I have a device whose video-out is HDMI. My laptop has an HDMI port. My laptop is running Linux.
Can I view the device's video-out on my laptop? How?
Yes you can. However you will need to buy a device known as a frame grabber. One of its input connectors needs to be HDMI (The HDMI connector on your laptop is only used for output).
To repeat: Yes you can with extra hardware.