drm/amd/display: Try RGB before YCbCr 4:4:4 in stream validationgrafted

amdgpu_dm_create_validate_stream_for_sink() walks encoding_order[] and
uses the first encoding that validates. YCbCr 4:4:4 is listed before
RGB, so an HDMI sink that advertises 4:4:4 gets YCbCr 4:4:4 whenever the
"color format" property is left at AUTO, even though RGB fits the same
link.

That contradicts the documented AUTO behaviour for HDMI in enum
drm_connector_color_format (RGB, falling back to YCbCr 4:2:0 only when
the bandwidth is not available or the mode is 4:2:0-only), which the
amdgpu implementation of the property also describes. It also leaves
the "Broadcast RGB" property without effect on such sinks, since the
quantization range it selects only applies to RGB output.

Try RGB first. The mask still holds every encoding the sink supports,
so a mode that cannot carry RGB falls back exactly as before.

For reference, v7.2 picked RGB here unless YCbCr 4:4:4 was forced
through debugfs, while earlier kernels picked YCbCr 4:4:4 for any HDMI
sink that advertised it.

Fixes: 0b0ff65d3ca1 ("drm/amd/display: Refactor stream validation")
Suggested-by: Adolfo Rodrigues <adolfotregosa@gmail.com>
Assisted-by: Claude Code:claude-fable-5-1
Signed-off-by: Adrian Betschart <adrian.betschart@cinemaone.ch>
Reviewed-by: Fangzhi Zuo <jerry.zuo@amd.com>
Tested-by: Adolfo Rodrigues <adolfotregosa@gmail.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 7de432bc753133764dc40d37f9388da56de251e7)

6 files changed, 969 insertions, 0 deletions

diff --git a/drivers/hid/surface-hid/Kconfig b/drivers/hid/surface-hid/Kconfig
new file mode 100644
index 000000000..d0cfd0d29
--- /dev/null
+++ b/drivers/hid/surface-hid/Kconfig
@@ -0,0 +1,40 @@
+# SPDX-License-Identifier: GPL-2.0+
+menu "Surface System Aggregator Module HID support"
+	depends on SURFACE_AGGREGATOR
+
+config SURFACE_HID
+	tristate "HID transport driver for Surface System Aggregator Module"
+	depends on SURFACE_AGGREGATOR_REGISTRY
+	select SURFACE_HID_CORE
+	help
+	  Driver to support integrated HID devices on newer Microsoft Surface
+	  models.
+
+	  This driver provides support for the HID transport protocol provided
+	  by the Surface Aggregator Module (i.e. the embedded controller) on
+	  7th-generation Microsoft Surface devices, i.e. Surface Book 3 and
+	  Surface Laptop 3. On those models, it is mainly used to connect the
+	  integrated touchpad and keyboard.
+
+	  Say M or Y here, if you want support for integrated HID devices, i.e.
+	  integrated touchpad and keyboard, on 7th generation Microsoft Surface
+	  models.
+
+config SURFACE_KBD
+	tristate "HID keyboard transport driver for Surface System Aggregator Module"
+	select SURFACE_HID_CORE
+	help
+	  Driver to support HID keyboards on Surface Laptop 1 and 2 devices.
+
+	  This driver provides support for the HID transport protocol provided
+	  by the Surface Aggregator Module (i.e. the embedded controller) on
+	  Microsoft Surface Laptops 1 and 2. It is used to connect the
+	  integrated keyboard on those devices.
+
+	  Say M or Y here, if you want support for the integrated keyboard on
+	  Microsoft Surface Laptops 1 and 2.
+
+endmenu
+
+config SURFACE_HID_CORE
+	tristate
diff --git a/drivers/hid/surface-hid/Makefile b/drivers/hid/surface-hid/Makefile
new file mode 100644
index 000000000..4ae11cf09
--- /dev/null
+++ b/drivers/hid/surface-hid/Makefile
@@ -0,0 +1,7 @@
+# SPDX-License-Identifier: GPL-2.0+
+#
+# Makefile - Surface System Aggregator Module (SSAM) HID transport driver.
+#
+obj-$(CONFIG_SURFACE_HID_CORE)	+= surface_hid_core.o
+obj-$(CONFIG_SURFACE_HID)	+= surface_hid.o
+obj-$(CONFIG_SURFACE_KBD)	+= surface_kbd.o
diff --git a/drivers/hid/surface-hid/surface_hid.c b/drivers/hid/surface-hid/surface_hid.c
new file mode 100644
index 000000000..eae47e0d9
--- /dev/null
+++ b/drivers/hid/surface-hid/surface_hid.c
@@ -0,0 +1,253 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Surface System Aggregator Module (SSAM) HID transport driver for the
+ * generic HID interface (HID/TC=0x15 subsystem). Provides support for
+ * integrated HID devices on Surface Laptop 3, Book 3, and later.
