[PATCH] HID: hid-stadiaff: add support for Stadia force feedback

[Fabio Baltieri]

Add a hid-stadiaff module to support rumble based force feedback on the
Google Stadia controller. This works using the HID output endpoint
exposed on both the USB and BLE interface.

Signed-off-by: Fabio Baltieri <fabiobaltieri@xxxxxxxxxxxx>
---

Hi, this adds rumble support to the stadia controller using the input
interface. Up to now this has only been implemented at application level
using hidraw:

https://source.chromium.org/chromium/chromium/src/+/main:device/gamepad/hid_haptic_gamepad.cc

Tested with fftest, works both over USB and BLE.

 drivers/hid/Kconfig        |   7 ++
 drivers/hid/Makefile       |   1 +
 drivers/hid/hid-ids.h      |   1 +
 drivers/hid/hid-stadiaff.c | 132 +++++++++++++++++++++++++++++++++++++
 4 files changed, 141 insertions(+)
 create mode 100644 drivers/hid/hid-stadiaff.c

diff --git a/drivers/hid/Kconfig b/drivers/hid/Kconfig
index 82f64fb31fda..934f73e9b800 100644
--- a/drivers/hid/Kconfig
+++ b/drivers/hid/Kconfig
@@ -1031,6 +1031,13 @@ config HID_SPEEDLINK
 	help
 	Support for Speedlink Vicious and Divine Cezanne mouse.
 
+config HID_STADIA_FF
+	tristate "Google Stadia force feedback"
+	select INPUT_FF_MEMLESS
+	help
+	Say Y here if you want to enable force feedback support for the Google
+	Stadia controller.
+
 config HID_STEAM
 	tristate "Steam Controller/Deck support"
 	select POWER_SUPPLY
diff --git a/drivers/hid/Makefile b/drivers/hid/Makefile
index 5d37cacbde33..1d900fa55890 100644
--- a/drivers/hid/Makefile
+++ b/drivers/hid/Makefile
@@ -120,6 +120,7 @@ obj-$(CONFIG_HID_SIGMAMICRO)	+= hid-sigmamicro.o
 obj-$(CONFIG_HID_SMARTJOYPLUS)	+= hid-sjoy.o
 obj-$(CONFIG_HID_SONY)		+= hid-sony.o
 obj-$(CONFIG_HID_SPEEDLINK)	+= hid-speedlink.o
+obj-$(CONFIG_HID_STADIA_FF)	+= hid-stadiaff.o
 obj-$(CONFIG_HID_STEAM)		+= hid-steam.o
 obj-$(CONFIG_HID_STEELSERIES)	+= hid-steelseries.o
 obj-$(CONFIG_HID_SUNPLUS)	+= hid-sunplus.o
diff --git a/drivers/hid/hid-ids.h b/drivers/hid/hid-ids.h
index 63545cd307e5..cffd4ac609a0 100644
--- a/drivers/hid/hid-ids.h
+++ b/drivers/hid/hid-ids.h
@@ -525,6 +525,7 @@
 #define USB_DEVICE_ID_GOOGLE_MOONBALL	0x5044
 #define USB_DEVICE_ID_GOOGLE_DON	0x5050
 #define USB_DEVICE_ID_GOOGLE_EEL	0x5057
+#define USB_DEVICE_ID_GOOGLE_STADIA	0x9400
 
