Date: Sat, 24 Apr 2010 11:22:33 -0700 From: Ted Mittelstaedt <tedm@mittelstaedt.us> To: "M. Warner Losh" <imp@bsdimp.com> Cc: freebsd-hackers@freebsd.org, freebsd-drivers@freebsd.org, gljennjohn@googlemail.com Subject: Re: What tty changes - question on porting ltmdm and hcfmdm to FreeBSD 8 Message-ID: <4BD336E9.5070007@mittelstaedt.us> In-Reply-To: <20100424.092938.1125510371197586607.imp@bsdimp.com> References: <4BD22CD0.7030407@mittelstaedt.us> <20100424102255.12d782f8@ernst.jennejohn.org> <20100424.092938.1125510371197586607.imp@bsdimp.com>
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On 4/24/2010 8:29 AM, M. Warner Losh wrote: > In message:<20100424102255.12d782f8@ernst.jennejohn.org> > Gary Jennejohn<gljennjohn@googlemail.com> writes: > : On Fri, 23 Apr 2010 16:27:12 -0700 > : Ted Mittelstaedt<tedm@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 > I mailed Ed and his response is to look at the changelog of sys/dev/uart/uart_tty.c for an idea of how to rewrite the driver, so I will take a look there. The ltmdm driver was updated in 2008 for an early version of FreeBSD 8, before the TTY layer changes went in, so that's where I'll start. Ted
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