+ *
+ * Copyright (C) 2019-2021 Blaž Hrastnik <blaz@mxxn.io>,
+ *                         Maximilian Luz <luzmaximilian@gmail.com>
+ */
+
+#include <linux/unaligned.h>
+#include <linux/hid.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/types.h>
+
+#include <linux/surface_aggregator/controller.h>
+#include <linux/surface_aggregator/device.h>
+
+#include "surface_hid_core.h"
+
+
+/* -- SAM interface. -------------------------------------------------------- */
+
+struct surface_hid_buffer_slice {
+	__u8 entry;
+	__le32 offset;
+	__le32 length;
+	__u8 end;
+	__u8 data[];
+} __packed;
+
+static_assert(sizeof(struct surface_hid_buffer_slice) == 10);
+
+enum surface_hid_cid {
+	SURFACE_HID_CID_OUTPUT_REPORT      = 0x01,
+	SURFACE_HID_CID_GET_FEATURE_REPORT = 0x02,
+	SURFACE_HID_CID_SET_FEATURE_REPORT = 0x03,
+	SURFACE_HID_CID_GET_DESCRIPTOR     = 0x04,
+};
+
+static int ssam_hid_get_descriptor(struct surface_hid_device *shid, u8 entry, u8 *buf, size_t len)
+{
+	u8 buffer[sizeof(struct surface_hid_buffer_slice) + 0x76];
+	struct surface_hid_buffer_slice *slice;
+	struct ssam_request rqst;
+	struct ssam_response rsp;
+	u32 buffer_len, offset, length;
+	int status;
+
+	/*
+	 * Note: The 0x76 above has been chosen because that's what's used by
+	 * the Windows driver. Together with the header, this leads to a 128
+	 * byte payload in total.
+	 */
+
+	buffer_len = ARRAY_SIZE(buffer) - sizeof(struct surface_hid_buffer_slice);
+
+	rqst.target_category = shid->uid.category;
+	rqst.target_id = shid->uid.target;
+	rqst.command_id = SURFACE_HID_CID_GET_DESCRIPTOR;
+	rqst.instance_id = shid->uid.instance;
+	rqst.flags = SSAM_REQUEST_HAS_RESPONSE;
+	rqst.length = sizeof(struct surface_hid_buffer_slice);
+	rqst.payload = buffer;
+
+	rsp.capacity = ARRAY_SIZE(buffer);
+	rsp.pointer = buffer;
+
+	slice = (struct surface_hid_buffer_slice *)buffer;
+	slice->entry = entry;
+	slice->end = 0;
+
+	offset = 0;
+	length = buffer_len;
+
+	while (!slice->end && offset < len) {
+		put_unaligned_le32(offset, &slice->offset);
+		put_unaligned_le32(length, &slice->length);
+
+		rsp.length = 0;
+
+		status = ssam_retry(ssam_request_do_sync_onstack, shid->ctrl, &rqst, &rsp,
+				    sizeof(*slice));
+		if (status)
+			return status;
+
+		offset = get_unaligned_le32(&slice->offset);
+		length = get_unaligned_le32(&slice->length);
+
+		/* Don't mess stuff up in case we receive garbage. */
+		if (length > buffer_len || offset > len)
+			return -EPROTO;
+
+		if (offset + length > len)
+			length = len - offset;
+
+		memcpy(buf + offset, &slice->data[0], length);
+
+		offset += length;
+		length = buffer_len;
+	}
+
+	if (offset != len) {
+		dev_err(shid->dev, "unexpected descriptor length: got %u, expected %zu\n",
+			offset, len);
+		return -EPROTO;
+	}
+
+	return 0;
+}
+
+static int ssam_hid_set_raw_report(struct surface_hid_device *shid, u8 rprt_id, bool feature,
+				   u8 *buf, size_t len)
+{
+	struct ssam_request rqst;
+	u8 cid;
+
+	if (feature)
+		cid = SURFACE_HID_CID_SET_FEATURE_REPORT;
+	else
+		cid = SURFACE_HID_CID_OUTPUT_REPORT;
+
+	rqst.target_category = shid->uid.category;
+	rqst.target_id = shid->uid.target;
+	rqst.instance_id = shid->uid.instance;
+	rqst.command_id = cid;
+	rqst.flags = 0;
+	rqst.length = len;
+	rqst.payload = buf;
+
+	buf[0] = rprt_id;
+
+	return ssam_retry(ssam_request_do_sync, shid->ctrl, &rqst, NULL);
+}
+
+static int ssam_hid_get_raw_report(struct surface_hid_device *shid, u8 rprt_id, u8 *buf, size_t len)
+{
+	struct ssam_request rqst;
+	struct ssam_response rsp;
+
+	rqst.target_category = shid->uid.category;
+	rqst.target_id = shid->uid.target;
+	rqst.instance_id = shid->uid.instance;
+	rqst.command_id = SURFACE_HID_CID_GET_FEATURE_REPORT;
