[Intel-gfx] [RFC v1 01/20] drm/hdcp: HDCP bitmask property for connectors

[Daniel Vetter]

On Thu, Jul 13, 2017 at 12:15 PM, Ramalingam C <ramalingam.c at 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 at 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 at 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).

> 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.

> 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).

> 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.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch