[PATCH 2/2] HID: google: add Whiskers driver to handle tablet mode properly

[Dmitry Torokhov <dtor@chromium.org>]

This adds dedicated "Whiskers" driver that hooks both into HID and EC to
produce proper SW_TABLET_SWITCH event from base presence bit from EC and
base state (folded/unfolded) coming from USB/HID.

Signed-off-by: Nicolas Boichat <drinkcat@chromium.org>
Signed-off-by: Dmitry Torokhov <dtor@chromium.org>
---
 drivers/hid/Kconfig               |   6 +
 drivers/hid/Makefile              |   1 +
 drivers/hid/hid-google-hammer.c   |   7 +-
 drivers/hid/hid-google-whiskers.c | 382 ++++++++++++++++++++++++++++++
 4 files changed, 392 insertions(+), 4 deletions(-)
 create mode 100644 drivers/hid/hid-google-whiskers.c

diff --git a/drivers/hid/Kconfig b/drivers/hid/Kconfig
index e5ec47705fa2..0607f1c7129e 100644
--- a/drivers/hid/Kconfig
+++ b/drivers/hid/Kconfig
@@ -355,6 +355,12 @@ config HID_GOOGLE_HAMMER
 	---help---
 	Say Y here if you have a Google Hammer device.
 
+config HID_GOOGLE_WHISKERS
+	tristate "Google Whiskers Keyboard"
+	depends on HID_GOOGLE_HAMMER && MFD_CROS_EC
+	---help---
+	Say Y here if you have a Google Whiskers device.
+
 config HID_GT683R
 	tristate "MSI GT68xR LED support"
 	depends on LEDS_CLASS && USB_HID
diff --git a/drivers/hid/Makefile b/drivers/hid/Makefile
index bd7ac53b75c5..241e583b6913 100644
--- a/drivers/hid/Makefile
+++ b/drivers/hid/Makefile
@@ -47,6 +47,7 @@ obj-$(CONFIG_HID_EZKEY)		+= hid-ezkey.o
 obj-$(CONFIG_HID_GEMBIRD)	+= hid-gembird.o
 obj-$(CONFIG_HID_GFRM)		+= hid-gfrm.o
 obj-$(CONFIG_HID_GOOGLE_HAMMER)	+= hid-google-hammer.o
+obj-$(CONFIG_HID_GOOGLE_WHISKERS)	+= hid-google-whiskers.o
 obj-$(CONFIG_HID_GT683R)	+= hid-gt683r.o
 obj-$(CONFIG_HID_GYRATION)	+= hid-gyration.o
 obj-$(CONFIG_HID_HOLTEK)	+= hid-holtek-kbd.o
diff --git a/drivers/hid/hid-google-hammer.c b/drivers/hid/hid-google-hammer.c
index 6bf4da7ad63a..81ddf9773df9 100644
--- a/drivers/hid/hid-google-hammer.c
+++ b/drivers/hid/hid-google-hammer.c
@@ -18,6 +18,7 @@
 #include <linux/module.h>
 
 #include "hid-ids.h"
+#include "hid-google-hammer.h"
 
 #define MAX_BRIGHTNESS 100
 
@@ -90,8 +91,7 @@ static int hammer_register_leds(struct hid_device *hdev)
 	return devm_led_classdev_register(&hdev->dev, &kbd_backlight->cdev);
 }
 
-static int hammer_input_configured(struct hid_device *hdev,
-				   struct hid_input *hi)
+int hammer_input_configured(struct hid_device *hdev, struct hid_input *hi)
 {
 	struct list_head *report_list =
 		&hdev->report_enum[HID_OUTPUT_REPORT].report_list;
@@ -116,6 +116,7 @@ static int hammer_input_configured(struct hid_device *hdev,
 
 	return 0;
 }
+EXPORT_SYMBOL_GPL(hammer_input_configured);
 
