[Intel-gfx] [RFC v3] drm/hdcp: drm enum property for CP State
C, Ramalingam
ramalingam.c at intel.com
Wed Jul 26 16:51:50 UTC 2017
> -----Original Message-----
> From: Sean Paul [mailto:seanpaul at chromium.org]
> Sent: Wednesday, July 26, 2017 8:23 PM
> To: C, Ramalingam <ramalingam.c at intel.com>
> Cc: Sean Paul <seanpaul at chromium.org>; Vetter, Daniel
> <daniel.vetter at intel.com>; Intel Graphics Development <intel-
> gfx at lists.freedesktop.org>; dri-devel <dri-devel at lists.freedesktop.org>; Daniel
> Vetter <daniel at ffwll.ch>
> Subject: Re: [RFC v3] drm/hdcp: drm enum property for CP State
>
> On Wed, Jul 26, 2017 at 03:24:10PM +0530, Ramalingam C wrote:
> >
> >
> > On Tuesday 25 July 2017 06:04 PM, Sean Paul wrote:
> > > On Mon, Jul 24, 2017 at 2:12 PM, Ramalingam C <ramalingam.c at intel.com>
> wrote:
> > > > DRM connector property is created to represent the content
> > > > protection state of the connector and to configure the same.
> > > >
> > > > Content protection states defined:
> > > > DRM_MODE_CONTENT_PROTECTION_UNSUPPORTED -
> Unsupported
> > > > DRM_MODE_CONTENT_PROTECTION_DISABLE - Disabled
> > > > DRM_MODE_CONTENT_PROTECTION_ENABLE - Enabled
> > > >
> > > > v2: Redesigned the property to match with CP needs of CrOS [Sean].
> > > >
> > > > v3: Renamed the state names. Header is removed [sean].
> > > >
> > > > Signed-off-by: Ramalingam C <ramalingam.c at intel.com>
> > > > ---
> > > > drivers/gpu/drm/drm_connector.c | 14 ++++++++++++++
> > > > include/drm/drm_mode_config.h | 5 +++++
> > > > include/uapi/drm/drm_mode.h | 5 +++++
> > > > 3 files changed, 24 insertions(+)
> > > >
> > > > diff --git a/drivers/gpu/drm/drm_connector.c
> > > > b/drivers/gpu/drm/drm_connector.c index 5cd61af..d6aaa08 100644
> > > > --- a/drivers/gpu/drm/drm_connector.c
> > > > +++ b/drivers/gpu/drm/drm_connector.c
> > > > @@ -617,6 +617,13 @@ static const struct drm_prop_enum_list
> drm_link_status_enum_list[] = {
> > > > };
> > > > DRM_ENUM_NAME_FN(drm_get_link_status_name,
> > > > drm_link_status_enum_list)
> > > >
> > > > +static const struct drm_prop_enum_list drm_cp_enum_list[] = {
> > > > + { DRM_MODE_CONTENT_PROTECTION_UNSUPPORTED,
> "Unsupported" },
> > > You're still changing the enum names from the original patch/CrOS
> > > implementation.
> > >
> > > https://lists.freedesktop.org/archives/dri-devel/2014-December/07333
> > > 6.html
> > >
> > > https://cs.chromium.org/chromium/src/ui/ozone/platform/drm/gpu/drm_d
> > > isplay.cc?l=27
> >
> > Sean,
> >
> > I think we have bit of confusion here.
>
> Agreed :)
>
> >
> > And in previous discussion you were fine with new state of property
> > that is "unsupported" - indicates no common HDCP version is supported
> > on HDCP src and Sink combo.
> >
> > when CP is not possible, if property exist, userspace will interpret
> > it as CP is supported and attempt for enabling.
> > I prefer indicating Unsupported state than failing such requests blindly.
> >
> > In that case to interpret the new state, we need to change CrOS User
> > space code.
