Add WebUSB descriptor support

The WebUSB specification defines a specific Platform Descriptor in the
Binary Object Store:
https://wicg.github.io/webusb/#webusb-platform-capability-descriptor
This descriptor provides a special 'Landing page' URL to the host
browser and associated privileges for it.

Bump the USB version for BOS descriptors to 2.1 to be compatible with
Chrome implementation.

Signed-off-by: Vincent Palatin <vpalatin@chromium.org>

BUG=none
BRANCH=twinkie
TEST=manual: on Twinkie (chip/stm32) and HG proto2 (chip/g), enumerate
WebUSB descriptors with lsusb and connect to a WebUSB page in Chrome
R61+.

Change-Id: I7211ab554f4a6c156c1e8e79a3d9f0d6644217c6
Reviewed-on: https://chromium-review.googlesource.com/664813
Commit-Ready: Vincent Palatin <vpalatin@chromium.org>
Tested-by: Vincent Palatin <vpalatin@chromium.org>
Reviewed-by: Vincent Palatin <vpalatin@chromium.org>
(cherry picked from commit 77f011206c87a7a3e8cd93d3635c6c4f0ea3e32d)
Reviewed-on: https://chromium-review.googlesource.com/828415
Commit-Queue: Vadim Bendebury <vbendeb@chromium.org>
Tested-by: Vadim Bendebury <vbendeb@chromium.org>
Reviewed-by: Vadim Bendebury <vbendeb@chromium.org>

6 files changed, 163 insertions, 21 deletions

diff --git a/chip/g/usb.c b/chip/g/usb.c
index ea791fa15a..00b1e8df8c 100644
--- a/chip/g/usb.c
+++ b/chip/g/usb.c
@@ -186,8 +186,8 @@ static void showregs(void)
 /* Standard USB stuff */
 
 #ifdef CONFIG_USB_BOS
-/* v2.01 (vs 2.00) BOS Descriptor provided */
-#define USB_DEV_BCDUSB 0x0201
+/* v2.10 (vs 2.00) BOS Descriptor provided */
+#define USB_DEV_BCDUSB 0x0210
 #else
 #define USB_DEV_BCDUSB 0x0200
 #endif
@@ -822,6 +822,20 @@ static void handle_setup(enum table_case tc)
 			print_later("  iface returned %d", bytes, 0, 0, 0, 0);
 		}
 	} else {
+#ifdef CONFIG_WEBUSB_URL
+		if (data_phase_in &&
+		    ((req->bmRequestType & USB_TYPE_MASK) == USB_TYPE_VENDOR)) {
+			if (req->bRequest == 0x01 &&
+			    req->wIndex == WEBUSB_REQ_GET_URL) {
+				bytes = *(uint8_t *)webusb_url;
+				bytes = MIN(req->wLength, bytes);
+				if (load_in_fifo(webusb_url, bytes) < 0)
+					bytes = -1;
+			} else {
+				report_error(-1);
+			}
+		} else
+#endif
 		/* Something we need to add support for? */
 		report_error(-1);
 	}
diff --git a/chip/stm32/usb.c b/chip/stm32/usb.c
index 2afab3f415..a179461af5 100644
--- a/chip/stm32/usb.c
+++ b/chip/stm32/usb.c
@@ -112,6 +112,29 @@ void usb_read_setup_packet(usb_uint *buffer, struct usb_setup_packet *packet)
 	packet->wLength       = buffer[3];
 }
 
+static void ep0_send_descriptor(const uint8_t *desc, int len,
+				uint16_t fixup_size)
+{
+	/* do not send more than what the host asked for */
+	len = MIN(ep0_buf_rx[3], len);
+	/*
+	 * if we cannot transmit everything at once,
+	 * keep the remainder for the next IN packet
+	 */
+	if (len >= USB_MAX_PACKET_SIZE) {
+		desc_left = len - USB_MAX_PACKET_SIZE;
+		desc_ptr = desc + USB_MAX_PACKET_SIZE;
+		len = USB_MAX_PACKET_SIZE;
+	}
+	memcpy_to_usbram(EP0_BUF_TX_SRAM_ADDR, desc, len);
+	if (fixup_size) /* set the real descriptor size */
+		ep0_buf_tx[1] = fixup_size;
+	btable_ep[0].tx_count = len;
+	/* send the null OUT transaction if the transfer is complete */
+	STM32_TOGGLE_EP(0, EP_TX_RX_MASK, EP_TX_RX_VALID,
+			desc_left ? 0 : EP_STATUS_OUT);
+}
+
 /* Requests on the control endpoint (aka EP0) */
 static void ep0_rx(void)
 {
@@ -135,6 +158,21 @@ static void ep0_rx(void)
 			return;
 		}
 	}
+	/* vendor specific request */
+	if ((req & USB_TYPE_MASK) == USB_TYPE_VENDOR) {
+#ifdef CONFIG_WEBUSB_URL
+		uint8_t b_req = req >> 8; /* bRequest in the transfer */
+		uint16_t idx = ep0_buf_rx[2]; /* wIndex in the transfer */
+
+		if (b_req == 0x01 && idx == WEBUSB_REQ_GET_URL) {
+			int len = *(uint8_t *)webusb_url;
+
+			ep0_send_descriptor(webusb_url, len, 0);
+			return;
+		}
+#endif
+		goto unknown_req;
+	}
 