 static const struct hid_device_id hammer_devices[] = {
 	{ HID_DEVICE(BUS_USB, HID_GROUP_GENERIC,
@@ -124,8 +125,6 @@ static const struct hid_device_id hammer_devices[] = {
 		     USB_VENDOR_ID_GOOGLE, USB_DEVICE_ID_GOOGLE_STAFF) },
 	{ HID_DEVICE(BUS_USB, HID_GROUP_GENERIC,
 		     USB_VENDOR_ID_GOOGLE, USB_DEVICE_ID_GOOGLE_WAND) },
-	{ HID_DEVICE(BUS_USB, HID_GROUP_GENERIC,
-		     USB_VENDOR_ID_GOOGLE, USB_DEVICE_ID_GOOGLE_WHISKERS) },
 	{ }
 };
 MODULE_DEVICE_TABLE(hid, hammer_devices);
diff --git a/drivers/hid/hid-google-whiskers.c b/drivers/hid/hid-google-whiskers.c
new file mode 100644
index 000000000000..ff3d2bfa1194
--- /dev/null
+++ b/drivers/hid/hid-google-whiskers.c
@@ -0,0 +1,382 @@
+// SPDX-License-Identifier: GPL-2.0+
+//
+// HID driver for Google Whiskers device.
+//
+// Copyright (c) 2018 Google Inc.
+
+#include <linux/acpi.h>
+#include <linux/hid.h>
+#include <linux/leds.h>
+#include <linux/mfd/cros_ec.h>
+#include <linux/mfd/cros_ec_commands.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/pm_wakeup.h>
+#include <linux/usb.h>
+#include <asm/unaligned.h>
+
+#include "hid-ids.h"
+#include "hid-google-hammer.h"
+
+#define HID_UP_GOOGLEVENDOR	0xffd10000
+#define HID_VD_KBD_FOLDED	0x00000019
+#define WHISKERS_KBD_FOLDED	(HID_UP_GOOGLEVENDOR | HID_VD_KBD_FOLDED)
+
+struct whiskers_ec {
+	struct device *dev;	/* The platform device (EC) */
+	struct input_dev *input;
+	bool base_present;
+	struct notifier_block notifier;
+};
+
+static struct whiskers_ec whiskers_ec;
+static DEFINE_SPINLOCK(whiskers_ec_lock);
+static DEFINE_MUTEX(whiskers_ec_reglock);
+
+static bool whiskers_parse_base_state(const void *data)
+{
+	u32 switches = get_unaligned_le32(data);
+
+	return !!(switches & BIT(EC_MKBP_BASE_ATTACHED));
+}
+
+static int whiskers_ec_query_base(struct cros_ec_device *ec_dev, bool get_state,
+				  bool *state)
+{
+	struct ec_params_mkbp_info *params;
+	struct cros_ec_command *msg;
+	int ret;
+
+	msg = kzalloc(sizeof(*msg) + max(sizeof(u32), sizeof(*params)),
+		      GFP_KERNEL);
+	if (!msg)
+		return -ENOMEM;
+
+	msg->command = EC_CMD_MKBP_INFO;
+	msg->version = 1;
+	msg->outsize = sizeof(*params);
+	msg->insize = sizeof(u32);
+	params = (struct ec_params_mkbp_info *)msg->data;
+	params->info_type = get_state ?
+		EC_MKBP_INFO_CURRENT : EC_MKBP_INFO_SUPPORTED;
+	params->event_type = EC_MKBP_EVENT_SWITCH;
+
+	ret = cros_ec_cmd_xfer_status(ec_dev, msg);
+	if (ret >= 0) {
+		if (ret != sizeof(u32)) {
+			dev_warn(ec_dev->dev, "wrong result size: %d != %zu\n",
+				 ret, sizeof(u32));
+			ret = -EPROTO;
+		} else {
+			*state = whiskers_parse_base_state(msg->data);
+			ret = 0;
+		}
+	}
+
+	kfree(msg);
+
+	return ret;
+}
+
+static int whiskers_ec_notify(struct notifier_block *nb,
+			      unsigned long queued_during_suspend,
+			      void *_notify)
+{
+	struct cros_ec_device *ec = _notify;
+	unsigned long flags;
+	bool base_present;
+
+	if (ec->event_data.event_type == EC_MKBP_EVENT_SWITCH) {
+		base_present = whiskers_parse_base_state(
+					&ec->event_data.data.switches);
+		dev_dbg(whiskers_ec.dev,
+			"%s: base: %d\n", __func__, base_present);
+
+		if (device_may_wakeup(whiskers_ec.dev) ||
+		    !queued_during_suspend) {
+
+			pm_wakeup_event(whiskers_ec.dev, 0);
+
+			spin_lock_irqsave(&whiskers_ec_lock, flags);
+
+			/*
+			 * While input layer dedupes the events, we do not want
+			 * to disrupt the state reported by the base by
+			 * overriding it with state reported by the LID. Only
+			 * report changes, as we assume that on attach the base
+			 * is not folded.
+			 */
+			if (base_present != whiskers_ec.base_present) {
+				input_report_switch(whiskers_ec.input,
+						    SW_TABLET_MODE,
+						    !base_present);
+				input_sync(whiskers_ec.input);
+				whiskers_ec.base_present = base_present;
+			}
+
+			spin_unlock_irqrestore(&whiskers_ec_lock, flags);
+		}
+	}
+
+	return NOTIFY_OK;
+}
+
+static __maybe_unused int whiskers_ec_resume(struct device *dev)
+{
+	struct cros_ec_device *ec = dev_get_drvdata(dev->parent);
+	bool base_present;
+	int error;
+
+	error = whiskers_ec_query_base(ec, true, &base_present);
+	if (error) {
+		dev_warn(dev, "failed to fetch base state on resume: %d\n",
+			 error);
+	} else {
+		spin_lock_irq(&whiskers_ec_lock);
+
+		whiskers_ec.base_present = base_present;
+
+		/*
+		 * Only report if base is disconnected. If base is connected,
+		 * it will resend its state on resume, and we'll update it
+		 * in whiskers_event().
+		 */
+		if (!whiskers_ec.base_present) {
+			input_report_switch(whiskers_ec.input,
+					    SW_TABLET_MODE, 1);
+			input_sync(whiskers_ec.input);
+		}
+
+		spin_unlock_irq(&whiskers_ec_lock);
+	}
+
+	return 0;
+}
+
+static SIMPLE_DEV_PM_OPS(whiskers_ec_pm_ops, NULL, whiskers_ec_resume);
+
+static void whiskers_ec_set_input(struct input_dev *input)
+{
+	/* Take the lock so whiskers_event does not race with us here */
+	spin_lock_irq(&whiskers_ec_lock);
+	whiskers_ec.input = input;
+	spin_unlock_irq(&whiskers_ec_lock);
+}
+
+static int __whiskers_ec_probe(struct platform_device *pdev)
+{
+	struct cros_ec_device *ec = dev_get_drvdata(pdev->dev.parent);
+	struct input_dev *input;
+	bool base_supported;
+	int error;
+
+	error = whiskers_ec_query_base(ec, false, &base_supported);
+	if (error)
+		return error;
+
+	if (!base_supported)
+		return -ENXIO;
+
+	input = devm_input_allocate_device(&pdev->dev);
+	if (!input)
+		return -ENOMEM;
+
+	input->name = "Whiskers Tablet Mode Switch";
+
+	input->id.bustype = BUS_HOST;
+	input->id.version = 1;
+	input->id.product = 0;
+
+	input_set_capability(input, EV_SW, SW_TABLET_MODE);
+
+	error = input_register_device(input);
+	if (error) {
+		dev_err(&pdev->dev, "cannot register input device: %d\n",
+			error);
+		return error;
+	}
+
+	/* Seed the state */
+	error = whiskers_ec_query_base(ec, true, &whiskers_ec.base_present);
+	if (error) {
+		dev_err(&pdev->dev, "cannot query base state: %d\n", error);
+		return error;
+	}
+
+	input_report_switch(input, SW_TABLET_MODE, !whiskers_ec.base_present);
+
+	whiskers_ec_set_input(input);
+
+	whiskers_ec.dev = &pdev->dev;
+	whiskers_ec.notifier.notifier_call = whiskers_ec_notify;
+	error = blocking_notifier_chain_register(&ec->event_notifier,
+						 &whiskers_ec.notifier);
+	if (error) {
+		dev_err(&pdev->dev, "cannot register notifier: %d\n", error);
+		whiskers_ec_set_input(NULL);
+		return error;
+	}
+
+	device_init_wakeup(&pdev->dev, true);
+	return 0;
+}
+
+static int whiskers_ec_probe(struct platform_device *pdev)
+{
+	int retval;
+
+	mutex_lock(&whiskers_ec_reglock);
+
+	if (whiskers_ec.input) {
+		retval = -EBUSY;
+		goto out;
+	}
+
+	retval = __whiskers_ec_probe(pdev);
+
+out:
+	mutex_unlock(&whiskers_ec_reglock);
+	return retval;
+}
+
+static int whiskers_ec_remove(struct platform_device *pdev)
+{
+	struct cros_ec_device *ec = dev_get_drvdata(pdev->dev.parent);
+
+	mutex_lock(&whiskers_ec_reglock);
+
+	blocking_notifier_chain_unregister(&ec->event_notifier,
