Input: psmouse - add support for SMBus companions

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

The SMBus devices keep their PS/2 connection alive. If the initialization
process goes too far (psmouse_activate called), the device disconnects
from the I2C bus and stays on the PS/2 bus, that is why we explicitly
disable PS/2 device reporting (by calling psmouse_deactivate) before
trying to register SMBus companion device.

The HID over I2C devices are enumerated through the ACPI DSDT, and
their PS/2 device also exports the InterTouch bit in the extended
capability 0x0C. However, the firmware keeps its I2C connection open
even after going further in the PS/2 initialization. We don't need
to take extra precautions with those device, especially because they
block their PS/2 communication when HID over I2C is used.

Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

drivers/input/mouse/Kconfig

@@ -171,6 +171,10 @@ config MOUSE_PS2_VMMOUSE
 
 	  If unsure, say N.
 
+config MOUSE_PS2_SMBUS
+	bool
+	depends on MOUSE_PS2
+
 config MOUSE_SERIAL
 	tristate "Serial mouse"
 	select SERIO

drivers/input/mouse/Makefile

@@ -39,6 +39,8 @@ psmouse-$(CONFIG_MOUSE_PS2_TOUCHKIT)	+= touchkit_ps2.o
 psmouse-$(CONFIG_MOUSE_PS2_CYPRESS)	+= cypress_ps2.o
 psmouse-$(CONFIG_MOUSE_PS2_VMMOUSE)	+= vmmouse.o
 
+psmouse-$(CONFIG_MOUSE_PS2_SMBUS)	+= psmouse-smbus.o
+
 elan_i2c-objs := elan_i2c_core.o
 elan_i2c-$(CONFIG_MOUSE_ELAN_I2C_I2C)	+= elan_i2c_i2c.o
 elan_i2c-$(CONFIG_MOUSE_ELAN_I2C_SMBUS)	+= elan_i2c_smbus.o

drivers/input/mouse/psmouse-base.c

@@ -1999,16 +1999,27 @@ static int __init psmouse_init(void)
 	synaptics_module_init();
 	hgpk_module_init();
 
+	err = psmouse_smbus_module_init();
+	if (err)
+		return err;
+
 	kpsmoused_wq = alloc_ordered_workqueue("kpsmoused", 0);
 	if (!kpsmoused_wq) {
 		pr_err("failed to create kpsmoused workqueue\n");
-		return -ENOMEM;
+		err = -ENOMEM;
+		goto err_smbus_exit;
 	}
 
 	err = serio_register_driver(&psmouse_drv);
 	if (err)
-		destroy_workqueue(kpsmoused_wq);
+		goto err_destroy_wq;
 
+	return 0;
+
+err_destroy_wq:
+	destroy_workqueue(kpsmoused_wq);
+err_smbus_exit:
+	psmouse_smbus_module_exit();
 	return err;
 }
 
@@ -2016,6 +2027,7 @@ static void __exit psmouse_exit(void)
 {
 	serio_unregister_driver(&psmouse_drv);
 	destroy_workqueue(kpsmoused_wq);
+	psmouse_smbus_module_exit();
 }
 
 module_init(psmouse_init);