+	rqst.flags = SSAM_REQUEST_HAS_RESPONSE;
+	rqst.length = sizeof(rprt_id);
+	rqst.payload = &rprt_id;
+
+	rsp.capacity = len;
+	rsp.length = 0;
+	rsp.pointer = buf;
+
+	return ssam_retry(ssam_request_do_sync_onstack, shid->ctrl, &rqst, &rsp, sizeof(rprt_id));
+}
+
+static u32 ssam_hid_event_fn(struct ssam_event_notifier *nf, const struct ssam_event *event)
+{
+	struct surface_hid_device *shid = container_of(nf, struct surface_hid_device, notif);
+
+	if (event->command_id != 0x00)
+		return 0;
+
+	hid_input_report(shid->hid, HID_INPUT_REPORT, (u8 *)&event->data[0], event->length, 0);
+	return SSAM_NOTIF_HANDLED;
+}
+
+
+/* -- Transport driver. ----------------------------------------------------- */
+
+static int shid_output_report(struct surface_hid_device *shid, u8 rprt_id, u8 *buf, size_t len)
+{
+	int status;
+
+	status = ssam_hid_set_raw_report(shid, rprt_id, false, buf, len);
+	return status >= 0 ? len : status;
+}
+
+static int shid_get_feature_report(struct surface_hid_device *shid, u8 rprt_id, u8 *buf, size_t len)
+{
+	int status;
+
+	status = ssam_hid_get_raw_report(shid, rprt_id, buf, len);
+	return status >= 0 ? len : status;
+}
+
+static int shid_set_feature_report(struct surface_hid_device *shid, u8 rprt_id, u8 *buf, size_t len)
+{
+	int status;
+
+	status = ssam_hid_set_raw_report(shid, rprt_id, true, buf, len);
+	return status >= 0 ? len : status;
+}
+
+
+/* -- Driver setup. --------------------------------------------------------- */
+
+static int surface_hid_probe(struct ssam_device *sdev)
+{
+	struct surface_hid_device *shid;
+
+	shid = devm_kzalloc(&sdev->dev, sizeof(*shid), GFP_KERNEL);
+	if (!shid)
+		return -ENOMEM;
+
+	shid->dev = &sdev->dev;
+	shid->ctrl = sdev->ctrl;
+	shid->uid = sdev->uid;
+
+	shid->notif.base.priority = 1;
+	shid->notif.base.fn = ssam_hid_event_fn;
+	shid->notif.event.reg = SSAM_EVENT_REGISTRY_REG(sdev->uid.target);
+	shid->notif.event.id.target_category = sdev->uid.category;
+	shid->notif.event.id.instance = sdev->uid.instance;
+	shid->notif.event.mask = SSAM_EVENT_MASK_STRICT;
+	shid->notif.event.flags = 0;
+
+	shid->ops.get_descriptor = ssam_hid_get_descriptor;
+	shid->ops.output_report = shid_output_report;
+	shid->ops.get_feature_report = shid_get_feature_report;
+	shid->ops.set_feature_report = shid_set_feature_report;
+
+	ssam_device_set_drvdata(sdev, shid);
+	return surface_hid_device_add(shid);
+}
+
+static void surface_hid_remove(struct ssam_device *sdev)
+{
+	surface_hid_device_destroy(ssam_device_get_drvdata(sdev));
+}
+
+static const struct ssam_device_id surface_hid_match[] = {
+	{ SSAM_SDEV(HID, ANY, SSAM_SSH_IID_ANY, 0x00) },
+	{ },
+};
+MODULE_DEVICE_TABLE(ssam, surface_hid_match);
+
+static struct ssam_device_driver surface_hid_driver = {
+	.probe = surface_hid_probe,
+	.remove = surface_hid_remove,
+	.match_table = surface_hid_match,
+	.driver = {
+		.name = "surface_hid",
+		.pm = &surface_hid_pm_ops,
+		.probe_type = PROBE_PREFER_ASYNCHRONOUS,
+	},
+};
+module_ssam_device_driver(surface_hid_driver);
+
+MODULE_AUTHOR("Blaž Hrastnik <blaz@mxxn.io>");
+MODULE_AUTHOR("Maximilian Luz <luzmaximilian@gmail.com>");
+MODULE_DESCRIPTION("HID transport driver for Surface System Aggregator Module");
+MODULE_LICENSE("GPL");
diff --git a/drivers/hid/surface-hid/surface_hid_core.c b/drivers/hid/surface-hid/surface_hid_core.c
new file mode 100644
index 000000000..6690c24f2
--- /dev/null
+++ b/drivers/hid/surface-hid/surface_hid_core.c
@@ -0,0 +1,293 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Common/core components for the Surface System Aggregator Module (SSAM) HID
+ * transport driver. Provides support for integrated HID devices on Microsoft
+ * Surface models.
