Date:   Fri, 31 Mar 2017 11:37:05 +0200
From:   Benjamin Tissoires <benjamin.tissoires@...hat.com>
To:     Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:     Andrew Duggan <aduggan@...aptics.com>,
        linux-kernel@...r.kernel.org, linux-input@...r.kernel.org
Subject: Re: [PATCH v2 6/9] Input: psmouse - add support for SMBus companions

Hi Dmitry,

On Mar 10 2017 or thereabouts, Dmitry Torokhov wrote:
> From: Benjamin Tissoires <benjamin.tissoires@...hat.com>
> 
> 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@...hat.com>
> Signed-off-by: Dmitry Torokhov <dmitry.torokhov@...il.com>
> ---
>  drivers/input/mouse/Kconfig         |   4 +
>  drivers/input/mouse/Makefile        |   2 +
>  drivers/input/mouse/psmouse-base.c  |  16 +-
>  drivers/input/mouse/psmouse-smbus.c | 291 ++++++++++++++++++++++++++++++++++++
>  drivers/input/mouse/psmouse.h       |  37 +++++
>  5 files changed, 348 insertions(+), 2 deletions(-)
>  create mode 100644 drivers/input/mouse/psmouse-smbus.c
> 
> diff --git a/drivers/input/mouse/Kconfig b/drivers/input/mouse/Kconfig
> index 096abb4ad5cd..87bde8a210c7 100644
> --- a/drivers/input/mouse/Kconfig
> +++ b/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
> diff --git a/drivers/input/mouse/Makefile b/drivers/input/mouse/Makefile
> index 6168b134937b..56bf0ad877c6 100644
> --- a/drivers/input/mouse/Makefile
> +++ b/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
> diff --git a/drivers/input/mouse/psmouse-base.c b/drivers/input/mouse/psmouse-base.c
> index 40f09ce84f14..bdb48b2acc57 100644
> --- a/drivers/input/mouse/psmouse-base.c
> +++ b/drivers/input/mouse/psmouse-base.c
> @@ -1996,16 +1996,27 @@ 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;
>  }
>  
> @@ -2013,6 +2024,7 @@ static void __exit psmouse_exit(void)
>  {
>  	serio_unregister_driver(&psmouse_drv);
>  	destroy_workqueue(kpsmoused_wq);
> +	psmouse_smbus_module_exit();
>  }
>  
>  module_init(psmouse_init);
> diff --git a/drivers/input/mouse/psmouse-smbus.c b/drivers/input/mouse/psmouse-smbus.c
> new file mode 100644
> index 000000000000..cc716977fbf9
> --- /dev/null
> +++ b/drivers/input/mouse/psmouse-smbus.c
> @@ -0,0 +1,291 @@
> +/*
> + * 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;
> +
> +		if (i2c_probe_func_quick_read(adapter, smbdev->board.addr) < 0)
> +			continue;
> +
> +		/* Device seems to be there, let's try switching over */
> +		psmouse_dbg(smbdev->psmouse,
> +			    "SMBus companion 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;

I realized (thanks to an oops) that this is a little bit too much :)

We are freeing whatever platform_data for *all* I2C devices :/

I would say the following patch should be working, but I haven't spent too
much time on it yet:

---

diff --git a/drivers/input/mouse/psmouse-smbus.c b/drivers/input/mouse/psmouse-smbus.c
index 061c1cc..b77263e 100644
--- a/drivers/input/mouse/psmouse-smbus.c
+++ b/drivers/input/mouse/psmouse-smbus.c
@@ -61,24 +61,30 @@ static void psmouse_smbus_check_adapter(struct i2c_adapter *adapter)
 
 static void psmouse_smbus_detach_i2c_client(struct i2c_client *client)
 {
-	struct psmouse_smbus_dev *smbdev;
+	struct psmouse_smbus_dev *smbdev, *tmp;
 
 	mutex_lock(&psmouse_smbus_mutex);
 
-	list_for_each_entry(smbdev, &psmouse_smbus_list, node) {
+	list_for_each_entry_safe(smbdev, tmp, &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;
+
+			kfree(client->dev.platform_data);
+			client->dev.platform_data = NULL;
+
+			mutex_lock(&psmouse_smbus_mutex);
+			list_del(&smbdev->node);
+			mutex_unlock(&psmouse_smbus_mutex);
+
+			kfree(smbdev);
 			serio_rescan(smbdev->psmouse->ps2dev.serio);
 		}
 	}
 
-	kfree(client->dev.platform_data);
-	client->dev.platform_data = NULL;
-
 	mutex_unlock(&psmouse_smbus_mutex);
 }
 
@@ -161,17 +167,19 @@ 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);
+		psmouse->private = NULL;
+		return;
 	}
 
+	mutex_lock(&psmouse_smbus_mutex);
+	list_del(&smbdev->node);
+	mutex_unlock(&psmouse_smbus_mutex);
+
 	kfree(smbdev);
 	psmouse->private = NULL;
 }

---

I am just dumping my diff that seems to be OK here. Feel free to
integrate in a proper patch or wait next week for a more formal
submission from me.


Cheers,
Benjamin

> +
> +	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_client_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 __exit psmouse_smbus_module_exit(void)
> +{
> +	bus_unregister_notifier(&i2c_bus_type, &psmouse_smbus_notifier);
> +	flush_scheduled_work();
> +}
> diff --git a/drivers/input/mouse/psmouse.h b/drivers/input/mouse/psmouse.h
> index e853dee05e79..77fcd361c8d6 100644
> --- a/drivers/input/mouse/psmouse.h
> +++ b/drivers/input/mouse/psmouse.h
> @@ -209,5 +209,42 @@ 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)
> +{
> +}
> +
> +int psmouse_smbus_init(struct psmouse *psmouse,
> +		       const struct i2c_board_info *board,
> +		       const void *pdata, size_t pdata_size,
> +		       bool leave_breadcrumbs)
> +{
> +	return -ENOSYS;
> +}
> +
> +void psmouse_smbus_cleanup(struct psmouse *psmouse)
> +{
> +}
> +
> +#endif /* CONFIG_MOUSE_PS2_SMBUS */
>  
>  #endif /* _PSMOUSE_H */
> -- 
> 2.12.0.246.ga2ecc84866-goog
> 

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