usb: gadget: add WebUSB landing page support

There is a custom (non-USB IF) extension to the USB standard:

https://wicg.github.io/webusb/

This specification is published under the W3C Community Contributor
Agreement, which in particular allows to implement the specification
without any royalties.

The specification allows USB gadgets to announce an URL to landing
page and describes a Javascript interface for websites to interact
with the USB gadget, if the user allows it. It is currently
supported by Chromium-based browsers, such as Chrome, Edge and
Opera on all major operating systems including Linux.

This patch adds optional support for Linux-based USB gadgets
wishing to expose such a landing page.

During device enumeration, a host recognizes that the announced
USB version is at least 2.01, which means, that there are BOS
descriptors available. The device than announces WebUSB support
using a platform device capability. This includes a vendor code
under which the landing page URL can be retrieved using a
vendor-specific request.

Previously, the BOS descriptors would unconditionally include an
LPM related descriptor, as BOS descriptors were only ever sent
when the device was LPM capable. As this is no longer the case,
this patch puts this descriptor behind a lpm_capable condition.

Usage is modeled after os_desc descriptors:
echo 1 > webusb/use
echo "https://www.kernel.org" > webusb/landingPage

lsusb will report the device with the following lines:
  Platform Device Capability:
    bLength                24
    bDescriptorType        16
    bDevCapabilityType      5
    bReserved               0
    PlatformCapabilityUUID    {3408b638-09a9-47a0-8bfd-a0768815b665}
      WebUSB:
        bcdVersion    1.00
        bVendorCode      0
        iLandingPage     1 https://www.kernel.org

Signed-off-by: Jó Ágila Bitsch <jgilab@gmail.com>
Link: https://lore.kernel.org/r/Y8Crf8P2qAWuuk/F@jo-einhundert
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 92 insertions, 10 deletions

diff --git a/drivers/usb/gadget/composite.c b/drivers/usb/gadget/composite.c
index 403563c06477..8e2603688016 100644
--- a/drivers/usb/gadget/composite.c
+++ b/drivers/usb/gadget/composite.c
@@ -14,9 +14,11 @@
 #include <linux/device.h>
 #include <linux/utsname.h>
 #include <linux/bitfield.h>
+#include <linux/uuid.h>
 
 #include <linux/usb/composite.h>
 #include <linux/usb/otg.h>
+#include <linux/usb/webusb.h>
 #include <asm/unaligned.h>
 
 #include "u_os_desc.h"
@@ -713,14 +715,16 @@ static int bos_desc(struct usb_composite_dev *cdev)
 	 * A SuperSpeed device shall include the USB2.0 extension descriptor
 	 * and shall support LPM when operating in USB2.0 HS mode.
 	 */
-	usb_ext = cdev->req->buf + le16_to_cpu(bos->wTotalLength);
-	bos->bNumDeviceCaps++;
-	le16_add_cpu(&bos->wTotalLength, USB_DT_USB_EXT_CAP_SIZE);
-	usb_ext->bLength = USB_DT_USB_EXT_CAP_SIZE;
-	usb_ext->bDescriptorType = USB_DT_DEVICE_CAPABILITY;
-	usb_ext->bDevCapabilityType = USB_CAP_TYPE_EXT;
-	usb_ext->bmAttributes = cpu_to_le32(USB_LPM_SUPPORT |
-					    USB_BESL_SUPPORT | besl);
+	if (cdev->gadget->lpm_capable) {
+		usb_ext = cdev->req->buf + le16_to_cpu(bos->wTotalLength);
+		bos->bNumDeviceCaps++;
+		le16_add_cpu(&bos->wTotalLength, USB_DT_USB_EXT_CAP_SIZE);
+		usb_ext->bLength = USB_DT_USB_EXT_CAP_SIZE;
+		usb_ext->bDescriptorType = USB_DT_DEVICE_CAPABILITY;
+		usb_ext->bDevCapabilityType = USB_CAP_TYPE_EXT;
+		usb_ext->bmAttributes = cpu_to_le32(USB_LPM_SUPPORT |
+							USB_BESL_SUPPORT | besl);
+	}
 
 	/*
 	 * The Superspeed USB Capability descriptor shall be implemented by all
@@ -821,6 +825,37 @@ static int bos_desc(struct usb_composite_dev *cdev)
 		}
 	}
 
