}
+
+out:
+	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 ps2smbus *ps2smbus;
+	int error;
+
+	if (!pdev->dev.parent)
+		return -EINVAL;
+
+	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;
+	ps2smbus->serio = to_serio_port(pdev->dev.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);
+
+	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;
+
+	err = serio_register_driver(&ps2smbus_serio_drv);
+	if (err)
+		return err;
+
+	kps2smbus_wq = alloc_ordered_workqueue("kps2smbusd", WQ_MEM_RECLAIM);
+	if (!kps2smbus_wq) {
+		pr_err("failed to create kps2smbusd workqueue\n");
+		err = -ENOMEM;
+		goto fail_workqueue;
+	}
+
+	err = platform_driver_register(&ps2smbus_drv);
+	if (err)
+		goto fail_register_pdrv;
+
+	return 0;
+
+fail_register_pdrv:
+	destroy_workqueue(kps2smbus_wq);
+fail_workqueue:
+	serio_unregister_driver(&ps2smbus_serio_drv);
+	return err;
+}
+
+static void __exit ps2smbus_exit(void)
+{
+	platform_driver_unregister(&ps2smbus_drv);
+	destroy_workqueue(kps2smbus_wq);
+	serio_unregister_driver(&ps2smbus_serio_drv);
+}
+
+module_init(ps2smbus_init);
+module_exit(ps2smbus_exit);
diff --git a/drivers/input/rmi4/Kconfig b/drivers/input/rmi4/Kconfig
index 7341bf0..6c067f7 100644
--- a/drivers/input/rmi4/Kconfig
+++ b/drivers/input/rmi4/Kconfig
@@ -32,6 +32,7 @@ config RMI4_SPI
 config RMI4_SMB
 	tristate "RMI4 SMB Support"
 	depends on I2C
+	select PS2_SMBUS
 	help
 	  Say Y here if you want to support RMI4 devices connected to an SMB
 	  bus.
-- 
2.9.3