In the handbook (http://www.freebsd.org/doc/en/books/developers-handbook/kerneldebug-online-ddb.html):
> There is an option available for serial consoles that allows the use of a serial line BREAK on the console line to enter DDB (options BREAK_TO_DEBUGGER in the kernel config file).
This option has been modified to control the default value of the
debug.kdb.break_to_debugger tunable, which controls both serial and video console debugger behaviour.
ddb(4) may benefit from a mention
kernel config NOTES files have incorrect information (jmg@ is looking at that)
thanks for filing the report. I'd love to see more activity from developers on "their" handbook. ;) I've re-categorized it as a documentation bug.
Could you provide a writeup (doesn't have to be in XML, we doc folks can do that) for the changes you're proposing? You can also send us a review on Phabricator if that is easier for you.
I still need to figure out exactly what the update should be; I submitted this ticket while working with jmg upon discovery that the handbook doesn't match the implementation.
Developers should indeed be updating the documentation as they make these changes.
Anyhow, I will update this or submit a Phabricator review once I have a handle on what the change should be.