 	/* TODO check setup bit ? */
 	if (req == (USB_DIR_IN | (USB_REQ_GET_DESCRIPTOR << 8))) {
@@ -176,25 +214,8 @@ static void ep0_rx(void)
 		default: /* unhandled descriptor */
 			goto unknown_req;
 		}
-		/* do not send more than what the host asked for */
-		len = MIN(ep0_buf_rx[3], len);
-		/*
-		 * if we cannot transmit everything at once,
-		 * keep the remainder for the next IN packet
-		 */
-		if (len >= USB_MAX_PACKET_SIZE) {
-			desc_left = len - USB_MAX_PACKET_SIZE;
-			desc_ptr = desc + USB_MAX_PACKET_SIZE;
-			len = USB_MAX_PACKET_SIZE;
-		}
-		memcpy_to_usbram(EP0_BUF_TX_SRAM_ADDR, desc, len);
-		if (type == USB_DT_CONFIGURATION)
-			/* set the real descriptor size */
-			ep0_buf_tx[1] = USB_DESC_SIZE;
-		btable_ep[0].tx_count = len;
-		STM32_TOGGLE_EP(0, EP_TX_RX_MASK, EP_TX_RX_VALID,
-				desc_left ? 0 : EP_STATUS_OUT);
-		/* send the null OUT transaction if the transfer is complete */
+		ep0_send_descriptor(desc, len, type == USB_DT_CONFIGURATION ?
+						USB_DESC_SIZE : 0);
 	} else if (req == (USB_DIR_IN | (USB_REQ_GET_STATUS << 8))) {
 		uint16_t zero = 0;
 		/* Get status */
diff --git a/common/build.mk b/common/build.mk
index ef41886133..ae48325949 100644
--- a/common/build.mk
+++ b/common/build.mk
@@ -107,6 +107,7 @@ common-$(CONFIG_USB_PD_TCPC)+=usb_pd_tcpc.o
 common-$(CONFIG_USB_UPDATE)+=usb_update.o update_fw.o
 common-$(CONFIG_VBOOT_HASH)+=sha256.o vboot_hash.o
 common-$(CONFIG_VSTORE)+=vstore.o
+common-$(CONFIG_WEBUSB_URL)+=webusb_desc.o
 common-$(CONFIG_WIRELESS)+=wireless.o
 common-$(HAS_TASK_CHIPSET)+=chipset.o
 common-$(HAS_TASK_CONSOLE)+=console.o console_output.o uart_buffering.o
diff --git a/common/webusb_desc.c b/common/webusb_desc.c
new file mode 100644
index 0000000000..41d39006e0
--- /dev/null
+++ b/common/webusb_desc.c
@@ -0,0 +1,46 @@
+/* Copyright 2017 The Chromium OS Authors. All rights reserved.
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+/* WebUSB platform descriptor */
+
+#include "common.h"
+#include "usb_descriptor.h"
+#include "util.h"
+
+#ifndef CONFIG_USB_BOS
+#error "CONFIG_USB_BOS must be defined to use WebUSB descriptor"
+#endif
+
+const void *webusb_url = USB_URL_DESC(HTTPS, CONFIG_WEBUSB_URL);
+
+/*
+ * Platform Descriptor in the device Binary Object Store
+ * as defined by USB 3.1 spec chapter 9.6.2.
+ */
+static struct {
+	struct usb_bos_hdr_descriptor bos;
+	struct usb_platform_descriptor platform;
+} bos_desc = {
+	.bos = {
+		.bLength = USB_DT_BOS_SIZE,
+		.bDescriptorType = USB_DT_BOS,
+		.wTotalLength = (USB_DT_BOS_SIZE + USB_DT_PLATFORM_SIZE),
+		.bNumDeviceCaps = 1,  /* platform caps */
+	},
+	.platform = {
+		.bLength = USB_DT_PLATFORM_SIZE,
+		.bDescriptorType = USB_DT_DEVICE_CAPABILITY,
+		.bDevCapabilityType = USB_DC_DTYPE_PLATFORM,
+		.bReserved = 0,
+		.PlatformCapUUID = USB_PLAT_CAP_WEBUSB,
+		.bcdVersion = 0x0100,
+		.bVendorCode = 0x01,
+		.iLandingPage = 1,
+	},
+};
+
+const struct bos_context bos_ctx = {
+	.descp = (void *)&bos_desc,
+	.size = sizeof(bos_desc),
+};
diff --git a/include/config.h b/include/config.h
index 7206555113..4a7b82ab45 100644
--- a/include/config.h
+++ b/include/config.h
@@ -2537,6 +2537,18 @@
 #define CONFIG_AUX_TIMER_PERIOD_MS (CONFIG_WATCHDOG_PERIOD_MS - 500)
 
