lede/target/linux/silicon/patches-5.19/0130-hid-Add-Apple-DockChannel-HID-transport-driver.patch

From 55af457be82d0853857bab148c649a328aa58ffa Mon Sep 17 00:00:00 2001
From: Hector Martin <marcan@marcan.st>
Date: Fri, 8 Jul 2022 02:11:21 +0900
Subject: [PATCH 130/171] hid: Add Apple DockChannel HID transport driver

Apple M2 devices have an MTP coprocessor embedded in the SoC that
handles HID for the integrated touchpad/keyboard, and communicates
over the DockChannel interface. This driver implements this new
interface.

Signed-off-by: Hector Martin <marcan@marcan.st>
---
 drivers/hid/Kconfig                           |    2 +
 drivers/hid/Makefile                          |    2 +
 drivers/hid/dockchannel-hid/Kconfig           |   14 +
 drivers/hid/dockchannel-hid/Makefile          |    6 +
 drivers/hid/dockchannel-hid/dockchannel-hid.c | 1058 +++++++++++++++++
 5 files changed, 1082 insertions(+)
 create mode 100644 drivers/hid/dockchannel-hid/Kconfig
 create mode 100644 drivers/hid/dockchannel-hid/Makefile
 create mode 100644 drivers/hid/dockchannel-hid/dockchannel-hid.c

diff --git a/drivers/hid/Kconfig b/drivers/hid/Kconfig
index 1dd6697e7c59..bd47caba1413 100644
--- a/drivers/hid/Kconfig
+++ b/drivers/hid/Kconfig
@@ -1324,4 +1324,6 @@ source "drivers/hid/surface-hid/Kconfig"
 
 source "drivers/hid/spi-hid/Kconfig"
 
+source "drivers/hid/dockchannel-hid/Kconfig"
+
 endmenu
diff --git a/drivers/hid/Makefile b/drivers/hid/Makefile
index a720e68fe1d7..2c90409d515c 100644
--- a/drivers/hid/Makefile
+++ b/drivers/hid/Makefile
@@ -158,3 +158,5 @@ obj-$(CONFIG_AMD_SFH_HID)       += amd-sfh-hid/
 obj-$(CONFIG_SURFACE_HID_CORE)  += surface-hid/
 
 obj-$(CONFIG_SPI_HID_APPLE_CORE)	+= spi-hid/
+
+obj-$(CONFIG_HID_DOCKCHANNEL)	+= dockchannel-hid/
diff --git a/drivers/hid/dockchannel-hid/Kconfig b/drivers/hid/dockchannel-hid/Kconfig
new file mode 100644
index 000000000000..8a81d551a83d
--- /dev/null
+++ b/drivers/hid/dockchannel-hid/Kconfig
@@ -0,0 +1,14 @@
+# SPDX-License-Identifier: GPL-2.0-only OR MIT
+menu "DockChannel HID support"
+	depends on APPLE_DOCKCHANNEL
+
+config HID_DOCKCHANNEL
+	tristate "HID over DockChannel transport layer for Apple Silicon SoCs"
+	default ARCH_APPLE
+	depends on APPLE_DOCKCHANNEL && INPUT && OF && HID
+	help
+	  Say Y here if you use an M2 or later Apple Silicon based laptop.
+	  The keyboard and touchpad are HID based devices connected via the
+	  proprietary DockChannel interface.
+
+endmenu
diff --git a/drivers/hid/dockchannel-hid/Makefile b/drivers/hid/dockchannel-hid/Makefile
new file mode 100644
index 000000000000..7dba766b047f
--- /dev/null
+++ b/drivers/hid/dockchannel-hid/Makefile
@@ -0,0 +1,6 @@
+# SPDX-License-Identifier: GPL-2.0-only OR MIT
+#
+# Makefile for DockChannel HID transport drivers
+#
+
+obj-$(CONFIG_HID_DOCKCHANNEL)	+= dockchannel-hid.o
diff --git a/drivers/hid/dockchannel-hid/dockchannel-hid.c b/drivers/hid/dockchannel-hid/dockchannel-hid.c
new file mode 100644
index 000000000000..aaa7d357c6fa
--- /dev/null
+++ b/drivers/hid/dockchannel-hid/dockchannel-hid.c
@@ -0,0 +1,1058 @@
+/*
+ * SPDX-License-Identifier: GPL-2.0 OR MIT
+ *
+ * Apple DockChannel HID transport driver
+ *
+ * Copyright The Asahi Linux Contributors
+ */
+#include <asm/unaligned.h>
+#include <linux/delay.h>
+#include <linux/device.h>
+#include <linux/dma-mapping.h>
+#include <linux/firmware.h>
+#include <linux/gpio/consumer.h>
+#include <linux/hid.h>
+#include <linux/slab.h>
+#include <linux/soc/apple/dockchannel.h>
+#include <linux/of.h>
+#include "../hid-ids.h"
+
+#define COMMAND_TIMEOUT 1000
+