 #define USB_VENDOR_ID_GOTOP		0x08f2
 #define USB_DEVICE_ID_SUPER_Q2		0x007f
diff --git a/drivers/hid/hid-stadiaff.c b/drivers/hid/hid-stadiaff.c
new file mode 100644
index 000000000000..f974b9e24d46
--- /dev/null
+++ b/drivers/hid/hid-stadiaff.c
@@ -0,0 +1,132 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Stadia controller rumble support.
+ *
+ * Copyright 2023 Google LLC
+ */
+
+#include <linux/hid.h>
+#include <linux/input.h>
+#include <linux/slab.h>
+#include <linux/module.h>
+
+#include "hid-ids.h"
+
+#define STADIA_FF_REPORT_ID 5
+
+struct stadiaff_device {
+	struct hid_device *hid;
+	struct hid_report *report;
+	struct work_struct work;
+};
+
+static void stadiaff_work(struct work_struct *work)
+{
+	struct stadiaff_device *stadiaff =
+		container_of(work, struct stadiaff_device, work);
+
+	hid_hw_request(stadiaff->hid, stadiaff->report, HID_REQ_SET_REPORT);
+}
+
+static int stadiaff_play(struct input_dev *dev, void *data,
+			 struct ff_effect *effect)
+{
+	struct hid_device *hid = input_get_drvdata(dev);
+	struct stadiaff_device *stadiaff = hid_get_drvdata(hid);
+	struct hid_field *rumble_field = stadiaff->report->field[0];
+
+	rumble_field->value[0] = effect->u.rumble.strong_magnitude;
+	rumble_field->value[1] = effect->u.rumble.weak_magnitude;
+
+	schedule_work(&stadiaff->work);
+
+	return 0;
+}
+
+static int stadiaff_init(struct hid_device *hid)
+{
+	struct stadiaff_device *stadiaff;
+	struct hid_report *report;
+	struct hid_input *hidinput;
+	struct input_dev *dev;
+	int error;
+
+	if (list_empty(&hid->inputs)) {
+		hid_err(hid, "no inputs found\n");
+		return -ENODEV;
+	}
+	hidinput = list_entry(hid->inputs.next, struct hid_input, list);
+	dev = hidinput->input;
+
+	report = hid_validate_values(hid, HID_OUTPUT_REPORT,
+				     STADIA_FF_REPORT_ID, 0, 2);
+	if (!report)
+		return -ENODEV;
+
+	stadiaff = devm_kzalloc(&hid->dev, sizeof(struct stadiaff_device),
+				GFP_KERNEL);
+	if (!stadiaff)
+		return -ENOMEM;
+
+	hid_set_drvdata(hid, stadiaff);
+
+	input_set_capability(dev, EV_FF, FF_RUMBLE);
+
+	error = input_ff_create_memless(dev, NULL, stadiaff_play);
+	if (error)
+		return error;
+
+	stadiaff->hid = hid;
+	stadiaff->report = report;
+	INIT_WORK(&stadiaff->work, stadiaff_work);
+
+	hid_info(hid, "Force Feedback for Google Stadia controller\n");
+
+	return 0;
+}
+
+static int stadia_probe(struct hid_device *hdev, const struct hid_device_id *id)
+{
+	int ret;
+
+	ret = hid_parse(hdev);
+	if (ret) {
+		hid_err(hdev, "parse failed\n");
+		return ret;
+	}
+
+	ret = hid_hw_start(hdev, HID_CONNECT_DEFAULT & ~HID_CONNECT_FF);
+	if (ret) {
+		hid_err(hdev, "hw start failed\n");
+		return ret;
+	}
+
+	stadiaff_init(hdev);
+
+	return 0;
+}
+
+static void stadia_remove(struct hid_device *hid)
+{
+	struct stadiaff_device *stadiaff = hid_get_drvdata(hid);
+
+	cancel_work_sync(&stadiaff->work);
+	hid_hw_stop(hid);
+}
+
+static const struct hid_device_id stadia_devices[] = {
+	{ HID_USB_DEVICE(USB_VENDOR_ID_GOOGLE, USB_DEVICE_ID_GOOGLE_STADIA) },
+	{ HID_BLUETOOTH_DEVICE(USB_VENDOR_ID_GOOGLE, USB_DEVICE_ID_GOOGLE_STADIA) },
+	{ }
+};
+MODULE_DEVICE_TABLE(hid, stadia_devices);
+
+static struct hid_driver stadia_driver = {
+	.name = "stadia",
+	.id_table = stadia_devices,
+	.probe = stadia_probe,
+	.remove = stadia_remove,
+};
+module_hid_driver(stadia_driver);
+
+MODULE_LICENSE("GPL");
-- 
2.40.0.348.gf938b09366-goog