On Thu, 11 Jul 2019 10:18:22 -0400 Sean Paul <s...@poorly.run> wrote:
> On Mon, Jul 08, 2019 at 04:51:11PM +0530, Ramalingam C 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. ... > > diff --git a/drivers/gpu/drm/drm_connector.c > > b/drivers/gpu/drm/drm_connector.c > > index 068d4b05f1be..732f6645643d 100644 > > --- a/drivers/gpu/drm/drm_connector.c > > +++ b/drivers/gpu/drm/drm_connector.c > > @@ -952,6 +952,45 @@ static const struct drm_prop_enum_list > > hdmi_colorspaces[] = { > > * is no longer protected and userspace should take appropriate action > > * (whatever that might be). > > * > > + * HDCP Content Type: > > + * This Enum property is used by the userspace to declare the content type > > + * of the display stream, to kernel. Here display stream stands for any > > + * display content that userspace intended to render with HDCP encryption. > > + * > > + * 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 Type1": DRM_MODE_HDCP_CONTENT_TYPE1 = 1 > > + * > > + * When kernel starts the HDCP authentication upon the "DESIRED" state of > > + * the "Content Protection", it refers the "HDCP Content Type" property > > + * state. And perform the HDCP authentication with the display sink for > > + * the content type mentioned by "HDCP Content Type". > > + * > > + * Stream classified as HDCP Type0 can be transmitted on a link which is > > + * encrypted with HDCP 1.4 or higher versions of HDCP(i.e HDCP2.2 > > + * and more). > > + * > > + * Streams classified as HDCP Type1 can be transmitted on a link which is > > + * encrypted only with HDCP 2.2. In future, HDCP versions >2.2 also might > > + * support Type1 based on their spec. > > + * > > + * HDCP2.2 authentication protocol itself takes the "Content Type" as a > > + * parameter, which is a input for the DP HDCP2.2 encryption algo. > > + * > > + * 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. And when "Content Protection" is ENABLED, it means > > + * that link is HDCP authenticated and encrypted, for the transmission of > > + * the Type of stream mentioned at "HDCP Content Type". > > + * > > * HDR_OUTPUT_METADATA: > > * Connector property to enable userspace to send HDR Metadata to > > * driver. This metadata is based on the composition and blending > > Do we actually need an entirely new property? Can't we just add a new > entry to the existing Content Protection property which is "Desired Type1" or > similar? The kernel will then either attempt 2.2 auth or it will ignore it the > request if it's not supported. Hi, IMHO the existing "Content Protection" property is already complicated enough that one should not add anything new to it. If you added "desired-type-1", the readback of it would become ambiguous if it was "ENABLED", userspace would not know if the value written was "DESIRED" or "desired-type-1". Sure, it's not a problem when a display server knows what it just wrote into it, but shouldn't we try to keep KMS state readable as well, if for nothing but debugging? I think using the same property for communicating in both directions between the kernel and userspace (value can be set by both userspace and kernel at times) was a mistake to begin with. It has already caused long discussions on what the readback actually should reflect and whether there are races for a given userspace implementation. Thanks, pq
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