+#define MAX_INTERFACES 16
+
+/* Data + checksum */
+#define MAX_PKT_SIZE (0xffff + 4)
+
+#define DCHID_CHANNEL_CMD 0x11
+#define DCHID_CHANNEL_REPORT 0x12
+
+struct dchid_hdr {
+	u8 hdr_len;
+	u8 channel;
+	__le16 length;
+	u8 seq;
+	u8 iface;
+	__le16 pad;
+} __packed;
+
+#define IFACE_COMM 0
+
+#define FLAGS_GROUP GENMASK(7, 6)
+#define FLAGS_REQ GENMASK(5, 0)
+
+#define GROUP_INPUT 0
+#define GROUP_OUTPUT 1
+#define GROUP_CMD 2
+
+#define REQ_SET_REPORT 0
+#define REQ_GET_REPORT 1
+
+struct dchid_subhdr {
+	u8 flags;
+	u8 unk;
+	__le16 length;
+	__le32 retcode;
+} __packed;
+
+#define EVENT_GPIO_CMD	0xa0
+#define EVENT_INIT	0xf0
+#define EVENT_READY	0xf1
+
+struct dchid_init_hdr {
+	u8 type;
+	u8 unk1;
+	u8 unk2;
+	u8 iface;
+	char name[16];
+} __packed;
+
+#define INIT_HID_DESCRIPTOR	0
+#define INIT_GPIO_REQUEST	1
+#define INIT_TERMINATOR		2
+
+#define CMD_RESET_INTERFACE 0x40
+#define CMD_SEND_FIRMWARE 0x95
+#define CMD_ENABLE_INTERFACE 0xb4
+#define CMD_ACK_GPIO_CMD 0xa1
+
+struct dchid_init_block_hdr {
+	__le16 type;
+	__le16 subtype;
+	__le16 length;
+} __packed;
+
+#define MAX_GPIO_NAME 32
+
+struct dchid_gpio_request {
+	__le16 unk;
+	__le16 id;
+	char name[MAX_GPIO_NAME];
+} __packed;
+
+struct dchid_gpio_cmd {
+	u8 type;
+	u8 iface;
+	u8 gpio;
+	u8 unk;
+	u8 cmd;
+} __packed;
+
+struct dchid_gpio_ack {
+	u8 type;
+	__le32 retcode;
+	u8 cmd[];
+} __packed;
+
+#define STM_REPORT_ID		0x10
+#define STM_REPORT_SERIAL	0x11
+#define STM_REPORT_KEYBTYPE	0x14
+
+#define KEYBOARD_TYPE_ANSI	0
+#define KEYBOARD_TYPE_ISO	1
+#define KEYBOARD_TYPE_JIS	2
+
+struct dchid_stm_id {
+	u8 unk;
+	__le16 vendor_id;
+	__le16 product_id;
+	__le16 version_number;
+	u8 unk2;
+	u8 unk3;
+	u8 keyboard_type;
+	u8 serial_length;
+	/* Serial follows, but we grab it with a different report. */
+} __packed;
+
+#define FW_MAGIC 0x46444948
+#define FW_VER 1
+
+struct fw_header {
+	__le32 magic;
+	__le32 version;
+	__le32 hdr_length;
+	__le32 data_length;
+	__le32 iface_offset;
+} __packed;
+
+struct dchid_work {
+	struct work_struct work;
+	struct dchid_iface *iface;
+
+	struct dchid_hdr hdr;
+	u8 data[];
+};
+
+struct dchid_iface {
+	struct dockchannel_hid *dchid;
+	struct hid_device *hid;
+
+	int index;
+	const char *name;
+	const struct device_node *of_node;
+
+	uint8_t tx_seq;
+	uint8_t rx_seq;
+	bool deferred;
+	bool open;
+
+	void *hid_desc;
+	size_t hid_desc_len;
+
+	struct gpio_desc *gpio;
+	int gpio_id;
+
+	struct mutex out_mutex;
+	u32 out_flags;
+	int out_report;
+	u32 retcode;
+	void *resp_buf;
+	size_t resp_size;
+	struct completion out_complete;
+};
+
+struct dockchannel_hid {
+	struct device *dev;
+	struct dockchannel *dc;
+
+	bool id_ready;
+	struct dchid_stm_id device_id;
+	char serial[64];
+
+	struct dchid_iface *comm;
+	struct dchid_iface *ifaces[MAX_INTERFACES];
+
+	u8 pkt_buf[MAX_PKT_SIZE];
+
+	struct workqueue_struct *wq;
+};
+
+static struct dchid_iface *
+dchid_get_interface(struct dockchannel_hid *dchid, int index, const char *name)
+{
+	struct dchid_iface *iface;
+
+	if (index >= MAX_INTERFACES) {
+		dev_err(dchid->dev, "Interface index %d out of range\n", index);
+		return NULL;
+	}
+
+	if (dchid->ifaces[index])
+		return dchid->ifaces[index];
+
+	iface = devm_kzalloc(dchid->dev, sizeof(struct dchid_iface), GFP_KERNEL);
+	if (!iface)
+		return NULL;
+
+	iface->index = index;
+	iface->name = devm_kstrdup(dchid->dev, name, GFP_KERNEL);
+	iface->dchid = dchid;
+	iface->out_report= -1;
+	init_completion(&iface->out_complete);
+	mutex_init(&iface->out_mutex);
+
+	dev_info(dchid->dev, "Initializing interface %s\n", iface->name);
+
