Baremetal /proc/cpuinfo

Question

I'm trying to check the revision code of a Raspberry Pi 4b, but the only instructions I can find say to get it from /proc/cpuinfo, but that's a Linux-specific answer. So far I haven't been able to find the documentation of what physical address I can read from to get the same information. Can anyone point me to a document that will tell me that, and/or an example source file that reads that value directly?

Answer 1

I found the answer in the firmware wiki (thanks to this answer). The revision number comes from mailbox 0 channel 8:

Get board revision

• Tag: 0x00010002
• Request:
  • Length: 0
• Response:
  • Length: 4
  • Value:
    • u32: board revision