@amosbatto DisplayPort alt-mode is in fact how most USB-C to HDMI adapters work. HDMI alt-mode, although it exists, is rather rare and not supported that well across various hardware.
@dos, OK, that makes sense, but if DisplayPort Alt Mode is carrying an HDMI signal, we still have the same question for RYF certification.
Does the DCSS driver for the iMX8MQ no longer require the HDMI DRM blob or is the video being converted to HDMI outside the iMX8MQ?
@amosbatto DisplayPort alt-mode is carrying a DisplayPort signal, not HDMI. It's usually the adapter that converts it to HDMI.
@dos, Oh I assumed that DP alt-mode was like normal DP, but I Googled it and found that there is no DP Dual Mode (DP++) over DP alt-mode, so it isn't possible to send an HDMI signal over DP alt-mode. We will need an active adapter to convert from DP to HDMI.
This article explains it:
@amosbatto Yes, I know, and I said that earlier - most USB-C to HDMI adapters use DP alt-mode, which is universally supported, and not HDMI alt-mode, which is rather rare and can't be used together with USB signal at the same time.
@dos, HDMI alt-mode not being common gives me hope for the future. As more devices move to USB-C, we can get rid of HDMI, which requires licensing fees, and just use DisplayPort, which is a freer standard. Nice to find something positive in this dreary world.