+	/* Comm is not a HID subdevice */
+	if (!strcmp(name, "comm")) {
+		dchid->ifaces[index] = iface;
+		return iface;
+	}
+
+	iface->of_node = of_get_child_by_name(dchid->dev->of_node, name);
+	if (!iface->of_node) {
+		dev_warn(dchid->dev, "No OF node for subdevice %s, ignoring.", name);
+		return NULL;
+	}
+
+	dchid->ifaces[index] = iface;
+	return iface;
+}
+
+static u32 dchid_checksum(void *p, size_t length)
+{
+	u32 sum = 0;
+
+	while (length >= 4) {
+		sum += get_unaligned_le32(p);
+		p += 4;
+		length -= 4;
+	}
+
+	WARN_ON_ONCE(length);
+	return sum;
+}
+
+static int dchid_send(struct dchid_iface *iface, u32 flags, void *msg, size_t size)
+{
+	u32 checksum = 0xffffffff;
+	size_t wsize = round_down(size, 4);
+	size_t tsize = size - wsize;
+	int ret;
+	struct {
+		struct dchid_hdr hdr;
+		struct dchid_subhdr sub;
+	} __packed h;
+
+	memset(&h, 0, sizeof(h));
+	h.hdr.hdr_len = sizeof(h.hdr);
+	h.hdr.channel = DCHID_CHANNEL_CMD;
+	h.hdr.length = round_up(size, 4) + sizeof(h.sub);
+	h.hdr.seq = iface->tx_seq;
+	h.hdr.iface = iface->index;
+	h.sub.flags = flags;
+	h.sub.length = size;
+
+	ret = dockchannel_send(iface->dchid->dc, &h, sizeof(h));
+	if (ret < 0)
+		return ret;
+	checksum -= dchid_checksum(&h, sizeof(h));
+
+	ret = dockchannel_send(iface->dchid->dc, msg, wsize);
+	if (ret < 0)
+		return ret;
+	checksum -= dchid_checksum(msg, wsize);
+
+	if (tsize) {
+		u8 tail[4] = {0, 0, 0, 0};
+
+		memcpy(tail, msg + wsize, tsize);
+		ret = dockchannel_send(iface->dchid->dc, tail, sizeof(tail));
+		if (ret < 0)
+			return ret;
+		checksum -= dchid_checksum(tail, sizeof(tail));
+	}
+
+	ret = dockchannel_send(iface->dchid->dc, &checksum, sizeof(checksum));
+	if (ret < 0)
+		return ret;
+
+	return 0;
+}
+
+static int dchid_cmd(struct dchid_iface *iface, u32 type, u32 req,
+		     void *data, size_t size, void *resp_buf, size_t resp_size)
+{
+	int ret;
+	int report_id = *(u8*)data;
+
+	mutex_lock(&iface->out_mutex);
+
+	WARN_ON(iface->out_report != -1);
+	iface->out_report = report_id;
+	iface->out_flags = FIELD_PREP(FLAGS_GROUP, type) | FIELD_PREP(FLAGS_REQ, req);
+	iface->resp_buf = resp_buf;
+	iface->resp_size = resp_size;
+	reinit_completion(&iface->out_complete);
+
+	ret = dchid_send(iface, iface->out_flags, data, size);
+	if (ret < 0)
+		goto done;
+
+	if (!wait_for_completion_timeout(&iface->out_complete, msecs_to_jiffies(1000))) {
+		dev_err(iface->dchid->dev, "output report 0x%x to iface  %d (%s) timed out\n",
+			report_id, iface->index, iface->name);
+		ret = -ETIMEDOUT;
+		goto done;
+	}
+
+	ret = iface->resp_size;
+	if (iface->retcode) {
+		dev_err(iface->dchid->dev,
+			"output report 0x%x to iface %d (%s) failed with err 0x%x\n",
+			report_id, iface->index, iface->name, iface->retcode);
+		ret = -EIO;
+	}
+
+done:
+	iface->tx_seq++;
+	iface->out_report = -1;
+	iface->out_flags = 0;
+	iface->resp_buf = NULL;
+	iface->resp_size = 0;
+	mutex_unlock(&iface->out_mutex);
+	return ret;
+}
+
+static int dchid_comm_cmd(struct dockchannel_hid *dchid, void *cmd, size_t size)
+{
+	return dchid_cmd(dchid->comm, GROUP_CMD, REQ_SET_REPORT, cmd, size, NULL, 0);
+}
+
+static int dchid_enable_interface(struct dchid_iface *iface)
+{
+	u8 msg[] = { CMD_ENABLE_INTERFACE, iface->index };
+
+	return dchid_comm_cmd(iface->dchid, msg, sizeof(msg));
+}
+
+static int dchid_reset_interface(struct dchid_iface *iface, int state)
+{
+	u8 msg[] = { CMD_RESET_INTERFACE, 1, iface->index, state };
+
+	return dchid_comm_cmd(iface->dchid, msg, sizeof(msg));
+}
+
+static int dchid_send_firmware(struct dchid_iface *iface, void *firmware, size_t size)
+{