> >
> > In the RFC you mentioned above, two version of uapi interfaces are
> > discussed.
> > V1 uses single property to configure the CP and also for
> > status indication.
> > V2 uses two properties one for configuring and another one for
> > status of Content protection.
> >
> > But CrOS user space is currently using the V1 interface.
> >
> > which will be preferred approach right now (V1/V2)?
> > In either way we need to change the CrOS :(
>
> We can't upstream code without a userspace implementation, so V1. Without
> any modifications.
Based on uAPI rules mentioned by Daniel, what I infer is that once a uAPI is in place,
usecase of uAPI cant be changed. It can be only be extended for future needs.
So IMHO it is better to shape the userspace as per the uAPI
interfaces that community want to have for longer run. And mainly we should adapt to a
interface which can be conveniently extended for HDCP2.2 and future specs versions.
So IMO it is worth seeing what it takes for CrOS Userspace changes for HDCP2.2 interfaces.
And In the interest of having HDCP2.2 in their stack sooner, if the CrOS community or Google
is interested in providing that userspace support, it will be smoother to put the
complete and preferred uAPI for HDCP2.2 and 1.4 in place.
Sean, I think you will be better person to comment on this from both sides, CrOS and DRM.
>
> As has been mentioned before in this thread, it's a lot easier to upstream code
> that is proven to work, than it is to merge speculative API. Further, if this patch
> were merged, it would be CrOS which is currently the only consumer... not a
> good look :)
Not exactly. CrOS will be the first consumer, Android will follow soon after this.
We need to enable this feature on HwC for that purpose. Yup might take required time :)
>
>
> >
> > Lets say we need to modify CrOS user space, will there be any help for that?
> > I am not aware what it takes though.
>
> You could probably reach out to chromium-dev at chromium.org or the author of
> the Chrome hdcp implementation for help.
Thank you for the contact.
And before reaching out, it is better to conclude the HDCP1.4/2.2 uAPI interfaces that is agreeable for this community.
In that perspective, can we consider and review the uAPI interface with two properties discussed for V2 of your earlier patches?
Complete use case is discussed in my previous mail.
Based on userspace commitment for HDCP2.2, we can add blob property for SRM too.
>
> Sean
>
> >
> > I am trying to discuss both uapi versions of V1 and V2. I prefer V2 though.
> >
> > If V1 is preferred we need a single property as below "content
> > protection" property with {"Unsupported", "Undesired", "Desired",
> > "Enabled"}
> > "Type1_desired" and "Type1_Enabled" are needed
> > for
> > HDCP2.2
> >
> >
> > If V2 is preferred we need two properties as below
> >
> > "content protection" property with {"Unsupported", "Undesired", "Desired"}
> > ("Type1_desired" - needed For HDCP2.2) "content protection
> > status" property with {"Disabled", "Enabled"}
> > ("Type1_enabled" - needed for HDCP2.2)
This uAPI interface looks fit to serve the all needs of HDCP1.4 and 2.2 as explained below.
Sean and Daniel,
I request you to share your views. Thanks.
--Ram
> >
> > - Not providing the ksv, as reflecting one ksv is not serving any
> > purpose.
> > Even for revocation check you need provision to list all
> > device IDs (Max 32devices x 5Bytes ID) attached to repeater.
> > So it is good to reflect the current protection level of
> > link through enum.
> >
> > And Usage will be as below:
> > By default property "content protection" will be set to
> > - "Unsupported" (If CP is not possible on the Link)
> > - "Undesired" (If Link is not protected. CP is possible)
> > By default property "content protection status" will be set to
> > - "Disabled"
> >
> > the sequence of enabling protection on a link:
> > - User space will set "content protection" "Undesired" -> "Desired"
> > - kernel will start the Authentication.
> > - Once Auth is successful, kernel will change "content
> > protection status" as "Disabled" -> "Enabled"
> >
> > The sequence of disabling protection on a link:
> > - User space will set "content protection" "Desired" -> "Undesired"
> > - kernel will start the disable encryption.