drivers/input/mouse/psmouse-smbus.c

@@ -0,0 +1,294 @@
+/*
+ * 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.
+ */
+
+#define pr_fmt(fmt)		KBUILD_MODNAME ": " fmt
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/libps2.h>
+#include <linux/i2c.h>
+#include <linux/serio.h>
+#include <linux/slab.h>
+#include <linux/workqueue.h>
+#include "psmouse.h"
+
+struct psmouse_smbus_dev {
+	struct i2c_board_info board;
+	struct psmouse *psmouse;
+	struct i2c_client *client;
+	struct list_head node;
+	bool dead;
+};
+
+static LIST_HEAD(psmouse_smbus_list);
+static DEFINE_MUTEX(psmouse_smbus_mutex);
+
+static void psmouse_smbus_check_adapter(struct i2c_adapter *adapter)
+{
+	struct psmouse_smbus_dev *smbdev;
+
+	if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_HOST_NOTIFY))
+		return;
+
+	mutex_lock(&psmouse_smbus_mutex);
+
+	list_for_each_entry(smbdev, &psmouse_smbus_list, node) {
+		if (smbdev->dead)
+			continue;
+
+		if (smbdev->client)
+			continue;
+
+		/*
+		 * Here would be a good place to check if device is actually
+		 * present, but it seems that SMBus will not respond unless we
+		 * fully reset PS/2 connection.  So cross our fingers, and try
+		 * to switch over, hopefully our system will not have too many
+		 * "host notify" I2C adapters.
+		 */
+		psmouse_dbg(smbdev->psmouse,
+			    "SMBus candidate adapter appeared, triggering rescan\n");
+		serio_rescan(smbdev->psmouse->ps2dev.serio);
+	}
+
+	mutex_unlock(&psmouse_smbus_mutex);
+}
+
+static void psmouse_smbus_detach_i2c_client(struct i2c_client *client)
+{
+	struct psmouse_smbus_dev *smbdev;
+
+	mutex_lock(&psmouse_smbus_mutex);
+
+	list_for_each_entry(smbdev, &psmouse_smbus_list, node) {
+		if (smbdev->client == client) {
+			psmouse_dbg(smbdev->psmouse,
+				    "Marking SMBus companion %s as gone\n",
+				    dev_name(&smbdev->client->dev));
+			smbdev->client = NULL;
+			smbdev->dead = true;
+			serio_rescan(smbdev->psmouse->ps2dev.serio);
+		}
+	}
+
+	kfree(client->dev.platform_data);
+	client->dev.platform_data = NULL;
+
+	mutex_unlock(&psmouse_smbus_mutex);
+}
+
+static int psmouse_smbus_notifier_call(struct notifier_block *nb,
+				       unsigned long action, void *data)
+{
+	struct device *dev = data;
+
+	switch (action) {
+	case BUS_NOTIFY_ADD_DEVICE:
+		if (dev->type == &i2c_adapter_type)
+			psmouse_smbus_check_adapter(to_i2c_adapter(dev));
+		break;
+
+	case BUS_NOTIFY_REMOVED_DEVICE:
+		if (dev->type != &i2c_adapter_type)
+			psmouse_smbus_detach_i2c_client(to_i2c_client(dev));
+		break;
+	}
+
+	return 0;
+}
+
+static struct notifier_block psmouse_smbus_notifier = {
+	.notifier_call = psmouse_smbus_notifier_call,
+};
+
+static psmouse_ret_t psmouse_smbus_process_byte(struct psmouse *psmouse)
+{
+	return PSMOUSE_FULL_PACKET;
+}
+
+static int psmouse_smbus_reconnect(struct psmouse *psmouse)
+{
+	psmouse_deactivate(psmouse);
+
+	return 0;
+}
+
+struct psmouse_smbus_removal_work {
+	struct work_struct work;
+	struct i2c_client *client;
+};
+
+static void psmouse_smbus_remove_i2c_device(struct work_struct *work)
+{
+	struct psmouse_smbus_removal_work *rwork =
+		container_of(work, struct psmouse_smbus_removal_work, work);
+
+	dev_dbg(&rwork->client->dev, "destroying SMBus companion device\n");
+	i2c_unregister_device(rwork->client);
+
+	kfree(rwork);
+}
+
+/*
+ * This schedules removal of SMBus companion device. We have to do
+ * it in a separate tread to avoid deadlocking on psmouse_mutex in
+ * case the device has a trackstick (which is also driven by psmouse).
+ *
+ * Note that this may be racing with i2c adapter removal, but we
+ * can't do anything about that: i2c automatically destroys clients
+ * attached to an adapter that is being removed. This has to be
+ * fixed in i2c core.
+ */
+static void psmouse_smbus_schedule_remove(struct i2c_client *client)
+{
+	struct psmouse_smbus_removal_work *rwork;
+
+	rwork = kzalloc(sizeof(*rwork), GFP_KERNEL);
+	if (rwork) {
+		INIT_WORK(&rwork->work, psmouse_smbus_remove_i2c_device);
+		rwork->client = client;
+
+		schedule_work(&rwork->work);
+	}
+}
+
+static void psmouse_smbus_disconnect(struct psmouse *psmouse)
+{
+	struct psmouse_smbus_dev *smbdev = psmouse->private;