+	struct {
+		u8 cmd;
+		u8 unk1;
+		u8 unk2;
+		u8 iface;
+		u64 addr;
+		u32 size;
+	} __packed msg = {
+		.cmd = CMD_SEND_FIRMWARE,
+		.unk1 = 2,
+		.unk2 = 0,
+		.iface = iface->index,
+		.size = size,
+	};
+	dma_addr_t addr;
+	void *buf = dmam_alloc_coherent(iface->dchid->dev, size, &addr, GFP_KERNEL);
+
+	if (IS_ERR_OR_NULL(buf))
+		return buf ? PTR_ERR(buf) : -ENOMEM;
+
+	msg.addr = addr;
+	memcpy(buf, firmware, size);
+	wmb();
+
+	return dchid_comm_cmd(iface->dchid, &msg, sizeof(msg));
+}
+
+static int dchid_get_firmware(struct dchid_iface *iface, void **firmware, size_t *size)
+{
+	int ret;
+	const char *fw_name;
+	const struct firmware *fw;
+	struct fw_header *hdr;
+	u8 *fw_data;
+
+	ret = of_property_read_string(iface->of_node, "firmware-name", &fw_name);
+	if (ret) {
+		/* Firmware is only for some devices */
+		*firmware = NULL;
+		*size = 0;
+		return 0;
+	}
+
+	ret = request_firmware(&fw, fw_name, iface->dchid->dev);
+	if (ret)
+		return ret;
+
+	hdr = (struct fw_header *)fw->data;
+
+	if (hdr->magic != FW_MAGIC || hdr->version != FW_VER ||
+		hdr->hdr_length < sizeof(*hdr) || hdr->hdr_length > fw->size ||
+		(hdr->hdr_length + (size_t)hdr->data_length) > fw->size ||
+		hdr->iface_offset >= hdr->data_length) {
+		dev_warn(iface->dchid->dev, "%s: invalid firmware header\n",
+			 fw_name);
+		ret = -EINVAL;
+		goto done;
+	}
+
+	fw_data = devm_kmemdup(iface->dchid->dev, fw->data + hdr->hdr_length,
+			       hdr->data_length, GFP_KERNEL);
+	if (!fw_data) {
+		ret = -ENOMEM;
+		goto done;
+	}
+
+	if (hdr->iface_offset)
+		fw_data[hdr->iface_offset] = iface->index;
+
+	*firmware = fw_data;
+	*size = hdr->data_length;
+
+done:
+	release_firmware(fw);
+	return ret;
+}
+
+
+static int dchid_start(struct hid_device *hdev)
+{
+	return 0;
+};
+
+static void dchid_stop(struct hid_device *hdev)
+{
+	/* no-op, we don't know what the shutdown commands are, if any */
+}
+
+static int dchid_open(struct hid_device *hdev)
+{
+	struct dchid_iface *iface = hdev->driver_data;
+
+	iface->open = true;
+	return 0;
+}
+
+static void dchid_close(struct hid_device *hdev)
+{
+	struct dchid_iface *iface = hdev->driver_data;
+
+	iface->open = false;
+}
+
+static int dchid_parse(struct hid_device *hdev)
+{
+	struct dchid_iface *iface = hdev->driver_data;
+
+	return hid_parse_report(hdev, iface->hid_desc, iface->hid_desc_len);
+}
+
+/* Note: buf excludes report number! For ease of fetching strings/etc. */
+static int dchid_get_report_cmd(struct dchid_iface *iface, u8 reportnum, void *buf, size_t len)
+{
+	int ret = dchid_cmd(iface, GROUP_CMD, REQ_GET_REPORT, &reportnum, 1, buf, len);
+
+	return ret <= 0 ? ret : ret - 1;
+}
+
+/* Note: buf includes report number! */
+static int dchid_set_report(struct dchid_iface *iface, void *buf, size_t len)
+{
+	return dchid_cmd(iface, GROUP_OUTPUT, REQ_SET_REPORT, buf, len, NULL, 0);
+}
+
+static int dchid_raw_request(struct hid_device *hdev,
+				unsigned char reportnum, __u8 *buf, size_t len,
+				unsigned char rtype, int reqtype)
+{
+	struct dchid_iface *iface = hdev->driver_data;
+
+	switch (reqtype) {
+	case HID_REQ_GET_REPORT:
+		buf[0] = reportnum;
+		return dchid_cmd(iface, GROUP_OUTPUT, REQ_GET_REPORT, &reportnum, 1, buf + 1, len - 1);
+	case HID_REQ_SET_REPORT:
+		return dchid_set_report(iface, buf, len);
+	default:
+		return -EIO;
+	}
+
+	return 0;
+}
+
+static struct hid_ll_driver dchid_ll = {
+	.start = &dchid_start,
+	.stop = &dchid_stop,
+	.open = &dchid_open,
+	.close = &dchid_close,
+	.parse = &dchid_parse,
+	.raw_request = &dchid_raw_request,
+};
+
+static void dchid_init_interface(struct dchid_iface *iface)
