Add mechanism to reset device just before attaching

Some device require reset after interacting with previous driver. When
device was used with usbip-host before, it took care of that when
detaching from previous target (VM). But if it was attached to some
other driver in sys-usb before, this needs to be done manually.

To limit possible impact, make this opt-in. There are two methods to opt
into this feature:
1. Enable it for all devices using (adjust sys-usb name if applicable):
   qvm-service --enable sys-usb usb-reset-on-attach
2. Enable for specific device by setting QUBES_USB_RESET udev property.

QubesOS/qubes-issues#8953

rpm_spec/qubes-usb-proxy.spec.in

@@ -31,6 +31,7 @@ make install-vm DESTDIR=${RPM_BUILD_ROOT}
 /usr/lib/qubes/usb-import
 /usr/lib/qubes/usb-export
 /usr/lib/qubes/usb-detach-all
+/usr/lib/qubes/usb-reset
 
 %changelog
 @CHANGELOG@

src/usb-export

@@ -108,6 +108,16 @@ fi
 printf 'add %s' "$busid" > "$SYS_USBIP_HOST/match_busid" || exit 1
 if [ -n "$attach_to_usbip" ]; then
     echo "$busid" > "$SYS_USBIP_HOST/bind" || exit 1
+
+    # optionally reset the device to clear any state from previous driver
+    reset_on_attach=$(udevadm info --query=property \
+        --value --property=QUBES_USB_RESET --path="$devpath")
+    if [ -f /run/qubes-service/usb-reset-on-attach ]; then
+        reset_on_attach=1
+    fi
+    if [ -n "$reset_on_attach" ]; then
+        /usr/lib/qubes/usb-reset "$devpath"
+    fi
 fi
 
 # One more safety check - make sure the device is available

src/usb-reset

@@ -0,0 +1,25 @@
+#!/usr/bin/python3
+
+import sys
+import os
+import fcntl
+from pathlib import Path
+
+# from /usr/include/linux/usbdevice_fs.h
+# _IO('U', 20)
+USBDEVFS_RESET = 0x5514
+
+def main():
+    if len(sys.argv) != 2:
+        print("Usage: usb-reset sysfs-devpath", file=sys.stderr())
+        exit(2)
+    devpath = sys.argv[1]
+    uevent = (Path(devpath) / "uevent").read_text()
+    devname = [line.partition("=")[2]
+               for line in uevent.splitlines()
+               if line.startswith("DEVNAME=")][0]
+    with (Path("/dev") / devname).open("w") as dev_f:
+        fcntl.ioctl(dev_f, USBDEVFS_RESET, 0)
+
+if __name__ == "__main__":
+    main()