Thoughts on software-defined silicon [LWN.net]

Thoughts on software-defined silicon

Posted Feb 19, 2022 8:14 UTC (Sat) by gioele (subscriber, #61675)
Parent article: Thoughts on software-defined silicon

Just for historical context: somewhat similarly to Intel Upgrade Service, Raspberry Pis until version 4 used to come with disabled MPEG-2 and VC-1 hardware acceleration blocks. To enable them you needed to buy a key [1,2]. The firmware took care of uploading the key to the right HW register.

[1] https://codecs.raspberrypi.com/mpeg-2-license-key/
[2] https://codecs.raspberrypi.com/vc-1-license-key/

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Thoughts on software-defined silicon

Posted Feb 19, 2022 18:01 UTC (Sat) by ermo (subscriber, #86690) [Link] (1 responses)

Out of curiosity, why was this handled like this?

Was it because the IP for the hardware blocks in question was owned by someone else than the SoC supplier (MPEG LA vs. Broadcom) in this instance and that, due to wanting to keep the BoM as low as possible to hit the intended RPi price point, this was necessary for the RPi foundation?

Or am I getting it all backwards?

Thoughts on software-defined silicon

Posted Feb 19, 2022 18:24 UTC (Sat) by excors (subscriber, #95769) [Link]

Because of the MPEG LA patent licensing fees. From https://www.raspberrypi.com/news/new-video-features/ :

> One of the things that we had to regretfully dismiss as an option was an MPEG-2 decode licence for every unit. Providing that licence would have raised the price of every Raspberry Pi by roughly 10%

> We’ve spent some months working out how on earth to square this particular circle. A blanket licence for everybody would cost the Foundation money it simply doesn’t have, and not everybody with a Raspberry Pi would use that licence; an individual licence for an individual user to download and use with an individual machine is a surprisingly finickity thing to engineer. [...] But that’s what we’ve done

(They already paid a blanket licence fee for H.264 decode/encode, so that was enabled by default.)

I don't believe the individual licence key is used by the hardware blocks in any way; it's merely verified by the Pi's proprietary firmware before enabling the APIs that make the hardware accessible from Linux. Some naughty people hacked the firmware so the verification function would always return true - it's not particularly secure, but it was apparently good enough to keep the MPEG LA happy.