+{
+	void *fw;
+	size_t size;
+
+	iface->deferred = false;
+
+	/* Enable interface (general) */
+	if (dchid_enable_interface(iface) < 0)
+		return;
+
+	/* Look to see if we need firmware */
+	if (dchid_get_firmware(iface, &fw, &size) < 0)
+		return;
+
+	/* Only multi-touch has firmware */
+	if (!fw || !size)
+		return;
+
+	/* Send it to the device */
+	if (dchid_send_firmware(iface, fw, size) < 0)
+		return;
+
+	/* After loading firmware, multi-touch needs a reset */
+	dchid_reset_interface(iface, 0);
+	dchid_reset_interface(iface, 2);
+}
+
+static void dchid_handle_descriptor(struct dchid_iface *iface, void *hid_desc, size_t desc_len)
+{
+	if (iface->hid) {
+		dev_warn(iface->dchid->dev, "Tried to initialize already started interface %s!\n",
+			 iface->name);
+		return;
+	}
+
+	iface->hid_desc = devm_kmemdup(iface->dchid->dev, hid_desc, desc_len, GFP_KERNEL);
+	if (!iface->hid_desc)
+		return;
+
+	iface->hid_desc_len = desc_len;
+
+	/* We need to enable STM first, since it'll give us the device IDs */
+	if (iface->dchid->id_ready || !strcmp(iface->name, "stm"))
+		dchid_init_interface(iface);
+	else
+		iface->deferred = true;
+}
+
+static void dchid_handle_ready(struct dockchannel_hid *dchid, void *data, size_t length)
+{
+	struct hid_device *hid;
+	struct dchid_iface *iface;
+	int ret;
+	u8 *pkt = data;
+	u8 index;
+	int i;
+
+	if (length < 2) {
+		dev_err(dchid->dev, "Bad length for ready message: %ld\n", length);
+		return;
+	}
+
+	index = pkt[1];
+
+	if (index >= MAX_INTERFACES) {
+		dev_err(dchid->dev, "Got ready notification for bad iface %d\n", index);
+		return;
+	}
+
+	iface = dchid->ifaces[index];
+	if (!iface) {
+		dev_err(dchid->dev, "Got ready notification for unknown iface %d\n", index);
+		return;
+	}
+
+	if (iface->hid) {
+		dev_warn(iface->dchid->dev, "Interface %s already ready!\n",
+			 iface->name);
+		return;
+	}
+
+	/* When STM is ready, grab global device info */
+	if (!strcmp(iface->name, "stm")) {
+		ret = dchid_get_report_cmd(iface, STM_REPORT_ID, &dchid->device_id,
+					   sizeof(dchid->device_id));
+		if (ret < sizeof(dchid->device_id)) {
+			dev_warn(iface->dchid->dev, "Failed to get device ID from STM!\n");
+			/* Fake it and keep going. Things might still work... */
+			memset(&dchid->device_id, 0, sizeof(dchid->device_id));
+			dchid->device_id.vendor_id = HOST_VENDOR_ID_APPLE;
+		}
+		ret = dchid_get_report_cmd(iface, STM_REPORT_SERIAL, dchid->serial,
+					   sizeof(dchid->serial) - 1);
+		if (ret < 0) {
+			dev_warn(iface->dchid->dev, "Failed to get serial from STM!\n");
+			dchid->serial[0] = 0;
+		}
+
+		dchid->id_ready = true;
+		for (i = 0; i < MAX_INTERFACES; i++)
+			if (dchid->ifaces[i] && dchid->ifaces[i]->deferred)
+				dchid_init_interface(dchid->ifaces[i]);
+
+	}
+
+	hid = hid_allocate_device();
+	if (IS_ERR(hid))
+		return;
+
+	snprintf(hid->name, sizeof(hid->name), "Apple MTP %s", iface->name);
+	snprintf(hid->phys, sizeof(hid->phys), "%s.%d (%s)",
+		 dev_name(iface->dchid->dev), iface->index, iface->name);
+	strscpy(hid->uniq, dchid->serial, sizeof(hid->uniq));
+
+	hid->ll_driver = &dchid_ll;
+	hid->bus = BUS_HOST;
+	hid->vendor = dchid->device_id.vendor_id;
+	hid->product = dchid->device_id.product_id;
+	hid->version = dchid->device_id.version_number;
+	hid->type = HID_TYPE_OTHER;
+	if (!strcmp(iface->name, "multi-touch")) {
+		hid->type = HID_TYPE_SPI_MOUSE;
+	} else if (!strcmp(iface->name, "keyboard")) {
+		hid->type = HID_TYPE_SPI_KEYBOARD;
+
+		/* These country codes match what earlier Apple HID keyboards did */
+		switch (dchid->device_id.keyboard_type) {
