On Fri, Dec 23, 2022 at 12:58:41PM +0000, Dmitrii Pasechnik wrote: > On Thu, Dec 22, 2022 at 04:24:55PM -0500, Alan Stern wrote: > > A bit off to the side from the main point of this thread, but... > > > > On Thu, Dec 22, 2022 at 10:32:09AM +0000, Dima Pasechnik wrote: > > > > > > > > > On 20 December 2022 19:57:05 WET, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote: > > > >> USB Interfaces: MSD, CDC, HID, WebUSB > > > > > > > >Which agrees with the information on the web site. I have no idea what > > > >WebUSB is supposed to be. > > > > > > WebUSB is a JavaScript API, supported by Chromium -derived browsers (Firefox not there yet) > > > > > > https://en.wikipedia.org/wiki/WebUSB > > > > The Wikipedia article agrees with you that WebUSB is a JavaScript API. > > As such, it is used for communication between web browsers and > > JavaScript programs. > > No, it's used by browsers (which run JavaScript code in them) to > communicate with USB hardware. Or, if you like, > standalone JavaScript programs to communicate with USB hardware. > Let me copy from the wiki here: > > --------------------------------- > A Universal Serial Bus, or a USB is an industry standard [...] > WebUSB is a set of API calls that enable access to these hardware > devices from web pages. WebUSB is developed by the World Wide Web > Consortium(W3C).[1] The webUSB API provides a safe, and developer > familiar means of communication to edges devices from web pages. The > webUSB API integrates into existing USB libraries and shortens the > development cycle for integrating new devices into the web environment > by not needing to wait for browser support for these devices. > > Early versions of webUSB came out around as an alternative to Flash, > Chrome Serial, and other custom approaches to connecting browsers to > hardware. WebUSB aims to solve the four goals of any interface being; > fast to make, cross platform, look good, accessibility. > > > Not for communication between programs and USB > > devices. So I don't understand why a USB device needs to be concerned > > about it. > > I hope the above explains. Actually, it's ambiguous. The article says that WebUSB is an API used by JavaScript programs when they want to interact with a USB device. Which means it is something that JavaScript programs can know about and interact with. Fine. But the article doesn't say what happens on the device's side of the conversation. Does the WebUSB framework use some special messages when communicating with a USB device, so it will only work with devices which support WebUSB's protocol, or does it use plain ordinary USB messages which any USB device will support? To put it another way, do USB devices need to have specialized firmware in order to be compatible with WebUSB, or will WebUSB work with all USB devices? If the latter is true then why does the BBC micro:bit device have a special WebUSB interface? Does the extra interface provide some sort of device-specific information which WebUSB can make use of but which isn't essential? Alan Stern