+ *
+ * Copyright (C) 2019-2021 Maximilian Luz <luzmaximilian@gmail.com>
+ */
+
+#include <linux/unaligned.h>
+#include <linux/hid.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/types.h>
+#include <linux/usb/ch9.h>
+
+#include <linux/surface_aggregator/controller.h>
+
+#include "surface_hid_core.h"
+
+
+/* -- Utility functions. ---------------------------------------------------- */
+
+static bool surface_hid_is_hot_removed(struct surface_hid_device *shid)
+{
+	/*
+	 * Non-ssam client devices, i.e. platform client devices, cannot be
+	 * hot-removed.
+	 */
+	if (!is_ssam_device(shid->dev))
+		return false;
+
+	return ssam_device_is_hot_removed(to_ssam_device(shid->dev));
+}
+
+
+/* -- Device descriptor access. --------------------------------------------- */
+
+static int surface_hid_load_hid_descriptor(struct surface_hid_device *shid)
+{
+	int status;
+
+	if (surface_hid_is_hot_removed(shid))
+		return -ENODEV;
+
+	status = shid->ops.get_descriptor(shid, SURFACE_HID_DESC_HID,
+			(u8 *)&shid->hid_desc, sizeof(shid->hid_desc));
+	if (status)
+		return status;
+
+	if (shid->hid_desc.desc_len != sizeof(shid->hid_desc)) {
+		dev_err(shid->dev, "unexpected HID descriptor length: got %u, expected %zu\n",
+			shid->hid_desc.desc_len, sizeof(shid->hid_desc));
+		return -EPROTO;
+	}
+
+	if (shid->hid_desc.desc_type != HID_DT_HID) {
+		dev_err(shid->dev, "unexpected HID descriptor type: got %#04x, expected %#04x\n",
+			shid->hid_desc.desc_type, HID_DT_HID);
+		return -EPROTO;
+	}
+
+	if (shid->hid_desc.num_descriptors != 1) {
+		dev_err(shid->dev, "unexpected number of descriptors: got %u, expected 1\n",
+			shid->hid_desc.num_descriptors);
+		return -EPROTO;
+	}
+
+	if (shid->hid_desc.report_desc_type != HID_DT_REPORT) {
+		dev_err(shid->dev, "unexpected report descriptor type: got %#04x, expected %#04x\n",
+			shid->hid_desc.report_desc_type, HID_DT_REPORT);
+		return -EPROTO;
+	}
+
+	return 0;
+}
+
+static int surface_hid_load_device_attributes(struct surface_hid_device *shid)
+{
+	int status;
+
+	if (surface_hid_is_hot_removed(shid))
+		return -ENODEV;
+
+	status = shid->ops.get_descriptor(shid, SURFACE_HID_DESC_ATTRS,
+			(u8 *)&shid->attrs, sizeof(shid->attrs));
+	if (status)
+		return status;
+
+	if (get_unaligned_le32(&shid->attrs.length) != sizeof(shid->attrs)) {
+		dev_err(shid->dev, "unexpected attribute length: got %u, expected %zu\n",
+			get_unaligned_le32(&shid->attrs.length), sizeof(shid->attrs));
+		return -EPROTO;
+	}
+
+	return 0;
+}
+
+
+/* -- Transport driver (common). -------------------------------------------- */
+
+static int surface_hid_start(struct hid_device *hid)
+{
+	struct surface_hid_device *shid = hid->driver_data;
+
+	return ssam_notifier_register(shid->ctrl, &shid->notif);
+}
+
+static void surface_hid_stop(struct hid_device *hid)
+{
+	struct surface_hid_device *shid = hid->driver_data;
+	bool hot_removed;
+
+	/*
+	 * Communication may fail for devices that have been hot-removed. This
+	 * also includes unregistration of HID events, so we need to check this
+	 * here. Only if the device has not been marked as hot-removed, we can
+	 * safely disable events.