 /*****************************************************************************/
+/* WebUSB config */
+
+/*
+ * Enable the WebUSB support and define its URL.
+ * Export a WebUSB Platform Descriptor in the Binary Object Store descriptor.
+ * The WebUSB landing page URL is equal to 'CONFIG_WEBUSB_URL' plus the
+ * https:// prefix.
+ * This requires CONFIG_USB_BOS.
+ */
+#undef CONFIG_WEBUSB_URL
+
+/*****************************************************************************/
 
 /*
  * Support controlling power to WiFi, WWAN (3G/LTE), and/or bluetooth modules.
diff --git a/include/usb_descriptor.h b/include/usb_descriptor.h
index 0493f4f558..24d5676cfc 100644
--- a/include/usb_descriptor.h
+++ b/include/usb_descriptor.h
@@ -89,6 +89,24 @@ struct usb_contid_caps_descriptor {
 #define USB_DC_DTYPE_BILLBOARD 0x0d
 /* RESERVED 0x00, 0xOe - 0xff */
 
+/* Platform descriptor */
+struct usb_platform_descriptor {
+	uint8_t  bLength;
+	uint8_t  bDescriptorType;     /* USB_DT_DEVICE_CAPABILITY */
+	uint8_t  bDevCapabilityType;  /* USB_DC_DTYPE_PLATFORM */
+	uint8_t  bReserved;           /* SBZ */
+	uint8_t  PlatformCapUUID[16]; /* USB_PLAT_CAP_xxx */
+	uint16_t bcdVersion;          /* 0x0100 */
+	uint8_t  bVendorCode;
+	uint8_t  iLandingPage;
+} __packed;
+#define USB_DT_PLATFORM_SIZE   24
+
+/* Platform Capability UUIDs */
+#define USB_PLAT_CAP_WEBUSB /*{3408b638-09a9-47a0-8bfd-a0768815b665}*/ \
+	{0x38, 0xB6, 0x08, 0x34, 0xA9, 0x09, 0xA0, 0x47,               \
+	 0x8B, 0xFD, 0xA0, 0x76, 0x88, 0x15, 0xB6, 0x65}
+
 /* Qualifier Descriptor */
 struct usb_qualifier_descriptor {
 	uint8_t  bLength;
@@ -225,6 +243,35 @@ struct usb_endpoint_descriptor {
 #define USB_REQ_SET_INTERFACE      0x0B
 #define USB_REQ_SYNCH_FRAME        0x0C
 
+/* WebUSB URL descriptors */
+#define WEBUSB_REQ_GET_URL         0x02
+#define USB_DT_WEBUSB_URL          0x03
+
+#define USB_URL_SCHEME_HTTP       0x00
+#define USB_URL_SCHEME_HTTPS      0x01
+#define USB_URL_SCHEME_NONE       0xff
+
+/*
+ * URL descriptor helper.
+ * (similar to string descriptor but UTF-8 instead of UTF-16)
+ */
+#define USB_URL_DESC(scheme, str) \
+	(const void *)&(const struct { \
+		uint8_t _len; \
+		uint8_t _type; \
+		uint8_t _scheme; \
+		char _data[sizeof(str)]; \
+	}) { \
+		/* Total size of the descriptor is : \
+		 * size of the UTF-8 text plus the len/type fields \
+		 * minus the string 0-termination \
+		 */ \
+		sizeof(str) + 3 - 1, \
+		USB_DT_WEBUSB_URL, \
+		USB_URL_SCHEME_##scheme, \
+		str \
+	}
+
 /* Setup Packet */
 struct usb_setup_packet {
 	uint8_t  bmRequestType;
@@ -290,5 +337,6 @@ extern const uint8_t usb_string_desc[];
 /* USB string descriptor with the firmware version */
 extern const void * const usb_fw_version;
 extern const struct bos_context bos_ctx;
+extern const void *webusb_url;
 
 #endif /* __CROS_EC_USB_DESCRIPTOR_H */