[PATCH v2 5/5] Input: misc: Add AMD SFH tablet-mode switch driver

[Basavaraj Natikar <Basavaraj.Natikar@amd.com>]

Report whether an AMD convertible is in laptop or tablet mode using the
operating-mode sensor provided by the Sensor Fusion Hub, and expose it
to userspace as SW_TABLET_MODE, so userspace can react to the device
being folded into tablet posture.

Cc: Helge Bahmann <hcb@chaoticmind.net>
Signed-off-by: Basavaraj Natikar <Basavaraj.Natikar@amd.com>
---
 MAINTAINERS                             |  1 +
 drivers/input/misc/Kconfig              | 15 +++++
 drivers/input/misc/Makefile             |  1 +
 drivers/input/misc/amd_sfh_tabletmode.c | 81 +++++++++++++++++++++++++
 4 files changed, 98 insertions(+)
 create mode 100644 drivers/input/misc/amd_sfh_tabletmode.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 5114e6db7307..30b429eb9286 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -1301,6 +1301,7 @@ L:	linux-input@vger.kernel.org
 S:	Maintained
 F:	Documentation/hid/amd-sfh*
 F:	drivers/hid/amd-sfh-hid/
+F:	drivers/input/misc/amd_sfh_tabletmode.c
 
 AMD SPI DRIVER
 M:	Raju Rangoju <Raju.Rangoju@amd.com>
diff --git a/drivers/input/misc/Kconfig b/drivers/input/misc/Kconfig
index 1f6c57dba030..5b76be31f687 100644
--- a/drivers/input/misc/Kconfig
+++ b/drivers/input/misc/Kconfig
@@ -899,6 +899,21 @@ config INPUT_SOC_BUTTON_ARRAY
 	  To compile this driver as a module, choose M here: the
 	  module will be called soc_button_array.
 
+config INPUT_AMD_SFH_TABLETMODE
+	tristate "AMD SFH tablet-mode switch"
+	depends on AMD_SFH_HID
+	select AUXILIARY_BUS
+	help
+	  Expose SW_TABLET_MODE for AMD convertible laptops whose
+	  operation-mode sensor is provided by the AMD Sensor Fusion Hub.
+
+	  Userspace components such as systemd-logind and modern desktop
+	  environments react to SW_TABLET_MODE when the device is folded
+	  into tablet posture.
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called amd_sfh_tabletmode.
+
 config INPUT_DRV260X_HAPTICS
 	tristate "TI DRV260X haptics support"
 	depends on INPUT && I2C
diff --git a/drivers/input/misc/Makefile b/drivers/input/misc/Makefile
index 2281d6803fce..72aa0658ebb3 100644
--- a/drivers/input/misc/Makefile
+++ b/drivers/input/misc/Makefile
@@ -81,6 +81,7 @@ obj-$(CONFIG_INPUT_RK805_PWRKEY)	+= rk805-pwrkey.o
 obj-$(CONFIG_INPUT_SC27XX_VIBRA)	+= sc27xx-vibra.o
 obj-$(CONFIG_INPUT_SGI_BTNS)		+= sgi_btns.o
 obj-$(CONFIG_INPUT_SOC_BUTTON_ARRAY)	+= soc_button_array.o
+obj-$(CONFIG_INPUT_AMD_SFH_TABLETMODE)	+= amd_sfh_tabletmode.o
 obj-$(CONFIG_INPUT_SPARCSPKR)		+= sparcspkr.o
 obj-$(CONFIG_INPUT_STPMIC1_ONKEY)  	+= stpmic1_onkey.o
 obj-$(CONFIG_INPUT_TPS65218_PWRBUTTON)	+= tps65218-pwrbutton.o
diff --git a/drivers/input/misc/amd_sfh_tabletmode.c b/drivers/input/misc/amd_sfh_tabletmode.c
new file mode 100644
index 000000000000..3931a1c6eb74
--- /dev/null
+++ b/drivers/input/misc/amd_sfh_tabletmode.c
@@ -0,0 +1,81 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * AMD SFH tablet-mode switch driver
+ *
+ * Copyright (c) 2026, Advanced Micro Devices, Inc.
+ * All Rights Reserved.
+ *
+ * Author: Basavaraj Natikar <Basavaraj.Natikar@amd.com>
+ */
+
+#include <linux/amd-pmf-io.h>
+#include <linux/auxiliary_bus.h>
+#include <linux/input.h>
+#include <linux/module.h>
+#include <linux/pci_ids.h>
+
+#define POLL_INTERVAL_MS	200
+
+static void sfh_tm_poll(struct input_dev *input)
+{
+	struct amd_sfh_info info = {};
+
+	if (amd_get_sfh_info(&info, MT_OP_MODE))
+		return;
+
+	input_report_switch(input, SW_TABLET_MODE,
+			    info.op_mode == SFH_MODE_TABLET);
+	input_sync(input);
+}
+
+static int sfh_tm_probe(struct auxiliary_device *auxdev,
+			const struct auxiliary_device_id *id)
+{
+	struct device *dev = &auxdev->dev;
+	struct amd_sfh_info info = {};
+	struct input_dev *input;
+	int error;
+
+	error = amd_get_sfh_info(&info, MT_OP_MODE);
+	if (error)
+		return error == -EINVAL ? -ENODEV : error;
+
+	input = devm_input_allocate_device(dev);
+	if (!input)
+		return -ENOMEM;
+
+	input->name		= "AMD SFH tablet mode switch";
+	input->phys		= "amd-sfh/tabletmode";
+	input->id.bustype	= BUS_HOST;
+	input->id.vendor	= PCI_VENDOR_ID_AMD;
+	input_set_capability(input, EV_SW, SW_TABLET_MODE);
+
+	error = input_setup_polling(input, sfh_tm_poll);
+	if (error)
+		return error;
+	input_set_poll_interval(input, POLL_INTERVAL_MS);
+
+	sfh_tm_poll(input);
+
+	error = input_register_device(input);
+	if (error)
+		return error;
+
+	return 0;
+}
+
+static const struct auxiliary_device_id sfh_tm_id_table[] = {
+	{ .name = "amd_sfh.tabletmode" },
+	{}
+};
+MODULE_DEVICE_TABLE(auxiliary, sfh_tm_id_table);
+
+static struct auxiliary_driver sfh_tm_driver = {
+	.name		= "tabletmode",
+	.id_table	= sfh_tm_id_table,
+	.probe		= sfh_tm_probe,
+};
+module_auxiliary_driver(sfh_tm_driver);
+
+MODULE_DESCRIPTION("AMD SFH tablet mode switch");
+MODULE_LICENSE("GPL");
-- 
2.34.1