Failed to send the report only during hot-plugged event, Duplicate of issue #65

[JunzheFan]

I have been tested my device which is a headset connector with WebHID for a few days, I encountered a strange behaviour where I can not send the report using the device object received on the hot-plugged event, it throwed a DOMException with permisson not allowed. I tried a few workaround and found that if I set a 3 seconds delay then acquired the device, the output report can be successfully sent to device. Could it be the device is not actually ready for operation when the connect event fired like a race condition for re-granting permisson ? I assume the WebHID internally maintained a list of granted device, so the device object received on the connect callback argument is essentially the same object as the result returned from the navigator.hid.getDevices(), but it's strange I need to set a delay to get the device before can start doing operation, Below is code i used to showcase the situations mentioned above, thanks in advance

    navigator.hid.addEventListener("connect", async ({ device }) => {
      // Case 1
      // Failed to write the report, immediately send
      // if (!device.opened) {
      //   await device.open();
      // }
      // const data = new Uint8Array([0x6, 0x1, 0x0, 0, 0, 0, 0, 0]);
      // device.sendReport(data[0], data.slice(1, data.length));

      // Case 2 
      // Failed to write the report, send after a few seconds
      // if (!device.opened) {
      //   await device.open();
      // }
      // setTimeout(() => {
      //   const data = new Uint8Array([0x6, 0x1, 0x0, 0, 0, 0, 0, 0]);
      //   device.sendReport(data[0], data.slice(1, data.length));
      // }, 3000);
      
      // Case 3
      // if set a 2-3 seconds delay, then get the device, the report can be successfully sent 
      setTimeout(async () => {
        let [Device] = await navigator.hid.getDevices();
        if (!Device.opened) {
          await Device.open();
        }
        const data = new Uint8Array([0x6, 0x1, 0x0, 0, 0, 0, 0, 0]);
        Device.sendReport(data[0], data.slice(1, data.length));
      }, 3000);
    });

[nondebug]

Is anything logged in chrome://device-log or the developer console?

I agree this is strange. I don't think this is an implementation bug, this seems like a device error. If it were related to Chrome's permission model then it should have failed to open the device, but based on your description it sounds like open succeeded but sendReport failed.

[JunzheFan]

yes you are correct, the device can be successfully opened , I went to the chrome://device-log and got the following error message, and thanks to the error log I think I found where the problem was, my device has three top-level Application collections, during the hot-plugged event I found that WebHID only enumerated one of the collections which does not have the output descriptor set (I logged the device object received on the callback parameter using console.log(JSON.stringify(device.collections)); ) , it seems the other two collections which do have the output descriptor are missing and it's sub-device I am sending the report to. That do explain why I set a few seconds delay and acquire my device again can send the report successfully because in this case all three top-level Application collections are enumerated. But I am still not sure if the WebHID is triggering this event too soon ?

[JunzheFan]

@nondebug HI matt, I found that my problem is essentially a duplicate of this issue reported two years ago, #65, since on Windows it seems not possible to wait for all topl level collections to be enumerated before firing the connect event, is there any update on the implementation of the 'devicechange' event you mentioned as sort of workaround in the issue