+	/* The WebUSB Platform Capability descriptor */
+	if (cdev->use_webusb) {
+		struct usb_plat_dev_cap_descriptor *webusb_cap;
+		struct usb_webusb_cap_data *webusb_cap_data;
+		uuid_t webusb_uuid = WEBUSB_UUID;
+
+		webusb_cap = cdev->req->buf + le16_to_cpu(bos->wTotalLength);
+		webusb_cap_data = (struct usb_webusb_cap_data *) webusb_cap->CapabilityData;
+		bos->bNumDeviceCaps++;
+		le16_add_cpu(&bos->wTotalLength,
+			USB_DT_USB_PLAT_DEV_CAP_SIZE(USB_WEBUSB_CAP_DATA_SIZE));
+
+		webusb_cap->bLength = USB_DT_USB_PLAT_DEV_CAP_SIZE(USB_WEBUSB_CAP_DATA_SIZE);
+		webusb_cap->bDescriptorType = USB_DT_DEVICE_CAPABILITY;
+		webusb_cap->bDevCapabilityType = USB_PLAT_DEV_CAP_TYPE;
+		webusb_cap->bReserved = 0;
+		export_uuid(webusb_cap->UUID, &webusb_uuid);
+
+		if (cdev->bcd_webusb_version != 0)
+			webusb_cap_data->bcdVersion = cpu_to_le16(cdev->bcd_webusb_version);
+		else
+			webusb_cap_data->bcdVersion = WEBUSB_VERSION_1_00;
+
+		webusb_cap_data->bVendorCode = cdev->b_webusb_vendor_code;
+
+		if (strnlen(cdev->landing_page, sizeof(cdev->landing_page)) > 0)
+			webusb_cap_data->iLandingPage = WEBUSB_LANDING_PAGE_PRESENT;
+		else
+			webusb_cap_data->iLandingPage = WEBUSB_LANDING_PAGE_NOT_PRESENT;
+	}
+
 	return le16_to_cpu(bos->wTotalLength);
 }
 
@@ -1744,7 +1779,7 @@ composite_setup(struct usb_gadget *gadget, const struct usb_ctrlrequest *ctrl)
 					cdev->desc.bcdUSB = cpu_to_le16(0x0210);
 				}
 			} else {
-				if (gadget->lpm_capable)
+				if (gadget->lpm_capable || cdev->use_webusb)
 					cdev->desc.bcdUSB = cpu_to_le16(0x0201);
 				else
 					cdev->desc.bcdUSB = cpu_to_le16(0x0200);
@@ -1779,7 +1814,7 @@ composite_setup(struct usb_gadget *gadget, const struct usb_ctrlrequest *ctrl)
 			break;
 		case USB_DT_BOS:
 			if (gadget_is_superspeed(gadget) ||
-			    gadget->lpm_capable) {
+			    gadget->lpm_capable || cdev->use_webusb) {
 				value = bos_desc(cdev);
 				value = min(w_length, (u16) value);
 			}
@@ -2013,6 +2048,53 @@ unknown:
 			goto check_value;
 		}
 
+		/*
+		 * WebUSB URL descriptor handling, following:
+		 * https://wicg.github.io/webusb/#device-requests
+		 */
+		if (cdev->use_webusb &&
+		    ctrl->bRequestType == (USB_DIR_IN | USB_TYPE_VENDOR) &&
+		    w_index == WEBUSB_GET_URL &&
+		    w_value == WEBUSB_LANDING_PAGE_PRESENT &&
+		    ctrl->bRequest == cdev->b_webusb_vendor_code) {
+			unsigned int	landing_page_length;
+			unsigned int	landing_page_offset;
+			struct webusb_url_descriptor *url_descriptor =
+					(struct webusb_url_descriptor *)cdev->req->buf;
+
+			url_descriptor->bDescriptorType = WEBUSB_URL_DESCRIPTOR_TYPE;
+
+			if (strncasecmp(cdev->landing_page, "https://",  8) == 0) {
+				landing_page_offset = 8;
+				url_descriptor->bScheme = WEBUSB_URL_SCHEME_HTTPS;
+			} else if (strncasecmp(cdev->landing_page, "http://", 7) == 0) {
+				landing_page_offset = 7;
+				url_descriptor->bScheme = WEBUSB_URL_SCHEME_HTTP;
+			} else {
+				landing_page_offset = 0;
+				url_descriptor->bScheme = WEBUSB_URL_SCHEME_NONE;
+			}
+
+			landing_page_length = strnlen(cdev->landing_page,
+				sizeof(url_descriptor->URL)
+				- WEBUSB_URL_DESCRIPTOR_HEADER_LENGTH + landing_page_offset);
+
+			if (ctrl->wLength < WEBUSB_URL_DESCRIPTOR_HEADER_LENGTH
+					    + landing_page_length)
+				landing_page_length = ctrl->wLength
+					- WEBUSB_URL_DESCRIPTOR_HEADER_LENGTH + landing_page_offset;
+
+			memcpy(url_descriptor->URL,
+				cdev->landing_page + landing_page_offset,
+				landing_page_length - landing_page_offset);
+			url_descriptor->bLength = landing_page_length
+				- landing_page_offset + WEBUSB_URL_DESCRIPTOR_HEADER_LENGTH;
+
+			value = url_descriptor->bLength;
+
+			goto check_value;
+		}
+
 		VDBG(cdev,
 			"non-core control req%02x.%02x v%04x i%04x l%d\n",
 			ctrl->bRequestType, ctrl->bRequest,