On Mon, 8 Jul 2019 14:42:29 +0530
Ramalingam C <ramalingam.c@xxxxxxxxx> wrote:
> On 2019-07-08 at 12:59:59 +0300, Pekka Paalanen wrote:
> > On Mon, 8 Jul 2019 12:52:17 +0300
> > Pekka Paalanen <ppaalanen@xxxxxxxxx> wrote:
> >
> > > On Fri, 5 Jul 2019 06:16:37 +0530
> > > Ramalingam C <ramalingam.c@xxxxxxxxx> wrote:
> > >
> > > > This patch adds a DRM ENUM property to the selected connectors.
> > > > This property is used for mentioning the protected content's type
> > > > from userspace to kernel HDCP authentication.
> > > >
> > > > Type of the stream is decided by the protected content providers.
> > > > Type 0 content can be rendered on any HDCP protected display wires.
> > > > But Type 1 content can be rendered only on HDCP2.2 protected paths.
> > > >
> > > > So when a userspace sets this property to Type 1 and starts the HDCP
> > > > enable, kernel will honour it only if HDCP2.2 authentication is through
> > > > for type 1. Else HDCP enable will be failed.
> > > >
> > > > Need ACK for this new conenctor property from userspace consumer.
> > > >
> > > > v2:
> > > > cp_content_type is replaced with content_protection_type [daniel]
> > > > check at atomic_set_property is removed [Maarten]
> > > > v3:
> > > > %s/content_protection_type/hdcp_content_type [Pekka]
> > > > v4:
> > > > property is created for the first requested connector and then reused.
> > > > [Danvet]
> > > > v5:
> > > > kernel doc nits addressed [Daniel]
> > > > Rebased as part of patch reordering.
> > > > v6:
> > > > Kernel docs are modified [pekka]
> > > >
> > > > Signed-off-by: Ramalingam C <ramalingam.c@xxxxxxxxx>
> > > > Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
> > > > ---
> > > > drivers/gpu/drm/drm_atomic_uapi.c | 4 +++
> > > > drivers/gpu/drm/drm_connector.c | 22 ++++++++++++++
> > > > drivers/gpu/drm/drm_hdcp.c | 36 ++++++++++++++++++++++-
> > > > drivers/gpu/drm/i915/display/intel_hdcp.c | 4 ++-
> > > > include/drm/drm_connector.h | 7 +++++
> > > > include/drm/drm_hdcp.h | 2 +-
> > > > include/drm/drm_mode_config.h | 6 ++++
> > > > include/uapi/drm/drm_mode.h | 4 +++
> > > > 8 files changed, 82 insertions(+), 3 deletions(-)
> > > >
> > > > diff --git a/drivers/gpu/drm/drm_atomic_uapi.c b/drivers/gpu/drm/drm_atomic_uapi.c
> > > > index abe38bdf85ae..19ae119f1a5d 100644
> > > > --- a/drivers/gpu/drm/drm_atomic_uapi.c
> > > > +++ b/drivers/gpu/drm/drm_atomic_uapi.c
> > > > @@ -747,6 +747,8 @@ static int drm_atomic_connector_set_property(struct drm_connector *connector,
> > > > return -EINVAL;
> > > > }
> > > > state->content_protection = val;
> > > > + } else if (property == config->hdcp_content_type_property) {
> > > > + state->hdcp_content_type = val;
> > > > } else if (property == connector->colorspace_property) {
> > > > state->colorspace = val;
> > > > } else if (property == config->writeback_fb_id_property) {
> > > > @@ -831,6 +833,8 @@ drm_atomic_connector_get_property(struct drm_connector *connector,
> > > > state->hdr_output_metadata->base.id : 0;
> > > > } else if (property == config->content_protection_property) {
> > > > *val = state->content_protection;
> > > > + } else if (property == config->hdcp_content_type_property) {
> > > > + *val = state->hdcp_content_type;
> > > > } else if (property == config->writeback_fb_id_property) {
> > > > /* Writeback framebuffer is one-shot, write and forget */
> > > > *val = 0;
> > > > diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c
> > > > index 068d4b05f1be..17aef88c03a6 100644
> > > > --- a/drivers/gpu/drm/drm_connector.c
> > > > +++ b/drivers/gpu/drm/drm_connector.c
> > > > @@ -951,6 +951,28 @@ static const struct drm_prop_enum_list hdmi_colorspaces[] = {
> > > > * the value transitions from ENABLED to DESIRED. This signifies the link
> > > > * is no longer protected and userspace should take appropriate action
> > > > * (whatever that might be).
> > > > + * HDCP Content Type:
> > > > + * This property is used by the userspace to configure the kernel with
> > > > + * to be displayed stream's content type. Content Type of a stream is
> > > > + * decided by the owner of the stream, as "HDCP Type0" or "HDCP Type1".