+	 */
+	hot_removed = surface_hid_is_hot_removed(shid);
+
+	/* Note: This call will log errors for us, so ignore them here. */
+	__ssam_notifier_unregister(shid->ctrl, &shid->notif, !hot_removed);
+}
+
+static int surface_hid_open(struct hid_device *hid)
+{
+	return 0;
+}
+
+static void surface_hid_close(struct hid_device *hid)
+{
+}
+
+static int surface_hid_parse(struct hid_device *hid)
+{
+	struct surface_hid_device *shid = hid->driver_data;
+	size_t len = get_unaligned_le16(&shid->hid_desc.report_desc_len);
+	u8 *buf;
+	int status;
+
+	if (surface_hid_is_hot_removed(shid))
+		return -ENODEV;
+
+	buf = kzalloc(len, GFP_KERNEL);
+	if (!buf)
+		return -ENOMEM;
+
+	status = shid->ops.get_descriptor(shid, SURFACE_HID_DESC_REPORT, buf, len);
+	if (!status)
+		status = hid_parse_report(hid, buf, len);
+
+	kfree(buf);
+	return status;
+}
+
+static int surface_hid_raw_request(struct hid_device *hid, unsigned char reportnum, u8 *buf,
+				   size_t len, unsigned char rtype, int reqtype)
+{
+	struct surface_hid_device *shid = hid->driver_data;
+
+	if (surface_hid_is_hot_removed(shid))
+		return -ENODEV;
+
+	if (rtype == HID_OUTPUT_REPORT && reqtype == HID_REQ_SET_REPORT)
+		return shid->ops.output_report(shid, reportnum, buf, len);
+
+	else if (rtype == HID_FEATURE_REPORT && reqtype == HID_REQ_GET_REPORT)
+		return shid->ops.get_feature_report(shid, reportnum, buf, len);
+
+	else if (rtype == HID_FEATURE_REPORT && reqtype == HID_REQ_SET_REPORT)
+		return shid->ops.set_feature_report(shid, reportnum, buf, len);
+
+	return -EIO;
+}
+
+static const struct hid_ll_driver surface_hid_ll_driver = {
+	.start       = surface_hid_start,
+	.stop        = surface_hid_stop,
+	.open        = surface_hid_open,
+	.close       = surface_hid_close,
+	.parse       = surface_hid_parse,
+	.raw_request = surface_hid_raw_request,
+};
+
+
+/* -- Common device setup. -------------------------------------------------- */
+
+int surface_hid_device_add(struct surface_hid_device *shid)
+{
+	int status;
+
+	status = surface_hid_load_hid_descriptor(shid);
+	if (status)
+		return status;
+
+	status = surface_hid_load_device_attributes(shid);
+	if (status)
+		return status;
+
+	shid->hid = hid_allocate_device();
+	if (IS_ERR(shid->hid))
+		return PTR_ERR(shid->hid);
+
+	shid->hid->dev.parent = shid->dev;
+	shid->hid->bus = BUS_HOST;
+	shid->hid->vendor = get_unaligned_le16(&shid->attrs.vendor);
+	shid->hid->product = get_unaligned_le16(&shid->attrs.product);
+	shid->hid->version = get_unaligned_le16(&shid->hid_desc.hid_version);
+	shid->hid->country = shid->hid_desc.country_code;
+
+	snprintf(shid->hid->name, sizeof(shid->hid->name), "Microsoft Surface %04X:%04X",
+		 shid->hid->vendor, shid->hid->product);
+
+	strscpy(shid->hid->phys, dev_name(shid->dev), sizeof(shid->hid->phys));
+
+	shid->hid->driver_data = shid;
+	shid->hid->ll_driver = &surface_hid_ll_driver;
+
+	status = hid_add_device(shid->hid);
+	if (status)
+		hid_destroy_device(shid->hid);
+
+	return status;
+}
+EXPORT_SYMBOL_GPL(surface_hid_device_add);
+
+void surface_hid_device_destroy(struct surface_hid_device *shid)
+{
+	hid_destroy_device(shid->hid);
+}
+EXPORT_SYMBOL_GPL(surface_hid_device_destroy);
+
+
+/* -- PM ops. --------------------------------------------------------------- */
+
+#ifdef CONFIG_PM_SLEEP
+
+static int surface_hid_suspend(struct device *dev)
+{
+	struct surface_hid_device *d = dev_get_drvdata(dev);
+
+	return hid_driver_suspend(d->hid, PMSG_SUSPEND);
+}
+
+static int surface_hid_resume(struct device *dev)
+{
+	struct surface_hid_device *d = dev_get_drvdata(dev);
+
+	return hid_driver_resume(d->hid);
+}
+
+static int surface_hid_freeze(struct device *dev)
+{
+	struct surface_hid_device *d = dev_get_drvdata(dev);
+
+	return hid_driver_suspend(d->hid, PMSG_FREEZE);
+}
+
+static int surface_hid_poweroff(struct device *dev)
+{
+	struct surface_hid_device *d = dev_get_drvdata(dev);
+
+	return hid_driver_suspend(d->hid, PMSG_HIBERNATE);
+}
+
+static int surface_hid_restore(struct device *dev)
+{
+	struct surface_hid_device *d = dev_get_drvdata(dev);
+
+	return hid_driver_reset_resume(d->hid);
+}
+
+const struct dev_pm_ops surface_hid_pm_ops = {
+	.freeze   = surface_hid_freeze,
+	.thaw     = surface_hid_resume,
+	.suspend  = surface_hid_suspend,
+	.resume   = surface_hid_resume,
+	.poweroff = surface_hid_poweroff,
+	.restore  = surface_hid_restore,
+};
+EXPORT_SYMBOL_GPL(surface_hid_pm_ops);
+
+#else /* CONFIG_PM_SLEEP */
+
+const struct dev_pm_ops surface_hid_pm_ops = { };
+EXPORT_SYMBOL_GPL(surface_hid_pm_ops);
+
+#endif /* CONFIG_PM_SLEEP */
+
+MODULE_AUTHOR("Maximilian Luz <luzmaximilian@gmail.com>");
+MODULE_DESCRIPTION("HID transport driver core for Surface System Aggregator Module");
+MODULE_LICENSE("GPL");
diff --git a/drivers/hid/surface-hid/surface_hid_core.h b/drivers/hid/surface-hid/surface_hid_core.h
new file mode 100644
index 000000000..4b1a7b57e
--- /dev/null
+++ b/drivers/hid/surface-hid/surface_hid_core.h
@@ -0,0 +1,77 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * Common/core components for the Surface System Aggregator Module (SSAM) HID
+ * transport driver. Provides support for integrated HID devices on Microsoft
+ * Surface models.
