HDCP Content Type Interface
hwentlan at amd.com
Thu Sep 12 19:21:28 UTC 2019
On 2019-09-12 10:57 a.m., Jani Nikula wrote:
> On Thu, 12 Sep 2019, Harry Wentland <hwentlan at amd.com> wrote:
>> On 2019-09-12 3:47 a.m., Ramalingam C wrote:
>>> 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.
>> Tell that to our (or your) customers.
> Agreed, let's rather not.
>> In this case an enduser might plug in a bad monitor or TV and be unable
>> to play protected content.
>> What if we add a new enum value to the content_type property that says
> In general, I think if the fix is to teach the user to jump through
> hoops in case the output is not working, it is really not a fix.
> Would, say, a set top box or a Blu-ray player have a setting to force
> HDCP 1.4, and a troubleshooting item in the manual to select that if the
> display does not work? Or would OS X have that?
Not sure. AFAIU on other OS we're currently dealing with this through
monitor quirks. We can probably pull the same quirks to DRM.
> If broken HDCP 2.2 sink support is a widespread problem (is it?), what
> do other HDCP sources do? If it's a Linux issue, what are we doing wrong
> or different?
Not a Linux issue and not overly widespread. Looks like a handful of
receivers are problematic.
>>> 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.
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