+		case KEYBOARD_TYPE_ANSI:
+			hid->country = 33; // US-English
+			break;
+
+		case KEYBOARD_TYPE_ISO:
+			hid->country = 13; // ISO
+			break;
+
+		case KEYBOARD_TYPE_JIS:
+			hid->country = 15; // Japan
+			break;
+		}
+	}
+
+	hid->dev.parent = iface->dchid->dev;
+	hid->driver_data = iface;
+
+	ret = hid_add_device(hid);
+	if (ret < 0) {
+		hid_destroy_device(hid);
+		dev_warn(iface->dchid->dev, "Failed to register hid device %s", iface->name);
+		return;
+	}
+
+	iface->hid = hid;
+}
+
+static void dchid_request_gpio(struct dchid_iface *iface, int id, const char *name)
+{
+	char prop_name[MAX_GPIO_NAME + 16];
+
+	dev_info(iface->dchid->dev, "Requesting GPIO %s#%d: %s\n", iface->name, id, name);
+
+	if (iface->gpio) {
+		dev_err(iface->dchid->dev, "Cannot request more than one GPIO per interface!\n");
+		return;
+	}
+
+	snprintf(prop_name, sizeof(prop_name), "apple,%s-gpios", name);
+
+	iface->gpio = devm_gpiod_get_from_of_node(iface->dchid->dev,
+						  iface->of_node, prop_name, 0,
+						  GPIOD_OUT_LOW, name);
+
+	if (IS_ERR_OR_NULL(iface->gpio)) {
+		dev_err(iface->dchid->dev, "Failed to request GPIO %s\n", prop_name);
+		iface->gpio = NULL;
+		return;
+	}
+
+	iface->gpio_id = id;
+}
+
+static void dchid_handle_init(struct dockchannel_hid *dchid, void *data, size_t length)
+{
+	struct dchid_init_hdr *hdr = data;
+	struct dchid_iface *iface;
+	struct dchid_init_block_hdr *blk;
+
+	if (length < sizeof(*hdr))
+		return;
+
+	iface = dchid_get_interface(dchid, hdr->iface, hdr->name);
+	if (!iface)
+		return;
+
+	data += sizeof(*hdr);
+	length -= sizeof(*hdr);
+
+	while (length > sizeof(*blk)) {
+		blk = data;
+		data += sizeof(*blk);
+		length -= sizeof(*blk);
+
+		if (blk->length > length)
+			return;
+		switch (blk->type) {
+		case INIT_HID_DESCRIPTOR:
+			dchid_handle_descriptor(iface, data, blk->length);
+			break;
+
+		case INIT_GPIO_REQUEST: {
+			struct dchid_gpio_request *req = data;
+
+			if (sizeof(*req) > length)
+				return;
+			dchid_request_gpio(iface, req->id, req->name);
+			break;
+		}
+
+		case INIT_TERMINATOR:
+			return;
+		}
+
+		data += blk->length + sizeof(*blk);
+		length -= blk->length + sizeof(*blk);
+	}
+}
+
+static void dchid_handle_gpio(struct dockchannel_hid *dchid, void *data, size_t length)
+{
+	struct dchid_gpio_cmd *cmd = data;
+	struct dchid_iface *iface;
+	u32 retcode = 0xe000f00d; /* Give it a random Apple-style error code */
+	struct dchid_gpio_ack *ack;
+
+	if (length < sizeof(*cmd))
+		return;
+
+	if (cmd->iface >= MAX_INTERFACES || !(iface = dchid->ifaces[cmd->iface])) {
+		dev_err(dchid->dev, "Got GPIO command for bad inteface %d\n", cmd->iface);
+		goto err;
+	}
+
+	if (!iface->gpio || cmd->gpio != iface->gpio_id) {
+		dev_err(dchid->dev, "Got GPIO command for bad GPIO %s#%d\n",
+			iface->name, cmd->gpio);
+		goto err;
+	}
+
+	dev_info(dchid->dev, "GPIO command: %s#%d: %d\n", iface->name, cmd->gpio, cmd->cmd);
+
+	switch (cmd->cmd) {
+	case 3:
+		/* Pulse.  */
+		gpiod_set_value_cansleep(iface->gpio, 1);
+		msleep(10); /* Random guess... */
+		gpiod_set_value_cansleep(iface->gpio, 0);
+		retcode = 0;
+		break;
+	default:
+		dev_err(dchid->dev, "Unknown GPIO command %d\n", cmd->cmd	);
+		break;
+	}
+
+err:
+	/* Ack it */
+	ack = kzalloc(sizeof(*ack) + length, GFP_KERNEL);
+	if (!ack)
+		return;
+
+	ack->type = CMD_ACK_GPIO_CMD;
+	ack->retcode = retcode;
+	memcpy(ack->cmd, data, length);
+
+	if (dchid_comm_cmd(dchid, ack, sizeof(*ack) + length) < 0)
+		dev_err(dchid->dev, "Failed to ACK GPIO command\n");
+
+	kfree(ack);
+}
+
+static void dchid_handle_event(struct dockchannel_hid *dchid, void *data, size_t length)
