Support for my mouse in nusb/kb

[petermikkelsen10@gmail.com]

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Hello,

I have recently installed 9front on my laptop and only some USB mice seems to work.
After a bit of investigation it turned out to be a problem with the devices which also presented part of them as a keyboard,
so I looked a bit at the USB hid spec. It seems that some things that nusb/kb does (like setting the idle time) is not
always supported by all devices, so this patch changes those things. It fixes the problem for me and now I can use my
new mouse :)

Sysinfo is attached.

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from postmaster@plan9:
The following attachment had content that we can't
prove to be harmless.  To avoid possible automatic
execution, we changed the content headers.
The original header was:

	Content-Disposition: attachment; filename=usb.patch
	Content-Type: text/plain; charset="US-ASCII"
	Content-Transfer-Encoding: 7bit

[-- Attachment #2.2: usb.patch.suspect --]
[-- Type: application/octet-stream, Size: 1221 bytes --]

diff -r 22dd54063d2c sys/src/cmd/nusb/kb/kb.c
--- a/sys/src/cmd/nusb/kb/kb.c	Sat Apr 11 18:09:48 2020 +0200
+++ b/sys/src/cmd/nusb/kb/kb.c	Sun Apr 12 04:35:20 2020 +0200
@@ -330,12 +330,21 @@
 
 	iface = f->dev->usb->ep[eid]->iface;
 
-	/*
-	 * DWC OTG controller misses some split transaction inputs.
-	 * Set nonzero idle time to return more frequent reports
-	 * of keyboard state, to avoid losing key up/down events.
+	/* Appendix G of the USB Hid spec says that only boot mouse and boot keyboards 
+	 * are required to support setting the protocol, so only try it for those.
 	 */
-	usbcmd(f->dev, Rh2d|Rclass|Riface, Setidle, 8<<8, iface->id, nil, 0);
+	if (iface->csp != KbdCSP && iface->csp != PtrCSP)
+		return 0;
+
+	/* Only set the idle time keyboards since only those are required to support it */
+	if (iface->csp == KbdCSP) {
+		/*
+		 * DWC OTG controller misses some split transaction inputs.
+		 * Set nonzero idle time to return more frequent reports
+		 * of keyboard state, to avoid losing key up/down events.
+		 */
+		usbcmd(f->dev, Rh2d|Rclass|Riface, Setidle, 8<<8, iface->id, nil, 0);
+	}
 
 	f->nrep = usbcmd(f->dev, Rd2h|Rstd|Riface, Rgetdesc, Dreport<<8, iface->id,
 		f->rep, sizeof(f->rep));