vmgenc.4: add manual page for VM Generation Counter driver

[chris.longros_gmail.com]

Summary

Document the vmgenc(4) ACPI driver which detects virtual machine
cloning and snapshot restoration via the VM Generation ID
specification. The driver reseeds the kernel entropy pool when
a generation change is detected.

Signed-off-by: Christos Longros <[e-mail]>

[cem]

Text looks reasonable to me. I did not verify formatting / doc best practices (section order, etc).

[chris.longros_gmail.com]

I previewed it with

man -l ~/freebsd/freebsd-src/share/man/man4/vmgenc.4

mandoc

gives no errors.

[ziaee]

Ok from manpages, let me know what you want to do w/rt synopsis formatting.

share/man/man4/vmgenc.4

14–26

Any chance I can get you to use a more mdoc(7) conformant format? We have almost two hundred manpages that follow this format, like vt(4) or uftdi(4), and I've proposed in talks and on arch@ trying to get everything to use this consistently.

It is more consistent, concise, and has the added benefit of increased search indexing in the manpages database, and in my talk on youtube, mandoc upstream said they also support this change as a move towards greater correctness in consistency.

[chris.longros_gmail.com]

Updated SYNOPSIS to use modern .Cd format.

[ziaee]

I was doing a final look-over before commit and had some ideas that may or may not be useful.

share/man/man4/vmgenc.4

11

Does this make sense (im unfamiliar with the underlying topic)? I'm thinking maybe someone could search "virtual machine generation id" or maybe even "machine generation id", but i don't know if that's realistic or disturbs the meaning.

22

Maybe? acpi4 refers to the driver and not the underlying concept, not sure if that's true here.