SuperHID v2

Downsides of SuperHID v1

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Here's a picture that compares the two designs:

Image Added

SuperHID v1

Introduction

Some HID background could be useful to understand the core of SuperHID.

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• No code needed in the guest VM
• Multi-touch works in Microsoft Windows 8, and any other pv-usb-enabled guest
• All the input still goes through input_server, which gives total control over what event goes to which VM

Downsides

• The input events follow a long path, as illustrated above

To do

• Implement the plugin directly in input_server, to reduce the packets journey.
• Implement a way to skip the relative-to-absolute translation that happens in input_server, to make input faster and more reliable (but potentially breaking other input features).
• Enhance the superhid gadget driver (and/or the virtual USB controller) to be able to create multiple devices (right now we get only one).
• Get the toolstack and the USB subsystem to automatically pass the right SuperHID fake input device to the right guest.

The USB controller

The superhid proof-of-concept is now functionnal, and the superhid device itself can be used as-is.

However, the USB controller needs a lot of work. Right now, we use dummy_hcd, which simulates a real life controller, with power, latency and ports limitations. This module has been created only for development purposes, to simulate devices before actually getting access to the real hardware. The problem of that module is that is requires the clock to be set to 1000HZ, and it probably uses too much resources.

What SuperHID needs is something that would be more of a "fake USB controller", that would be dummy-er than dummy_hcd. Like just enough code to create a fake controller and pipe the packets to the fake devices (gadgets).

How to build and use SuperHID

• Make sure the dom0 Linux kernel has been (re)compiled with an HZ value of 1000 and gadget support.
• In OE: ./bb xenclient-superhid
• Send and install the resulting module to the (OpenXT) test machine (superhid.ko)
• In input.git/superhid (with a 32 bits compiler): gcc -o shp -lpthread -levent superhidplugin.c
• Send shp to the test machine

• On the test machine:

  # cat > /etc/modprobe.d/superhid.conf <<EOF
  options superhid idVendor=0x03eb idProduct=0x211c bcdDevice=0x0001 iManufacturer=jed iProduct=superhid
  EOF
  # modprobe dummy_hcd
  # modprobe superhid
  # ./shp <domid>
  

Note: idVendor and idProduct are set to an existing input device to make some guests recognise it. Ideally, those values could be anything, as the device is just a standard HID device.

• Pass the superhid device to the (Windows/Linux) guest

At that point, the guest should see a new multitouch HID device and should be able to use it.