On Mon, Aug 5, 2013 at 3:22 PM, Jiri Kosina <jkosina@xxxxxxx> wrote: > On Fri, 2 Aug 2013, Benjamin Tissoires wrote: > >> > Could you please elaborate? (and put an elaborate description to revert >> > commit log perhaps?) >> >> Sure, so here is the revert commit log: >> >> -- >> >> Commit "HID: hid-logitech-dj, querying_devices was never set" activate >> a flag which guarantees that we do not ask the receiver for too many >> enumeration. When the flag is set, each following enumeration call is >> discarded (the usb request is not forwarded to the receiver). The flag >> is then released when the driver receive a pairing information event, >> which normally follows the enumeration request. >> However, the USB3 bug makes the driver think the enumeration request >> has been forwarded to the receiver. However, it is actually not the >> case because the USB stack returns -EPIPE. So, when a new unknown >> device appears, the workaround consisting in asking for a new >> enumeration is not working anymore: this new enumeration is discarded >> because of the flag, which is never reset. >> >> A solution could be to trigger a timeout before releasing it, but for >> now, let's just revert the patch. >> >> -- > > Thanks Benjamin. > > I'd like to have a bit more clarification about the USB3 bug, as this > whole issue is not completely clear to me. > > To be more specific -- when exactly do we receive -EPIPE, why do we > receive it and why do we not handle it properly? Sure, I'll try (though the more I think of it, the more it seems blurry to me :( ). So the initial probe function in hid-logitech-dj was implemented by using a direct call to hid_output_raw_report(). This call was synchronous, so we did get the -EPIPE return code. Then, the probe() function returns the -EPIPE error, cleaning the receiver and unregister it from the hid bus. However, now, we use hid_hw_request(), which is asynchronous (from what I can read). At least, this code returns "void" as the set_report command seems to be scheduled for later handling. In usbhid, when the queue is flushed, I did not found a way to retrieve the error code... So basically, the -EPIPE is received in usbhid_restart_ctrl_queue(), but nothing notifies hid-logitech-dj from the error. In the end, the probe() function returns without error code, but the receiver never received the notification. Cheers, Benjamin -- To unsubscribe from this list: send the line "unsubscribe linux-input" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