+{
+	u8 *p = data;
+	switch (*p) {
+	case EVENT_INIT:
+		dchid_handle_init(dchid, data, length);
+		break;
+	case EVENT_READY:
+		dchid_handle_ready(dchid, data, length);
+		break;
+	case EVENT_GPIO_CMD:
+		dchid_handle_gpio(dchid, data, length);
+		break;
+	}
+}
+
+static void dchid_handle_report(struct dchid_iface *iface, void *data, size_t length)
+{
+	struct dockchannel_hid *dchid = iface->dchid;
+
+	if (!iface->hid) {
+		dev_warn(dchid->dev, "Report received but %s is not initialized!\n", iface->name);
+		return;
+	}
+
+	if (!iface->open)
+		return;
+
+	hid_input_report(iface->hid, HID_INPUT_REPORT, data, length, 1);
+}
+
+static void dchid_packet_work(struct work_struct *ws)
+{
+	struct dchid_work *work = container_of(ws, struct dchid_work, work);
+	struct dchid_subhdr *shdr = (void *)work->data;
+	struct dockchannel_hid *dchid = work->iface->dchid;
+	int type = FIELD_GET(FLAGS_GROUP, shdr->flags);
+	u8 *payload = work->data + sizeof(*shdr);
+
+	if (shdr->length + sizeof(*shdr) > work->hdr.length) {
+		dev_err(dchid->dev, "Bad sub header length (%d > %ld)\n",
+			shdr->length, work->hdr.length - sizeof(*shdr));
+		return;
+	}
+
+	switch (type) {
+	case GROUP_INPUT:
+		if (work->hdr.iface == IFACE_COMM)
+			dchid_handle_event(dchid, payload, shdr->length);
+		else
+			dchid_handle_report(work->iface, payload, shdr->length);
+		break;
+	default:
+		dev_err(dchid->dev, "Received unknown packet type %d\n", type);
+		break;
+	}
+
+	kfree(work);
+}
+
+static void dchid_handle_ack(struct dchid_iface *iface, struct dchid_hdr *hdr, void *data)
+{
+	struct dchid_subhdr *shdr = (void *)data;
+	u8 *payload = data + sizeof(*shdr);
+
+	if (shdr->length + sizeof(*shdr) > hdr->length) {
+		dev_err(iface->dchid->dev, "Bad sub header length (%d > %ld)\n",
+			shdr->length, hdr->length - sizeof(*shdr));
+		return;
+	}
+	if (shdr->flags != iface->out_flags) {
+		dev_err(iface->dchid->dev,
+			"Received unexpected flags 0x%x on ACK channel (expected 0x%x)\n",
+			shdr->flags, iface->out_flags);
+		return;
+	}
+
+	if (shdr->length < 1) {
+		dev_err(iface->dchid->dev, "Received length 0 output report ack\n");
+		return;
+	}
+	if (iface->tx_seq != hdr->seq) {
+		dev_err(iface->dchid->dev, "Received ACK with bad seq (expected %d, got %d)\n",
+			iface->rx_seq, hdr->seq);
+		return;
+	}
+	if (iface->out_report != payload[0]) {
+		dev_err(iface->dchid->dev, "Received ACK with bad report (expected %d, got %d\n",
+			iface->out_report, payload[0]);
+		return;
+	}
+
+	if (iface->resp_buf && iface->resp_size)
+		memcpy(iface->resp_buf, payload + 1, min((size_t)shdr->length - 1, iface->resp_size));
+
+	iface->resp_size = shdr->length;
+	iface->out_report = -1;
+	iface->retcode = shdr->retcode;
+	complete(&iface->out_complete);
+}
+
+static void dchid_handle_packet(void *cookie, size_t avail)
+{
+	struct dockchannel_hid *dchid = cookie;
+	struct dchid_hdr hdr;
+	struct dchid_work *work;
+	struct dchid_iface *iface;
+	u32 checksum;
+
+	if (dockchannel_recv(dchid->dc, &hdr, sizeof(hdr)) != sizeof(hdr)) {
+		dev_err(dchid->dev, "Read failed (header)\n");
+		return;
+	}
+
+	if (hdr.hdr_len != sizeof(hdr)) {
+		dev_err(dchid->dev, "Bad header length %d\n", hdr.hdr_len);
+		goto done;
+	}
+
+	if (dockchannel_recv(dchid->dc, dchid->pkt_buf, hdr.length + 4) != (hdr.length + 4)) {
+		dev_err(dchid->dev, "Read failed (body)\n");
+		goto done;
+	}
+
+	checksum = dchid_checksum(&hdr, sizeof(hdr));
+	checksum += dchid_checksum(dchid->pkt_buf, hdr.length + 4);
+
+	if (checksum != 0xffffffff) {
