Re: [RFC v1 01/20] drm/hdcp: HDCP bitmask property for connectors

[Ramalingam C <ramalingam.c@intel.com>]

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On Thursday 13 July 2017 04:06 PM, Daniel Vetter wrote:
> On Thu, Jul 13, 2017 at 12:15 PM, Ramalingam C <ramalingam.c@intel.com> wrote:
>>
>> On Thursday 13 July 2017 02:15 PM, Daniel Vetter wrote:
>>
>> On Thu, Jul 13, 2017 at 8:54 AM, Ramalingam C <ramalingam.c@intel.com>
>> wrote:
>>
>> On Thursday 13 July 2017 11:39 AM, Daniel Vetter wrote:
>>
>> On Wed, Jul 12, 2017 at 9:10 PM, Sean Paul <seanpaul@chromium.org> wrote:
>>
>> Why all these intermediate steps and different failure modes? Either hdcp
>> works, or it doesnt (and we can split up with the type 0 or type 1 if
>> needed), but I don't know what userspace would do with all the other
>> stuff?
>>
>> enum values  HDCP_ENABLE, HDCP_ENABLE_TYPE1 and HDCP_DISABLE along with
>> kobj-uevent
>> for HDCP state change, could do the bare minimal HDCP1.4 and HDCP2.2
>> configuration.
>>
>> And without Type info it is not possible for HDCP2.2.
>>
>> I've had requests from chrome team to expose HDCP version, so I don't think
>> this
>> is too contentious.
>>
>> I think it'd still be easier if we start out with the current content
>> protection props that CrOS is using, and then figure out how to layer
>> the exact version/standard on top? One thing at a time and all that.
>> -Daniel
>>
>> I understand the approach.
>>
>> But Only problem is current upstreaming effort is for HDCP2.2 support at DRM
>> with a design which can
>> easily accommodate other versions too. So we  need to stretch current CrOS
>> property a bit with
>> ENABLE_TYPE1 and UNSUPPORTED etc. Hope that should be fine for all.
>>
>> Yeah, but if we just go with enable (without specifying the type) we
>> could still enable the highest hdcp level (so 2.2 for our case). At
>> least I don't see a reason why we need to already have the
>> enable_type1 thing. Can you pls explain why you think this is
>> necessary?
>>
>> There seems to be a need to force type1, but I think it's easier to do
>> that as an extension. Of course we need to keep it in mind meanwhile.
>>
>> Background for this need of Type info in HDCP2.2 implementation is as
>> follows:
> Aside: You're quoting is broken for inline quoting. Either fix the
> quoting or top-quote (there's no difference between your text and
> mine, mine should be indented with > or | or similar).
Sorry for the inconvenience. Hope now it is fine. Just reset the 
settings on thunderbird
>
>> HDCP2.2 Spec classify the protected content as Type 0 and Type 1. For
>> Example lets say
>> - A HDCP2.2 Src is connected to HDCP repeater
>> - that repeater is connected to a HDCP2.2 panel
>> - that same repeater is also connected to a HDCP1.4 panel.
>>
>> In this topology, as part of Repeater authentication:
>> - HDCP2.2 Source will mention the Content Type to HDCP2.2 Repeater
>> - Repeater can transmit this Type 1 content to HDCP2.2 compliant sink only
>> (which is HDCP 2.2 panel here).
>> - Repeater can transmit any type0 content to any other devices (like HDCP1.4
>> panel here).
>> - Device with no HDCP support will get Neither of Type 0 or Type 1.
>>
>> So if we implement HDCP2.2 with HDCP_ENABLE state alone there is no way for
>> Userspace
>> to request for HDCP2.2 protection only. In this case we wont know the
>> content type classification.
> Yes, that is the case, but also the point of gradual enabling. Atm
> (with the current CrOS usersapce) userspace can ask for "pls give me
> content protection, I don't care what level/type". That itself is
> already useful, and a good step forward. Allowing to ask for a
> specific type is something on top.
Ok. When i think over it, that sounds as a  good idea to go gradually 
for enabling HDCP2.2.
>
>> Even if we force Content type to Type1, in above topology Type 0 content
>> that could be rendered to
>> HDCP1.4 compliant panel wont be rendered as that has been forcibly
>> classified as Type 1 by KMD.
> Why? HDCP_ENABLE would just give you the "best" HDCP, so we'd fall
> back to type 0 (if that's available).
I think i misinterpreted. We could enable the HDCP2.2(if supported on 
panel) for the Type 0 content. No issue on that
>> Forcing type 1 content to Type 0 will break the association of type1 content
>> to HDCP2.2 devices only.
> I didn't propose to force type1 everywhere. Why do you think this is needed.

>> More than that Devices with our indented DRM HDCP2.2 support wont pass the
>> HDCP2.2 compliance.
>> Considering we could extend the CrOS Userspace for HDCP2.2, I would prefer
>> to go ahead with
>> HDCP_ENABLE_TYPE1 along with HDCP_ENABLE.
> Yes, it's only hdcp1.4, and getting to full hdcp2.2 will take more
> work. You can do all of that in one go, but my experience with
> upstreaming new uabi is that usually that's not the most effective way
> to go about things. But in the end, that's your choice.
Agreed. We will go gradually about enabling HDCP2.2.
     1. Enable HDCP2.2 for HDCP_ENABLE with Content type as 0.
     2. Enable HDCP2.2 for Type 1 content with Enum value HDCP_ENABLE_TYPE1
     3. Making HDCP2.2 support as HDCP2.2 spec compliant.

But I think i will just add another enum value HDCP_UNSUPPORTED to mark 
the no HDCP supported on the setup.
I hope that is fine.
> -Daniel


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