What tty changes - question on porting ltmdm and hcfmdm to FreeBSD 8

[M. Warner Losh]

In message: <20100424102255.12d782f8 at ernst.jennejohn.org>
            Gary Jennejohn <gljennjohn at googlemail.com> writes:
: On Fri, 23 Apr 2010 16:27:12 -0700
: Ted Mittelstaedt <tedm at mittelstaedt.us> wrote:
: 
: >   Setting aside the question of why do we break software that a lot of 
: > people use
: > (these chips are in use on a lot of laptops) is there a document 
: > somewhere that explains
: > what changes need to be made in code for this new tty setup?  Or, is 
: > there a set
: > of magic include files or a "conversion shim" library that will allow 
: > these kinds
: > of programs to build without much work?
: > 
: >   Or is porting these drivers just so non-trivial that the only way is 
: > to just delve into
: > the system manuals and delve into the driver code and try to figure out 
: > what is
: > going on in each?  If that's the case that's probably beyond my ability 
: > but I'd
: > be happy to serve as a testbed.
: > 
: 
: The guy to ask about this would be Ed Schouten (ed@). AFAICR he did the new
: TTY stuff.  I don't know whether he reads these lists.
: 
: AFAIK there is no easy way to fix this and there are no backwards compati-
: bilty shims or magic header files.
: 
: The fundamental problem with ltmdm is that it's a KLD and has to grovel
: around in the guts of the kernel.  That makes fixing it decidely non-
: trivial.

The fundamental reason that things changed was due to the locking of
the TTY layer.  These things change over time, and the old APIs made
it very difficult to lock without driver visible changes.

Warner