+ *
+ * Copyright (C) 2019-2021 Maximilian Luz <luzmaximilian@gmail.com>
+ */
+
+#ifndef SURFACE_HID_CORE_H
+#define SURFACE_HID_CORE_H
+
+#include <linux/hid.h>
+#include <linux/pm.h>
+#include <linux/types.h>
+
+#include <linux/surface_aggregator/controller.h>
+#include <linux/surface_aggregator/device.h>
+
+enum surface_hid_descriptor_entry {
+	SURFACE_HID_DESC_HID    = 0,
+	SURFACE_HID_DESC_REPORT = 1,
+	SURFACE_HID_DESC_ATTRS  = 2,
+};
+
+struct surface_hid_descriptor {
+	__u8 desc_len;			/* = 9 */
+	__u8 desc_type;			/* = HID_DT_HID */
+	__le16 hid_version;
+	__u8 country_code;
+	__u8 num_descriptors;		/* = 1 */
+
+	__u8 report_desc_type;		/* = HID_DT_REPORT */
+	__le16 report_desc_len;
+} __packed;
+
+static_assert(sizeof(struct surface_hid_descriptor) == 9);
+
+struct surface_hid_attributes {
+	__le32 length;
+	__le16 vendor;
+	__le16 product;
+	__le16 version;
+	__u8 _unknown[22];
+} __packed;
+
+static_assert(sizeof(struct surface_hid_attributes) == 32);
+
+struct surface_hid_device;
+
+struct surface_hid_device_ops {
+	int (*get_descriptor)(struct surface_hid_device *shid, u8 entry, u8 *buf, size_t len);
+	int (*output_report)(struct surface_hid_device *shid, u8 rprt_id, u8 *buf, size_t len);
+	int (*get_feature_report)(struct surface_hid_device *shid, u8 rprt_id, u8 *buf, size_t len);
+	int (*set_feature_report)(struct surface_hid_device *shid, u8 rprt_id, u8 *buf, size_t len);
+};
+
+struct surface_hid_device {
+	struct device *dev;
+	struct ssam_controller *ctrl;
+	struct ssam_device_uid uid;
+
+	struct surface_hid_descriptor hid_desc;
+	struct surface_hid_attributes attrs;
+
+	struct ssam_event_notifier notif;
+	struct hid_device *hid;
+
+	struct surface_hid_device_ops ops;
+};
+
+int surface_hid_device_add(struct surface_hid_device *shid);
+void surface_hid_device_destroy(struct surface_hid_device *shid);
+
+extern const struct dev_pm_ops surface_hid_pm_ops;
+
+#endif /* SURFACE_HID_CORE_H */
diff --git a/drivers/hid/surface-hid/surface_kbd.c b/drivers/hid/surface-hid/surface_kbd.c
new file mode 100644
index 000000000..0be01b5e7
--- /dev/null
+++ b/drivers/hid/surface-hid/surface_kbd.c
@@ -0,0 +1,299 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Surface System Aggregator Module (SSAM) HID transport driver for the legacy
+ * keyboard interface (KBD/TC=0x08 subsystem). Provides support for the
+ * integrated HID keyboard on Surface Laptops 1 and 2.