> > > > + *
> > > > + * The value of the property can be one the below:
> > > > + * - "HDCP Type0": DRM_MODE_HDCP_CONTENT_TYPE0 = 0
> > > > + * HDCP Type0 streams can be transmitted on a link which is
> > > > + * encrypted with HDCP 1.4 or higher versions of HDCP(i.e HDCP2.2
> > > > + * and more).
> > > > + * - "HDCP Type1": DRM_MODE_HDCP_CONTENT_TYPE1 = 1
> > > > + * HDCP Type1 streams can be transmitted on a link which is
> > > > + * encrypted only with HDCP 2.2. In future higher versions also
> > > > + * might support Type1 based on their spec.
> > > > + *
> > > > + * Note that the HDCP Content Type property is introduced at HDCP 2.2, and
> > > > + * defaults to type 0. It is only exposed by drivers supporting HDCP 2.2.
> > > > + * Based on how next versions of HDCP specs are defined content Type could
> > > > + * be used for higher versions too.
> > > > + * If content type is changed when content_protection is not UNDESIRED,
> > > > + * then kernel will disable the HDCP and re-enable with new type in the
> > > > + * same atomic commit
> > >
> > > Hi,
> > >
> > > I think this doc covers all my previous comments on this patch now. One
> > > more thing, the wording here reads as:
> > > - userspace configures the content type
> > > - the kernel transmits the content if the link satisfies the type
> > > requirement
> > > - if the link does not satisfy the type requirement, the kernel will
> > > not transmit the content
> > >
> > > This is of course false, the kernel transmits anyway, but that is how
> > > the text reads from the "stream's content type" and "can be transmitted
> > > on". The problem is, that a userspace developer will think the stream
> > > is what he pushes into KMS, not what goes on the wire. The text also
> > > magnifies that misconception because it sounds like the stream is
> > > something different from the link. Actually, I don't understand what
> > > "the stream" is supposed to be here.
> Stream is nothing but the any display content that needs the hdcp
> protection.
> > >
> > > Instead, I think you should explain how the content type property
> > > guides the kernel driver's attempts in negotiating the link encryption
> > > and how that then reflects in the content protection property (DESIRED
> > > vs. ENABLED). It might be best to not say anything about any "stream".
>
> I will explain in different and more words, so that this questions wont
> raise.
> >
> > Btw. this UAPI has the following fundamental flaws:
> >
> > - userspace cannot know which encryption is used on the link
> This claim is not true.
>
> "HDCP content type" and "content protection" are used
> together in
> requesting the HDCP state
> confirming that required state is achieved
> For ex:
> The state "HDCP content type" = "HDCP Type1" and "content protection" =
> "DESIRED" stands for userspace has requested for HDCP Type 1 protection
> from kernel.
>
> When kernel changes the "content protection" to "ENABLED" when "HDCP
> content type" is "HDCP Type1", kernel indicates the userspace that HDCP
> authentication for Type 1 is successful.
>
> I am not sure why do you think that userspace is not knowing link's
> authentication state w.r.t type.
Hi,
if userspace asks for Type0, the kernel is free to use Type1 instead
and switch "Content Protection" to "ENABLED". Userspace has no way of
knowing that the link actually runs with Type1.
You can argue that it does not matter, because Type1 protection is
stronger than Type0, so everybody should be happy, but that does not
change the fact that userspace thinks wrong of what the protection
really is.
> > - userspace cannot force Type0 if the driver succeeds enabling Type1
> When you set Type 0, kernel will authenticate the link for Type 0 only.
Really? Sorry, I have completely missed this. Please make it clear in
UAPI and kAPI docs. This invalidates my comment above as well.
But you are also conflicting with your own doc, which said:
+ * - "HDCP Type0": DRM_MODE_HDCP_CONTENT_TYPE0 = 0
+ * HDCP Type0 streams can be transmitted on a link which is
+ * encrypted with HDCP 1.4 or higher versions of HDCP(i.e HDCP2.2
+ * and more).
To me that reads as: if userspace asks for Type0, the kernel is free to
use Type0 or Type1 or anything stronger to say it succeeded.
Hence my confusion.
> Not for Type 1. I guess you are trying to say HDCP1.4 is not possible
> over HDCP2.2.
I wouldn't know what that means.
> I dont see any reason why anyone want this except for testing.
>
> Type 0 can be achieved through HDCP2.2 and HDCP1.4. And HDCP2.2 is attempted
> first and HDCP1.4 will be attempted only if HDCP2.2 is failed for some
> reasons. This is done because HDCP2.2 is preferred over 1.4 due to its
> better crypto algo.
I'm running with the assumption that:
- Type0 == HDCP 1.4
- Type1 == HDCP 2.2
and I have no idea why you are sometimes talking about Type and
sometimes about HDCP version.
Is there any reason to actually talk about HDCP versions at all in the
UAPI doc? I'm starting to suspect that my assumptions are not right,
and the use of dual-terminology in the UAPI doc confuses me.
> Thanks for pointing it out. There is a scope to add all these
> information in the documentation. Which I will do it in the next version
> today.
Awesome, let's see.
Thanks,
pq
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