From b7ddb7c7c077a0ca8eb095f4df2c066eb29c2b43 Mon Sep 17 00:00:00 2001
From: dragonmux <git@dragonmux.network>
Date: Thu, 11 Aug 2022 07:52:43 +0100
Subject: [PATCH] usb: Implemented support for sending the Microsoft
 OS-specific descriptor component of a platform capability descriptor

---
 include/libopencm3/usb/bos.h       |  4 ++++
 include/libopencm3/usb/microsoft.h | 11 +++++++++++
 lib/usb/usb_standard.c             | 12 +++++++++++-
 3 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/include/libopencm3/usb/bos.h b/include/libopencm3/usb/bos.h
index b128f9f1..4e5325e6 100644
--- a/include/libopencm3/usb/bos.h
+++ b/include/libopencm3/usb/bos.h
@@ -87,6 +87,8 @@ typedef struct __attribute__((packed)) usb_bos_uuid {
 	uint8_t e[6];
 } usb_bos_uuid;
 
+#define USB_BOS_UUID_SIZE sizeof(usb_bos_uuid)
+
 typedef struct usb_device_capability_descriptor {
 	uint8_t bLength;
 	uint8_t bDescriptorType;
@@ -125,6 +127,8 @@ typedef struct __attribute__((packed)) usb_platform_device_capability_descriptor
 	usb_bos_uuid PlatformCapabilityUUID;
 
 	/* Descriptor ends here.  The following are used internally: */
+	/* This is a type-erased struct of the platform-specific capability data */
+	const void *CapabilityData;
 } usb_platform_device_capability_descriptor;
 
 #define USB_DCT_PLATFORM_SIZE 20U
diff --git a/include/libopencm3/usb/microsoft.h b/include/libopencm3/usb/microsoft.h
index d81879ed..15cc072a 100644
--- a/include/libopencm3/usb/microsoft.h
+++ b/include/libopencm3/usb/microsoft.h
@@ -76,6 +76,17 @@ enum microsoft_registry_types {
 	{0x65U, 0x9dU, 0x9eU, 0x64U, 0x8aU, 0x9fU}, \
 }
 
+#define MICROSOFT_WINDOWS_VERSION_WINBLUE 0x06030000
+
+typedef struct microsoft_os_descriptor_set_information {
+	uint32_t dwWindowsVersion;
+	uint16_t wMSOSDescriptorSetTotalLength;
+	uint8_t bMS_VendorCode;
+	uint8_t bAltEnumCode;
+} microsoft_os_descriptor_set_information;
+
+#define MICROSOFT_OS_DESCRIPTOR_SET_INFORMATION_SIZE sizeof(microsoft_os_descriptor_set_information)
+
 #endif
 
 /**@}*/
diff --git a/lib/usb/usb_standard.c b/lib/usb/usb_standard.c
index b252b3c3..938c4aea 100644
--- a/lib/usb/usb_standard.c
+++ b/lib/usb/usb_standard.c
@@ -38,8 +38,12 @@ LGPL License Terms @ref lgpl_license
 #include <string.h>
 #include <libopencm3/usb/usbd.h>
 #include <libopencm3/usb/bos.h>
+#include <libopencm3/usb/microsoft.h>
 #include "usb_private.h"
 
+static const usb_bos_uuid microsoft_os_descriptor_platform_capability_id =
+	MICROSOFT_OS_DESCRIPTOR_PLATFORM_CAPABILITY_ID;
+
 int usbd_register_set_config_callback(usbd_device *usbd_dev,
 				       usbd_set_config_callback callback)
 {
@@ -149,8 +153,14 @@ static uint16_t build_devcap_platform(const usb_platform_device_capability_descr
 	len -= count;
 	const uint16_t total = count;
 
+	if (!memcmp(&plat->PlatformCapabilityUUID, &microsoft_os_descriptor_platform_capability_id, USB_BOS_UUID_SIZE)) {
+		const microsoft_os_descriptor_set_information *info = plat->CapabilityData;
+		count = MIN(len, MICROSOFT_OS_DESCRIPTOR_SET_INFORMATION_SIZE);
+		memcpy(buf + total, info, count);
+		return total + count;
+	}
 
-	return total;
+	return 0;
 }
 
 /* This can return 0 to indicate an error in the descriptor */