[PATCH] Add support for scrolling boot log messages

[Ray Strode]

Hey again,

I looked through your patch and have some thoughts.

One thing I don't really like in the patch is the special prefixed
messages.  Messages are supposed to be human readable, translated text
strings.

Stuff like "Press I for interactive start up" or "Press Escape to view
detailed boot messages"

We do have something that is supposed to be machine parseable. That's
'plymouth update --status=some-milestone' which tells the splash
plugins about certain distro specific events in the boot process.
It's sort of encodes the expectation that a service starts and
finishes in one go, though, so it's not ideal for capturing things
that don't start instantaneously.

We also have a way to say "there was an error during boot".  That's
'plymouth report-error'  .  It just says that there was an error,
though, giving no context about what that error is, so it's not very
useful.

Neither of these are exactly what you need, but they illustrate that
we really should have "control information" about boot progress
encoded in the protocol and not the message payloads.

I think what you're looking for is a way to tell the splash plugin
1) about a new (potentially slow) operation that is initiated
2) when and how the operation completes

So we probably need to augment the protocol to support that.
Maybe some new "register-operation" command like:

plymouth register-operation --id=some-id --name="some human readable
name here" --initial-status=some-starting-status

and then a new optional --operation-id flag to "plymouth update"

plymouth update
--operation-id=some-id-previously-passed-to-register-operation
--status the-latest-outcome-of-the-operation

This way you could do, e.g,

plymouth register-operation --id=some-random-job --name="some random
job" --initial-status=starting
plymouth  update --operation-id=some-random-job --status=finished

and the splash plugin could do

Starting some random job... [ok]

but if you did
plymouth update --operation-id=some-random-job --status=failed

then it would do

Starting some random job... [failed]

The splash plugin could keep track of which line in on the screen is
which operation and automatically add the appropriate status text to
the right line.

Make sense?

A few more thoughts:

- I don't think we would want to add those kinds of messages to the
text plugin.  the point of the text plugin, in particular.  The point
of that plugin is to hide boot messages.
- make sure the patch is against an upstream tree when submitting it upstream
- thanks for putting effort into working on plymouth. I'm sorry it
took so long to reply.  Feel free to aggresively poke me on list or in
#plymouth if I don't respond within a reasonable time frame.

--Ray