+
+	mutex_lock(&psmouse_smbus_mutex);
+	list_del(&smbdev->node);
+	mutex_unlock(&psmouse_smbus_mutex);
+
+	if (smbdev->client) {
+		psmouse_dbg(smbdev->psmouse,
+			    "posting removal request for SMBus companion %s\n",
+			    dev_name(&smbdev->client->dev));
+		psmouse_smbus_schedule_remove(smbdev->client);
+	}
+
+	kfree(smbdev);
+	psmouse->private = NULL;
+}
+
+static int psmouse_smbus_create_companion(struct device *dev, void *data)
+{
+	struct psmouse_smbus_dev *smbdev = data;
+	unsigned short addr_list[] = { smbdev->board.addr, I2C_CLIENT_END };
+	struct i2c_adapter *adapter;
+
+	adapter = i2c_verify_adapter(dev);
+	if (!adapter)
+		return 0;
+
+	if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_HOST_NOTIFY))
+		return 0;
+
+	smbdev->client = i2c_new_probed_device(adapter, &smbdev->board,
+					       addr_list, NULL);
+	if (!smbdev->client)
+		return 0;
+
+	/* We have our(?) device, stop iterating i2c bus. */
+	return 1;
+}
+
+void psmouse_smbus_cleanup(struct psmouse *psmouse)
+{
+	struct psmouse_smbus_dev *smbdev, *tmp;
+
+	mutex_lock(&psmouse_smbus_mutex);
+
+	list_for_each_entry_safe(smbdev, tmp, &psmouse_smbus_list, node) {
+		if (psmouse == smbdev->psmouse) {
+			list_del(&smbdev->node);
+			kfree(smbdev);
+		}
+	}
+
+	mutex_unlock(&psmouse_smbus_mutex);
+}
+
+int psmouse_smbus_init(struct psmouse *psmouse,
+		       const struct i2c_board_info *board,
+		       const void *pdata, size_t pdata_size,
+		       bool leave_breadcrumbs)
+{
+	struct psmouse_smbus_dev *smbdev;
+	int error;
+
+	smbdev = kzalloc(sizeof(*smbdev), GFP_KERNEL);
+	if (!smbdev)
+		return -ENOMEM;
+
+	smbdev->psmouse = psmouse;
+	smbdev->board = *board;
+
+	smbdev->board.platform_data = kmemdup(pdata, pdata_size, GFP_KERNEL);
+	if (!smbdev->board.platform_data) {
+		kfree(smbdev);
+		return -ENOMEM;
+	}
+
+	psmouse->private = smbdev;
+	psmouse->protocol_handler = psmouse_smbus_process_byte;
+	psmouse->reconnect = psmouse_smbus_reconnect;
+	psmouse->fast_reconnect = psmouse_smbus_reconnect;
+	psmouse->disconnect = psmouse_smbus_disconnect;
+	psmouse->resync_time = 0;
+
+	psmouse_deactivate(psmouse);
+
+	mutex_lock(&psmouse_smbus_mutex);
+	list_add_tail(&smbdev->node, &psmouse_smbus_list);
+	mutex_unlock(&psmouse_smbus_mutex);
+
+	/* Bind to already existing adapters right away */
+	error = i2c_for_each_dev(smbdev, psmouse_smbus_create_companion);
+
+	if (smbdev->client) {
+		/* We have our companion device */
+		return 0;
+	}
+
+	/*
+	 * If we did not create i2c device we will not need platform
+	 * data even if we are leaving breadcrumbs.
+	 */
+	kfree(smbdev->board.platform_data);
+	smbdev->board.platform_data = NULL;
+
+	if (error < 0 || !leave_breadcrumbs) {
+		mutex_lock(&psmouse_smbus_mutex);
+		list_del(&smbdev->node);
+		mutex_unlock(&psmouse_smbus_mutex);
+
+		kfree(smbdev);
+	}
+
+	return error < 0 ? error : -EAGAIN;
+}
+
+int __init psmouse_smbus_module_init(void)
+{
+	int error;
+
+	error = bus_register_notifier(&i2c_bus_type, &psmouse_smbus_notifier);
+	if (error) {
+		pr_err("failed to register i2c bus notifier: %d\n", error);
+		return error;
+	}
+
+	return 0;
+}
+
+void psmouse_smbus_module_exit(void)
+{
+	bus_unregister_notifier(&i2c_bus_type, &psmouse_smbus_notifier);
+	flush_scheduled_work();
+}

drivers/input/mouse/psmouse.h

@@ -209,5 +209,34 @@ static struct psmouse_attribute psmouse_attr_##_name = {			\
 		   &(psmouse)->ps2dev.serio->dev,	\
 		   psmouse_fmt(format), ##__VA_ARGS__)
 
+#ifdef CONFIG_MOUSE_PS2_SMBUS
+
+int psmouse_smbus_module_init(void);
+void psmouse_smbus_module_exit(void);
+
+struct i2c_board_info;
+
+int psmouse_smbus_init(struct psmouse *psmouse,
+		       const struct i2c_board_info *board,
+		       const void *pdata, size_t pdata_size,
+		       bool leave_breadcrumbs);
+void psmouse_smbus_cleanup(struct psmouse *psmouse);
+
+#else /* !CONFIG_MOUSE_PS2_SMBUS */
+
+static inline int psmouse_smbus_module_init(void)
+{
+	return 0;
+}
+
+static inline void psmouse_smbus_module_exit(void)
+{
+}
+
+static inline void psmouse_smbus_cleanup(struct psmouse *psmouse)
+{
+}
+
+#endif /* CONFIG_MOUSE_PS2_SMBUS */
 
 #endif /* _PSMOUSE_H */