Add a modifier 'DRM_FORMAT_MOD_ARM_PROTECTED' which denotes that the framebuffer is allocated in a protected system memory. Essentially, we want to support EGL_EXT_protected_content in our komeda driver.
Signed-off-by: Ayan Kumar Halder ayan.halder@arm.com
/-- Note to reviewer Komeda driver is capable of rendering DRM (Digital Rights Management) protected content. The DRM content is stored in a framebuffer allocated in system memory (which needs some special hardware signals for access).
Let us ignore how the protected system memory is allocated and for the scope of this discussion, we want to figure out the best way possible for the userspace to communicate to the drm driver to turn the protected mode on (for accessing the framebuffer with the DRM content) or off.
The possible ways by which the userspace could achieve this is via:-
1. Modifiers :- This looks to me the best way by which the userspace can communicate to the kernel to turn the protected mode on for the komeda driver as it is going to access one of the protected framebuffers. The only problem is that the current modifiers describe the tiling/compression format. However, it does not hurt to extend the meaning of modifiers to denote other attributes of the framebuffer as well.
The other reason is that on Android, we get an info from Gralloc (GRALLOC_USAGE_PROTECTED) which tells us that the buffer is protected. This can be used to set up the modifier/s (AddFB2) during framebuffer creation.
2. Framebuffer flags :- As of today, this can be one of the two values ie (DRM_MODE_FB_INTERLACED/DRM_MODE_FB_MODIFIERS). Unlike modifiers, the drm framebuffer flags are generic to the drm subsystem and ideally we should not introduce any driver specific constraint/feature.
3. Connector property:- I could see the following properties used for DRM protected content:- DRM_MODE_CONTENT_PROTECTION_DESIRED / ENABLED :- "This property is used by userspace to request the kernel protect future content communicated over the link". Clearly, we are not concerned with the protection attributes of the transmitter. So, we cannot use this property for our case.
4. DRM plane property:- Again, we want to communicate that the framebuffer(which can be attached to any plane) is protected. So introducing a new plane property does not help.
5. DRM crtc property:- For the same reason as above, introducing a new crtc property does not help.
--/
--- include/uapi/drm/drm_fourcc.h | 9 +++++++++ 1 file changed, 9 insertions(+)
diff --git a/include/uapi/drm/drm_fourcc.h b/include/uapi/drm/drm_fourcc.h index 3feeaa3f987a..38e5e81d11fe 100644 --- a/include/uapi/drm/drm_fourcc.h +++ b/include/uapi/drm/drm_fourcc.h @@ -742,6 +742,15 @@ extern "C" { */ #define AFBC_FORMAT_MOD_BCH (1ULL << 11)
+/* + * Protected framebuffer + * + * The framebuffer is allocated in a protected system memory which can be accessed + * via some special hardware signals from the dpu. This is used to support + * 'GRALLOC_USAGE_PROTECTED' in our framebuffer for EGL_EXT_protected_content. + */ +#define DRM_FORMAT_MOD_ARM_PROTECTED fourcc_mod_code(ARM, (1ULL << 55)) + /* * Allwinner tiled modifier *