+		dev_err(dchid->dev, "Checksum mismatch (iface %d): 0x%08x != 0xffffffff\n",
+			hdr.iface, checksum);
+		goto done;
+	}
+
+
+	if (hdr.iface >= MAX_INTERFACES) {
+		dev_err(dchid->dev, "Bad iface %d\n", hdr.iface);
+	}
+
+	iface = dchid->ifaces[hdr.iface];
+
+	if (!iface) {
+		dev_err(dchid->dev, "Received packet for uninitialized iface %d\n", hdr.iface);
+		goto done;
+	}
+
+	switch (hdr.channel) {
+		case DCHID_CHANNEL_CMD:
+			dchid_handle_ack(iface, &hdr, dchid->pkt_buf);
+			goto done;
+		case DCHID_CHANNEL_REPORT:
+			break;
+		default:
+			dev_warn(dchid->dev, "Unknown channel 0x%x, treating as report...\n",
+				 hdr.channel);
+			break;
+	}
+
+	if (hdr.seq != iface->rx_seq) {
+		dev_err(dchid->dev, "Received packet out of sequence (expected %d, got %d)\n",
+			iface->rx_seq, hdr.seq);
+		goto done;
+	}
+
+	iface->rx_seq++;
+
+	work = kzalloc(sizeof(*work) + hdr.length, GFP_KERNEL);
+	if (!work)
+		return;
+
+	work->hdr = hdr;
+	work->iface = iface;
+	memcpy(work->data, dchid->pkt_buf, hdr.length);
+	INIT_WORK(&work->work, dchid_packet_work);
+
+	queue_work(dchid->wq, &work->work);
+
+done:
+	dockchannel_await(dchid->dc, dchid_handle_packet, dchid, sizeof(struct dchid_hdr));
+}
+
+static int dockchannel_hid_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct dockchannel_hid *dchid;
+	struct device_node *child;
+	struct property *prop;
+	bool defer = false;
+
+	/*
+	 * First make sure all the GPIOs are available, in cased we need to defer.
+	 * This is necessary because MTP will request them by name later, and by then
+	 * it's too late to defer the probe.
+	 */
+
+	for_each_child_of_node(dev->of_node, child) {
+		for_each_property_of_node(child, prop) {
+			size_t len = strlen(prop->name);
+			struct gpio_desc *gpio;
+
+			if (len < 12 || strncmp("apple,", prop->name, 6) ||
+			    strcmp("-gpios", prop->name + len - 6))
+				continue;
+
+			gpio = gpiod_get_from_of_node(child, prop->name, 0, GPIOD_ASIS,
+						      prop->name);
+			if (IS_ERR_OR_NULL(gpio)) {
+				if (PTR_ERR(gpio) == EPROBE_DEFER) {
+					defer = true;
+					of_node_put(child);
+					return -EPROBE_DEFER;
+				}
+			} else {
+				gpiod_put(gpio);
+			}
+		}
+	}
+
+	dchid = devm_kzalloc(dev, sizeof(*dchid), GFP_KERNEL);
+	if (!dchid)
+		return -ENOMEM;
+
+
+	dchid->dev = &pdev->dev;
+	dchid->dc = dockchannel_init(pdev);
+	if (IS_ERR_OR_NULL(dchid->dc)) {
+		return -PTR_ERR(dchid->dc);
+	}
+
+	dchid->comm = dchid_get_interface(dchid, IFACE_COMM, "comm");
+	if (!dchid->comm) {
+		dev_err(dchid->dev, "Failed to initialize comm interface");
+		return -EIO;
+	}
+
+	dchid->wq = alloc_ordered_workqueue("dockchannel-hid-report", WQ_MEM_RECLAIM);
+	if (!dchid->wq)
+		return -ENOMEM;
+
+	dev_info(dchid->dev, "initialized, awaiting packets\n");
+	dockchannel_await(dchid->dc, dchid_handle_packet, dchid, sizeof(struct dchid_hdr));
+
+	return 0;
+}
+
+static int dockchannel_hid_remove(struct platform_device *pdev)
+{
+	BUG_ON(1);
+	return 0;
+}
+
+static const struct of_device_id dockchannel_hid_of_match[] = {
+	{ .compatible = "apple,dockchannel-hid" },
+	{},
+};
+MODULE_DEVICE_TABLE(of, dockchannel_hid_of_match);
+MODULE_FIRMWARE("apple/tpmtfw-*.bin");
+
+static struct platform_driver dockchannel_hid_driver = {
+	.driver = {
+		.name = "dockchannel-hid",
+		.of_match_table = dockchannel_hid_of_match,
+	},
+	.probe = dockchannel_hid_probe,
+	.remove = dockchannel_hid_remove,
+};
+module_platform_driver(dockchannel_hid_driver);
+
+MODULE_DESCRIPTION("Apple DockChannel HID transport driver");
+MODULE_AUTHOR("Hector Martin <marcan@marcan.st>");
+MODULE_LICENSE("Dual MIT/GPL");
-- 
2.34.1