[PATCH 0/7] Secure display with new CRTC properties

[Simon Ser]

On Tuesday, May 16th, 2023 at 07:39, Alan Liu <HaoPing.Liu at amd.com> wrote:

> To address this problem, since modern display control hardware is able to
> calculate the CRC checksum of the display content, we are thinking of a
> feature to let userspace specify a region of interest (ROI) on display, and
> we can utilize the hardware to calculate the CRC checksum as frames scanned
> out, and finally, provide the checksum for userspace for validation purpose.
> In this case, since the icons themselves are often fixed over static
> backgrounds, the CRC of the ROI pixels can be known in advance. So one of the
> usage of ROI and corresponding CRC result is that as users know the CRC
> checksum of the tell-tales in advance, at runtime they can retrieve the CRC
> value from kernel for validation as frames are scanned out.
> 
> We implement this feature and call it secure display.

I's strongly advise *not* using the word "secure" here. "Secure" is over-loaded
with so many different meanings, as a result it's super-unclear what a KMS
property name "SECURE_FOO" would do. As an example, some people use "secure" to
refer to Digital Restrictions Management. Something like "CHECKSUM_REGION"
would much better describe the feature you want to implement IMHO.

Also, please note that IGT already extracts CRCs for testing purposes. Maybe
there's an opportunity to use the same uAPI here.