> > - Once it is successful, kernel will change "content
> > protection status" as "Enabled" -> "Disabled"
> >
> > The sequence in case of encryption Failure on protected link:
> > - When Failure of encryption occurs, kernel will change
> > "content protection status" as "Enabled" -> "Disabled"
> > - Kernel will try for retry for authentication and encryption.
> > - If the link is encrypted once again, kernel will
> > change "content protection status" as "Disabled" -> "Enabled"
> > - But if retry failed, kernel will change "content
> > protection" as "Desired" -> "Undesired"
> > - So the "Desired" state of "content protection" property
> > indicates that kernel is authenticating/re authenticating the link for encryption.
> >
> > --Ram
> > >
> > >
> > >
> > > > + { DRM_MODE_CONTENT_PROTECTION_DISABLE, "Disabled" },
> > > > + { DRM_MODE_CONTENT_PROTECTION_ENABLE, "Enabled" },
> > > > +};
> > > > +DRM_ENUM_NAME_FN(drm_get_cp_status_name, drm_cp_enum_list)
> > > > +
> > > > /**
> > > > * drm_display_info_set_bus_formats - set the supported bus formats
> > > > * @info: display info to store bus formats in @@ -789,6 +796,13
> > > > @@ int drm_connector_create_standard_properties(struct drm_device
> *dev)
> > > > return -ENOMEM;
> > > > dev->mode_config.link_status_property = prop;
> > > >
> > > > + prop = drm_property_create_enum(dev, 0, "Content Protection",
> > > > + drm_cp_enum_list,
> > > > + ARRAY_SIZE(drm_cp_enum_list));
> > > > + if (!prop)
> > > > + return -ENOMEM;
> > > > + dev->mode_config.cp_property = prop;
> > > > +
> > > > return 0;
> > > > }
> > > >
> > > > diff --git a/include/drm/drm_mode_config.h
> > > > b/include/drm/drm_mode_config.h index 4298171..7acb8b2 100644
> > > > --- a/include/drm/drm_mode_config.h
> > > > +++ b/include/drm/drm_mode_config.h
> > > > @@ -538,6 +538,11 @@ struct drm_mode_config {
> > > > */
> > > > struct drm_property *link_status_property;
> > > > /**
> > > > + * @cp_property: Default connector property for CP
> > > > + * of a connector
> > > Can you please elaborate on this, so readers can understand how this
> > > property works? Perhaps just copy the docs from the original patch?
> > >
> > > > + */
> > > > + struct drm_property *cp_property;
> > > > + /**
> > > > * @plane_type_property: Default plane property to differentiate
> > > > * CURSOR, PRIMARY and OVERLAY legacy uses of planes.
> > > > */
> > > > diff --git a/include/uapi/drm/drm_mode.h
> > > > b/include/uapi/drm/drm_mode.h index 403339f..554a770 100644
> > > > --- a/include/uapi/drm/drm_mode.h
> > > > +++ b/include/uapi/drm/drm_mode.h
> > > > @@ -127,6 +127,11 @@ extern "C" {
> > > > #define DRM_MODE_LINK_STATUS_GOOD 0
> > > > #define DRM_MODE_LINK_STATUS_BAD 1
> > > >
> > > > +/* Content Protection options */
> > > > +#define DRM_MODE_CONTENT_PROTECTION_UNSUPPORTED 0
> > > > +#define DRM_MODE_CONTENT_PROTECTION_DISABLE 1
> > > > +#define DRM_MODE_CONTENT_PROTECTION_ENABLE 2
> > > > +
> > > > /*
> > > > * DRM_MODE_ROTATE_<degrees>
> > > > *
> > > > --
> > > > 2.7.4
> > > >
> >
>
> --
> Sean Paul, Software Engineer, Google / Chromium OS
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