[Intel-gfx] [PATCH v9 10/39] drm/i915: Implement HDCP2.2 receiver authentication

[Daniel Vetter]

On Wed, Dec 19, 2018 at 08:35:48PM +0530, C, Ramalingam wrote:
> On 12/19/2018 8:05 PM, Daniel Vetter wrote:
> > On Thu, Dec 13, 2018 at 09:31:12AM +0530, Ramalingam C wrote:
> > > +	if (!hdcp->is_repeater && shim->config_stream_type) {
> > > +		/*
> > > +		 * Errata for DP: As Stream type is used for encryption,
> > > +		 * Receiver should be communicated with stream type for the
> > > +		 * decryption of the content.
> > > +		 * Repeater will be communicated with stream type as a
> > > +		 * part of it's auth later in time.
> > > +		 */
> > I'm not following what you want to say with this comment, and haven't
> > found anything in the hdcp2 dp spec about this either.
> 
> this is there in the errata of DP HDCP2.2 spec.
> hdcp2.2 encryption algo involves the stream type as a parameter.
> And as part of hdcp auth mentioned in base spec DP repeaters receive that details to decrypt the content.
> But DP receivers dont get it. So errata adds the missing piece for decryption.

Ok I found it, but the fake HDCP_2_2_ERRATA_DP_STREAM_TYPE define is kinda
annoying. It doesn't exist in the spec, but we put it into the drm_hdcp.h
header. Since you have a special ->config_stream_type hook for this
anyway, and it's only needed for DP, please move that into the shim
implementation.

And then a follow-up patch to remove the fake #define from drm_hdcp.h.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch