linux-kernel - RE: [PATCH] drm/hyperv: Fix double mouse pointers

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Message-ID: <BYAPR21MB1270C4427C264D14F151A0CCBFDB9@BYAPR21MB1270.namprd21.prod.outlook.com>
Date:   Wed, 15 Sep 2021 06:59:18 +0000
From:   Dexuan Cui <decui@...rosoft.com>
To:     Deepak Rawat <drawat.floss@...il.com>
CC:     Haiyang Zhang <haiyangz@...rosoft.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] drm/hyperv: Fix double mouse pointers

> From: Deepak Rawat <drawat.floss@...il.com>
> Sent: Tuesday, September 14, 2021 8:59 AM
> ...
> > +/* Send mouse pointer info to host */
> > +int hyperv_send_ptr(struct hv_device *hdev)
> > +{
> > +       struct synthvid_msg msg;
> > +
> > +       memset(&msg, 0, sizeof(struct synthvid_msg));
> > +       msg.vid_hdr.type = SYNTHVID_POINTER_POSITION;
> > +       msg.vid_hdr.size = sizeof(struct synthvid_msg_hdr) +
> > +               sizeof(struct synthvid_pointer_position);
> > +       msg.ptr_pos.is_visible = 1;
> 
> "is_visible" should be 0 since you want to hide the pointer. Maybe
> better, accept these from the caller.

According to my test, "is_visible = 0" doesn't work, i.e. can't hide the
unwanted HW mouse poiner. It looks like the field is for some very old
legacy Windows VMs like Windows Vista.

Haiyang also replied in another email, saying "is_visible = 0" doesn't
work.

> > +       msg.ptr_pos.video_output = 0;
> > +       msg.ptr_pos.image_x = 0;
> > +       msg.ptr_pos.image_y = 0;
> > +       hyperv_sendpacket(hdev, &msg);
> > +
> > +       memset(&msg, 0, sizeof(struct synthvid_msg));
> > +       msg.vid_hdr.type = SYNTHVID_POINTER_SHAPE;
> > +       msg.vid_hdr.size = sizeof(struct synthvid_msg_hdr) +
> > +               sizeof(struct synthvid_pointer_shape);
> > +       msg.ptr_shape.part_idx = SYNTHVID_CURSOR_COMPLETE;
> > +       msg.ptr_shape.is_argb = 1;
> > +       msg.ptr_shape.width = 1;
> > +       msg.ptr_shape.height = 1;
> > +       msg.ptr_shape.hot_x = 0;
> > +       msg.ptr_shape.hot_y = 0;
> > +       msg.ptr_shape.data[0] = 0;
> > +       msg.ptr_shape.data[1] = 1;
> > +       msg.ptr_shape.data[2] = 1;
> > +       msg.ptr_shape.data[3] = 1;
> > +       hyperv_sendpacket(hdev, &msg);
> > +
> 
> Is it necessary to send SYNTHVID_POINTER_SHAPE here? Perhaps we should

According to my test, yes. If I don't send a SYNTHVID_POINTER_SHAPE message,
the unwanted mouse pointer can't be hidden. As we know, the protocol between
the VSC and the VSP is not well documented to us. I can ask Hyper-V
team for some clarification on this, but it's probably we can just use the current
version of hiding the mouse pointer as-is -- this has been used for 10+ years
in the hyperv_fb driver without any issue. :-)

> separate SYNTHVID_POINTER_POSITION and SYNTHVID_POINTER_SHAPE into
> different functions.

Since the 2 messages are only used here, I suggest we keep it as-is.

Thanks,
-- Dexuan