Re: [PATCH 1/1] Add virtio-input driver.

  Hi,

quoted

+static int virtinput_send_status(struct virtio_input *vi,
+                                u16 type, u16 code, s32 value)
+{
+       struct virtio_input_event *stsbuf;
+       struct scatterlist sg[1];
+
+       stsbuf = kzalloc(sizeof(*stsbuf), GFP_ATOMIC);
+       if (!stsbuf)
+               return -ENOMEM;
+
+       stsbuf->type  = cpu_to_le16(type);
+       stsbuf->code  = cpu_to_le16(code);
+       stsbuf->value = cpu_to_le32(value);
+       sg_init_one(sg, stsbuf, sizeof(*stsbuf));
+       virtqueue_add_outbuf(vi->sts, sg, 1, stsbuf, GFP_ATOMIC);
+       virtqueue_kick(vi->sts);

GFP_ATOMIC, eww. But everyone does that for input_event() callbacks..

Yea, did it this way because I saw it elsewhere.

we should fix that for user-space input one day.

Sounds like I have to use GFP_ATOMIC and can't switch to GFP_KERNEL,
correct?

quoted

+       size = virtinput_cfg_select(vi, VIRTIO_INPUT_CFG_ABS_INFO, abs);
+       virtio_cread(vi->vdev, struct virtio_input_config, u.abs.min, &mi);
+       virtio_cread(vi->vdev, struct virtio_input_config, u.abs.max, &ma);
+       virtio_cread(vi->vdev, struct virtio_input_config, u.abs.fuzz, &fu);
+       virtio_cread(vi->vdev, struct virtio_input_config, u.abs.flat, &fl);

abs.resolution is missing. Please add it, we really also need to add
it to uinput one day.

Ok.  How should I handle cases where the resolution is either not known
or not fixed?  Just leave it zero?

quoted

+       vi->idev->name = vi->name;
+       vi->idev->phys = vi->phys;

Can you set vi->idev->uniq to the virtio-bus path?

quoted

+       vi->idev->id.bustype = BUS_VIRTUAL;
+       vi->idev->id.vendor  = 0x0001;
+       vi->idev->id.product = 0x0001;
+       vi->idev->id.version = 0x0100;

Please don't hardcode those. All user-space based interaction with
input-devices relies on those IDs. Can we retrieve it from the host
just like the name?

Yes, we can.

There will be emulated devices, i.e. the input coming from
vnc/gtk/whatever will be sent to the virtio devices (instead of ps/2 or
usb).  For these we should probably have fixed IDs per device.  There
are keyboard/mouse/tablet at the moment.  Suggestions how to pick IDs?

There will also be pass-through support, i.e. qemu
opening /dev/input/event<nr> and forwarding everything to the guest.
How should that be handled best?  Copy all four from the host?  Even
though the bustype is BUS_USB?  Not sure this actually improves things
because the guest can match the device, or whenever this confuses apps
due to BUS_USB being applied to virtio devices ...

cheers,
  Gerd