+					   &whiskers_ec.notifier);
+	whiskers_ec_set_input(NULL);
+
+	mutex_unlock(&whiskers_ec_reglock);
+	return 0;
+}
+
+static const struct acpi_device_id whiskers_ec_acpi_ids[] = {
+	{ "GOOG000B", 0 },
+	{ }
+};
+MODULE_DEVICE_TABLE(acpi, whiskers_ec_acpi_ids);
+
+static struct platform_driver whiskers_ec_driver = {
+	.probe	= whiskers_ec_probe,
+	.remove	= whiskers_ec_remove,
+	.driver	= {
+		.name			= "whiskers_ec",
+		.acpi_match_table	= ACPI_PTR(whiskers_ec_acpi_ids),
+		.pm			= &whiskers_ec_pm_ops,
+	},
+};
+
+static int whiskers_input_mapping(struct hid_device *hdev, struct hid_input *hi,
+				  struct hid_field *field,
+				  struct hid_usage *usage,
+				  unsigned long **bit, int *max)
+{
+	if (usage->hid == WHISKERS_KBD_FOLDED) {
+		/*
+		 * We do not want to have this usage mapped as it will get
+		 * mixed in with "base attached" signal and delivered over
+		 * separate input device for tablet switch mode.
+		 */
+
+		return -1;
+	}
+
+	return 0;
+}
+
+static int whiskers_event(struct hid_device *hid, struct hid_field *field,
+			  struct hid_usage *usage, __s32 value)
+{
+	unsigned long flags;
+
+	if (usage->hid == WHISKERS_KBD_FOLDED) {
+		spin_lock_irqsave(&whiskers_ec_lock, flags);
+
+		hid_dbg(hid, "%s: base: %d, folded: %d\n", __func__,
+			whiskers_ec.base_present, value);
+
+		/*
+		 * We should not get event if base is detached, but in case
+		 * we happen to service HID and EC notifications out of order
+		 * let's still check the "base present" flag.
+		 */
+		if (whiskers_ec.input && whiskers_ec.base_present) {
+			input_report_switch(whiskers_ec.input,
+					    SW_TABLET_MODE, value);
+			input_sync(whiskers_ec.input);
+		}
+
+		spin_unlock_irqrestore(&whiskers_ec_lock, flags);
+		return 1; /* We handled this event */
+	}
+
+	return 0;
+}
+
+static int whiskers_probe(struct hid_device *hdev,
+			  const struct hid_device_id *id)
+{
+	struct usb_interface *intf = to_usb_interface(hdev->dev.parent);
+	int ret;
+
+	/*
+	 * We always want to poll for, and handle tablet mode events, even when
+	 * nobody has opened the input device. This also prevents the hid core
+	 * from dropping early tablet mode events from the device.
+	 */
+	if (intf->cur_altsetting->desc.bInterfaceProtocol ==
+			USB_INTERFACE_PROTOCOL_KEYBOARD)
+		hdev->quirks |= HID_QUIRK_ALWAYS_POLL;
+
+	ret = hid_parse(hdev);
+	if (!ret)
+		ret = hid_hw_start(hdev, HID_CONNECT_DEFAULT);
+
+	return ret;
+}
+
+static const struct hid_device_id whiskers_hid_devices[] = {
+	{ HID_DEVICE(BUS_USB, HID_GROUP_GENERIC,
+		     USB_VENDOR_ID_GOOGLE, USB_DEVICE_ID_GOOGLE_WHISKERS) },
+	{ }
+};
+MODULE_DEVICE_TABLE(hid, whiskers_hid_devices);
+
+static struct hid_driver whiskers_hid_driver = {
+	.name			= "whiskers",
+	.id_table		= whiskers_hid_devices,
+	.probe			= whiskers_probe,
+	.input_configured	= hammer_input_configured,
+	.input_mapping		= whiskers_input_mapping,
+	.event			= whiskers_event,
+};
+
+static int __init whiskers_init(void)
+{
+	int error;
+
+	error = platform_driver_register(&whiskers_ec_driver);
+	if (error)
+		return error;
+
+	error = hid_register_driver(&whiskers_hid_driver);
+	if (error) {
+		platform_driver_unregister(&whiskers_ec_driver);
+		return error;
+	}
+
+	return 0;
+}
+module_init(whiskers_init);
+
+static void __exit whiskers_exit(void)
+{
+	hid_unregister_driver(&whiskers_hid_driver);
+	platform_driver_unregister(&whiskers_ec_driver);
+}
+module_exit(whiskers_exit);
+
+MODULE_LICENSE("GPL");
-- 
2.19.0.605.g01d371f741-goog