HDCP Content Type Interface

Ramalingam C ramalingam.c at intel.com
Thu Sep 12 07:47:51 UTC 2019

On 2019-09-09 at 15:54:50 +0000, Lakha, Bhawanpreet wrote:
> Hi all,
> This is regarding the recent hdcp content type patch that was merged into drm-misc. (https://patchwork.freedesktop.org/patch/320958/?series=57233&rev=11)
> There are displays on the market that advertise HDCP 2.2 support and will pass authentication and encryption but will then show a corrupted/blue/black screen (the driver cannot detect this). These displays work with HDCP 1.4 without any issues. Due to the large number of HDCP-supporting devices on the market we might not be able to catch them with a blacklist.
> From the user modes perspective, HDCP1.4 and HDCP2.2 Type0 are the same thing. Meaning that this interface doesn't allow us to force the hdcp version. Due to the problems mentioned above we might want to expose the ability for a user to force an HDCP downgrade to a certain level (e.g. 1.4) in case they experience problems.
> What are your thoughts? and what would be a good way to deal with it?

As you mentioned, uAPI is designed to be HDCP version agnostic. Kernel
supposed to exercise the highest version of HDCP supported on panel and

As we implement the HDCP spec support, if a device is non-compliant with
HDCP spec after completing the HDCP authentication, I dont think we need
to worry about it.

In case if you want to track and implement a quirk for it, like not to
project the HDCP2.2 capability, you can use the receiver id of that panel
to track it.

> Thanks,
> Bhawan

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