+ *
+ * Copyright (C) 2019-2021 Maximilian Luz <luzmaximilian@gmail.com>
+ */
+
+#include <linux/unaligned.h>
+#include <linux/hid.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/types.h>
+
+#include <linux/surface_aggregator/controller.h>
+
+#include "surface_hid_core.h"
+
+
+/* -- SAM interface (KBD). -------------------------------------------------- */
+
+#define KBD_FEATURE_REPORT_SIZE			7  /* 6 + report ID */
+
+enum surface_kbd_cid {
+	SURFACE_KBD_CID_GET_DESCRIPTOR		= 0x00,
+	SURFACE_KBD_CID_SET_CAPSLOCK_LED	= 0x01,
+	SURFACE_KBD_CID_EVT_INPUT_GENERIC	= 0x03,
+	SURFACE_KBD_CID_EVT_INPUT_HOTKEYS	= 0x04,
+	SURFACE_KBD_CID_GET_FEATURE_REPORT	= 0x0b,
+};
+
+static int ssam_kbd_get_descriptor(struct surface_hid_device *shid, u8 entry, u8 *buf, size_t len)
+{
+	struct ssam_request rqst;
+	struct ssam_response rsp;
+	int status;
+
+	rqst.target_category = shid->uid.category;
+	rqst.target_id = shid->uid.target;
+	rqst.command_id = SURFACE_KBD_CID_GET_DESCRIPTOR;
+	rqst.instance_id = shid->uid.instance;
+	rqst.flags = SSAM_REQUEST_HAS_RESPONSE;
+	rqst.length = sizeof(entry);
+	rqst.payload = &entry;
+
+	rsp.capacity = len;
+	rsp.length = 0;
+	rsp.pointer = buf;
+
+	status = ssam_retry(ssam_request_do_sync_onstack, shid->ctrl, &rqst, &rsp, sizeof(entry));
+	if (status)
+		return status;
+
+	if (rsp.length != len) {
+		dev_err(shid->dev, "invalid descriptor length: got %zu, expected, %zu\n",
+			rsp.length, len);
+		return -EPROTO;
+	}
+
+	return 0;
+}
+
+static int ssam_kbd_set_caps_led(struct surface_hid_device *shid, bool value)
+{
+	struct ssam_request rqst;
+	u8 value_u8 = value;
+
+	rqst.target_category = shid->uid.category;
+	rqst.target_id = shid->uid.target;
+	rqst.command_id = SURFACE_KBD_CID_SET_CAPSLOCK_LED;
+	rqst.instance_id = shid->uid.instance;
+	rqst.flags = 0;
+	rqst.length = sizeof(value_u8);
+	rqst.payload = &value_u8;
+
+	return ssam_retry(ssam_request_do_sync_onstack, shid->ctrl, &rqst, NULL, sizeof(value_u8));
+}
+
+static int ssam_kbd_get_feature_report(struct surface_hid_device *shid, u8 *buf, size_t len)
+{
+	struct ssam_request rqst;
+	struct ssam_response rsp;
+	u8 payload = 0;
+	int status;
+
+	rqst.target_category = shid->uid.category;
+	rqst.target_id = shid->uid.target;
+	rqst.command_id = SURFACE_KBD_CID_GET_FEATURE_REPORT;
+	rqst.instance_id = shid->uid.instance;
+	rqst.flags = SSAM_REQUEST_HAS_RESPONSE;
+	rqst.length = sizeof(payload);
+	rqst.payload = &payload;
+
+	rsp.capacity = len;
+	rsp.length = 0;
+	rsp.pointer = buf;
+
+	status = ssam_retry(ssam_request_do_sync_onstack, shid->ctrl, &rqst, &rsp, sizeof(payload));
+	if (status)
+		return status;
+
+	if (rsp.length != len) {
+		dev_err(shid->dev, "invalid feature report length: got %zu, expected, %zu\n",
+			rsp.length, len);
+		return -EPROTO;
+	}
+
+	return 0;
+}
+
+static bool ssam_kbd_is_input_event(const struct ssam_event *event)
+{
+	if (event->command_id == SURFACE_KBD_CID_EVT_INPUT_GENERIC)
+		return true;
+
+	if (event->command_id == SURFACE_KBD_CID_EVT_INPUT_HOTKEYS)
+		return true;
+
+	return false;
+}
+
+static u32 ssam_kbd_event_fn(struct ssam_event_notifier *nf, const struct ssam_event *event)
+{
+	struct surface_hid_device *shid = container_of(nf, struct surface_hid_device, notif);
+
+	/*
+	 * Check against device UID manually, as registry and device target
+	 * category doesn't line up.
