Merge tag 'trace-v7.3-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-tracegrafted

Pull tracing fixes from Steven Rostedt:

 - Don't destroy user event fields when removal fails

   User event fields are destroyed before the event is removed from
   visibility. But that can fail leaving the still visible event with no
   fields. Move the destroying of the fields to after the event is
   successfully removed from visibility.

 - Initialize function graph state is fork before calling
   copy_exec_state()

   For non-CLONE_VM forks, copy_exec_state() allocates a new
   task_exec_state. If that allocation fails, ftrace_graph_exit_task()
   will free the tasks ret_stack pointer. Since that pointer is still
   using the parent's ret_stack, it mistakenly frees the parent's
   pointer too.

   Call ftrace_graph_init() on the task first which will NULL out the
   new tasks's ret_stack and if the copy fails, it will not free
   anything.

 - Remove FGRAPH_MAX_INDEX

   The macro FGRAPH_MAX_INDEX was added but never used. Remove it.

 - Save ent_size in function graph printing of nested functions

   The function graph tracer needs to look at the next event to see if
   the next event is the return of the current function entry. If it is,
   it prints a single line:

	ktime_get();

   Otherwise it prints it like a nested function:

	tick_nohz_irq_exit() {
	    ktime_get();
	    kcpustat_irq_exit();
	}

   In order to look at the next event, it must save the current event so
   that it has the information to print from it. It saves the event in
   the iterator descriptor called "ent". What it doesn't save is the
   ent_size of the event which is now used to know if the function graph
   arguments are to be printed. The peek doesn't save the size so the
   size used happens to be that of the size of the last event that was
   seen.

   Save the entry event size in the iterator descriptor so that the
   correct size is used.

 - Fix several errors with freeing data in the histogram code

   The histogram code had a lot of leaked or or incorrect accounting
   when failures happen. Correct them.

 - Fix histogram regression of .percent and .graph modifiers

   Up until 6.3 histogram values could have "percent" or "graph"
   modifiers that changed how they were printed. But a change that added
   restricting histograms values from being strings, stack traces and
   other modifiers inadvertently prevented them from using the percent
   and graph modifiers, which were legal use cases for values.

   Put back the percent and graph modifiers.

 - Fix various typos in the comments

 - Set the trace_clock before initializing a histogram with clock
   argument

   The histogram API allows the user to specific which trace clock to
   use via a "clock=" string. The histogram is set up first before the
   clock is checked. If the passed in clock is not valid, it exits
   without fully fixing up the histogram leaving it on the list and a
   use-after-free can trigger.

   Update the clock argument first and if it fails then exit gracefully
   before the histogram trigger is placed on any lists.

 - Restore :mod: trailer after parsing in ftrace_set_clr_event

   The function ftrace_set_clr_event() modifies the parse string and
   needs to put it back to what was passed in. It searches for ":mod:"
   via a strsep() but fails to put back the first ':' in the string.

   Add back the ':' in the passed in string.

 - Take trace_array reference when opening a tracer options file

   The options files are dynamically created and some tracers add their
   own options. When a tracer adds their own list of options, the
   trace_array holding them has an array to hold the list of options for
   each tracer. This array increases in size via a krealloc(), and the
   new entry gets a newly allocated array to hold the options of the new
   tracer being added.

   The element in each entry of the tracer's option array holds a
   pointer back to the trace_array, a pointer to the tracer it is
   associated to, a pointer to the flags of the option.

   The issue is that these arrays are freed when the trace_array is
   freed when its instance it represents is removed from the instances
   directory. There's a race that an open of one of these options files
   can happen when the instance is being removed.

   Add a new helper function to be called by the open function of the
   options file to iterate all existing trace_arrays under a lock and
   find the one that has the given option element in one of it's tracer
   arrays. If found, then update the associated trace_array's reference
   counter to keep it from being freed. If not found, have the open call
   return -ENODEV.

 - Disable interrupts when acquiring the lock in rb_wake_up_waiters()

   The function rb_wake_up_waiters() assumes it will be called in
   interrupt context and does not disable irqs when taking
   cpu_buffer->reader_lock, which can be called in hard interrupt
   context. The issue is in PREEMPT_RT, this function is called in
   thread context leaving this lock open to a deadlock.

   Take the lock with interrupts disabled.

 - Use rcu_assign_pointer() for tmp_ops filter hash

   The tmp_ops used in update_ftrace_direct_mod() assigns its
   filter_hash field directly, but that field is annotated as __rcu and
   sparse complains. Assign it with rcu_assign_pointer()

 - Fix use-after-free in enable_trigger_private_data_free()

   The trace_event_call is accessed through the event_trigger_data's
   trace_event_file pointer to put the trace_event_call on freeing. The
   issue is that the trace_event_file data may have been freed already
   causing a use-after-free. Add a field to the event_trigger_data that
   points directly to the trace_event_call so that it can decrement its
   reference directly without needing to go through the
   trace_event_file.

 - Fix accounting of buffer data remote headers

   trace_buffer_desc_size() and trace_remote_alloc_buffer() undercount
   the number of pages is needed for the asked for size as it doesn't
   take into account the meta data on each page. Add a helper function
   to do the calculation properly and use that in these functions.

 - Catch nr_page_va overflow in ring_buffer_desc sizing

   The number of pages per remote ring buffer is capped by
   ring_buffer_desc::nr_page_va (32 bits). A buffer_size large enough to
   overflow that field would silently allocate a descriptor smaller than
   what was asked for.

 - Do not resize the subbuf order if any per_cpu buffer is disabled

   The mmapping of ring buffers disables resizing the subbuffers, but it
   is done per-cpu whereas the subbuf size change is done for all the
   per_cpu buffers under the buffer->mutex. It could change the size of
   some while the mapping is happening on others. Have the resize of the
   subbuf order check all the per_cpu buffers under the lock to see if
   any of them is disabled before starting and causing an inconsistency
   between buffers that are being mapped.

* tag 'trace-v7.3-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: (25 commits)
  ring-buffer: Check resize_disabled before publishing the new subbuf order
  tracing/remotes: Catch nr_page_va overflow in ring_buffer_desc sizing
  tracing/remotes: Account for ring buffer page header in size calculation
  tracing: Don't dereference trace_event_file in deferred trigger free
  ftrace: Use rcu_assign_pointer() for tmp_ops filter hash
  ring-buffer: Acquire the lock with irqsave in rb_wake_up_waiters()
  tracing: Take trace_array reference when opening a tracer options file
  tracing: Fix ring_buffer_read_page_size() kernel-doc
  tracing: Restore :mod: trailer after parsing in ftrace_set_clr_event()
  tracing: Fix memory corruption from a "STACKTRACE" histogram key
  tracing: Fix memory corruption from the histogram stacktrace modifier
  tracing: Undo the registration when enabling the histogram trigger fails
  tracing: Take the reference before publishing the named histogram trigger
  tracing: Set the trace clock before registering the histogram trigger
  tracing: Fix typo "preceeded" in comment
  tracing: Fix typo "availabe" in comment
  tracing: Let histogram values keep the percent and graph modifiers
  tracing: Keep the entry count when the histogram stats allocation fails
  tracing: Free histogram the field rejected for a bad modifier
  tracing: Free histogram the var ref when its initialization fails
  ...

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");