+	 */
+
+	if (shid->uid.category != event->target_category)
+		return 0;
+
+	if (shid->uid.target != event->target_id)
+		return 0;
+
+	if (shid->uid.instance != event->instance_id)
+		return 0;
+
+	if (!ssam_kbd_is_input_event(event))
+		return 0;
+
+	hid_input_report(shid->hid, HID_INPUT_REPORT, (u8 *)&event->data[0], event->length, 0);
+	return SSAM_NOTIF_HANDLED;
+}
+
+
+/* -- Transport driver (KBD). ----------------------------------------------- */
+
+static int skbd_get_caps_led_value(struct hid_device *hid, u8 rprt_id, u8 *buf, size_t len)
+{
+	struct hid_field *field;
+	unsigned int offset, size;
+	int i;
+
+	/* Get LED field. */
+	field = hidinput_get_led_field(hid);
+	if (!field)
+		return -ENOENT;
+
+	/* Check if we got the correct report. */
+	if (len != hid_report_len(field->report))
+		return -ENOENT;
+
+	if (rprt_id != field->report->id)
+		return -ENOENT;
+
+	/* Get caps lock LED index. */
+	for (i = 0; i < field->report_count; i++)
+		if ((field->usage[i].hid & 0xffff) == 0x02)
+			break;
+
+	if (i == field->report_count)
+		return -ENOENT;
+
+	/* Extract value. */
+	size = field->report_size;
+	offset = field->report_offset + i * size;
+	return !!hid_field_extract(hid, buf + 1, size, offset);
+}
+
+static int skbd_output_report(struct surface_hid_device *shid, u8 rprt_id, u8 *buf, size_t len)
+{
+	int caps_led;
+	int status;
+
+	caps_led = skbd_get_caps_led_value(shid->hid, rprt_id, buf, len);
+	if (caps_led < 0)
+		return -EIO;  /* Only caps LED output reports are supported. */
+
+	status = ssam_kbd_set_caps_led(shid, caps_led);
+	if (status < 0)
+		return status;
+
+	return len;
+}
+
+static int skbd_get_feature_report(struct surface_hid_device *shid, u8 rprt_id, u8 *buf, size_t len)
+{
+	u8 report[KBD_FEATURE_REPORT_SIZE];
+	int status;
+
+	/*
+	 * The keyboard only has a single hard-coded read-only feature report
+	 * of size KBD_FEATURE_REPORT_SIZE. Try to load it and compare its
+	 * report ID against the requested one.
+	 */
+
+	if (len < ARRAY_SIZE(report))
+		return -ENOSPC;
+
+	status = ssam_kbd_get_feature_report(shid, report, ARRAY_SIZE(report));
+	if (status < 0)
+		return status;
+
+	if (rprt_id != report[0])
+		return -ENOENT;
+
+	memcpy(buf, report, ARRAY_SIZE(report));
+	return len;
+}
+
+static int skbd_set_feature_report(struct surface_hid_device *shid, u8 rprt_id, u8 *buf, size_t len)
+{
+	/* Not supported. See skbd_get_feature_report() for details. */
+	return -EIO;
+}
+
+
+/* -- Driver setup. --------------------------------------------------------- */
+
+static int surface_kbd_probe(struct platform_device *pdev)
+{
+	struct ssam_controller *ctrl;
+	struct surface_hid_device *shid;
+
+	/* Add device link to EC. */
+	ctrl = ssam_client_bind(&pdev->dev);
+	if (IS_ERR(ctrl))
+		return PTR_ERR(ctrl) == -ENODEV ? -EPROBE_DEFER : PTR_ERR(ctrl);
+
+	shid = devm_kzalloc(&pdev->dev, sizeof(*shid), GFP_KERNEL);
+	if (!shid)
+		return -ENOMEM;
+
+	shid->dev = &pdev->dev;
+	shid->ctrl = ctrl;
+
+	shid->uid.domain = SSAM_DOMAIN_SERIALHUB;
+	shid->uid.category = SSAM_SSH_TC_KBD;
+	shid->uid.target = SSAM_SSH_TID_KIP;
+	shid->uid.instance = 0;
+	shid->uid.function = 0;
+
+	shid->notif.base.priority = 1;
+	shid->notif.base.fn = ssam_kbd_event_fn;
+	shid->notif.event.reg = SSAM_EVENT_REGISTRY_SAM;
+	shid->notif.event.id.target_category = shid->uid.category;
+	shid->notif.event.id.instance = shid->uid.instance;
+	shid->notif.event.mask = SSAM_EVENT_MASK_NONE;
+	shid->notif.event.flags = 0;
+
+	shid->ops.get_descriptor = ssam_kbd_get_descriptor;
+	shid->ops.output_report = skbd_output_report;
+	shid->ops.get_feature_report = skbd_get_feature_report;
+	shid->ops.set_feature_report = skbd_set_feature_report;
+
+	platform_set_drvdata(pdev, shid);
+	return surface_hid_device_add(shid);
+}
+
+static void surface_kbd_remove(struct platform_device *pdev)
+{
+	surface_hid_device_destroy(platform_get_drvdata(pdev));
+}
+
+static const struct acpi_device_id surface_kbd_match[] = {
+	{ "MSHW0096" },
+	{ },
+};
+MODULE_DEVICE_TABLE(acpi, surface_kbd_match);
+
+static struct platform_driver surface_kbd_driver = {
+	.probe = surface_kbd_probe,
+	.remove = surface_kbd_remove,
+	.driver = {
+		.name = "surface_keyboard",
+		.acpi_match_table = surface_kbd_match,
+		.pm = &surface_hid_pm_ops,
+		.probe_type = PROBE_PREFER_ASYNCHRONOUS,
+	},
+};
+module_platform_driver(surface_kbd_driver);
+
+MODULE_AUTHOR("Maximilian Luz <luzmaximilian@gmail.com>");
+MODULE_DESCRIPTION("HID legacy transport driver for Surface System Aggregator Module");
+MODULE_LICENSE("GPL");