freebsd stable - Nov 2010 - Are there digi(4) users running -STABLE? (was Re: Migrating ISA/PCI drivers)

[cross-posting to stable@, where some of those folk might hang out]

On Fri, 19.11.2010 at 09:21:00 +1100, Peter Jeremy
wrote:
> I'm (belatedly) looking at porting digi(4) to the MPSAFE TTY system
> and have some architectural questions.
> 
> The digi(4) driver appears to support 5 different Digi card variants,
> at least two of which exist in both ISA and PCI variants.  Looking at
> the Digi website, it appears that both PCI and ISA cards are still
> available (as well as a PCIe card which is unlikely to work with the
> current driver).  I only have access to PCI/Xem cards and so can't
> test my changes on any other card types.  I presume Digi cards are not
> that popular because noone else has shown any interest in the driver
> since the MPSAFE TTY changes were announced about 2.5 years ago.
> 
> How much effort should I invest in adapting code for other card types?
> In particular, the ISA cards use windowed memory accesses and IO ports
> where the PCI cards have a single flat memory aperture.  Removing
> support for ISA cards would simplify the code (and remove the need to
> make decisions about whether I need to do window switches in new
> code), as well as potentially allowing finer grained locks.
> 
> My options would seem to be:
> 1) Rip out the ISA support - this is the cleanest for me but maximises
>    effort for a future person wanting to support ISA Digi cards.
> 2) Carry forward the ISA code as best I can and ensure new code includes
>    appropriate window switches etc.  This maximises my effort but
>    hopefully makes it easier for someone to get ISA cards working.
> 3) Ignore the ISA code.  This is fairly easy but probably requires
>    similar effort to (1) to get it going on ISA since all the code
>    would need to be reviewed to add necessary ISA-specific locking/
>    window switching.
> 
> My preference is 1 since it leaves the least cruft (from my point of
> view) in the code and doesn't give users the false impression that
> ISA cards work.
> 
> I would appreciate some advice on the best way forward.  In the
> absence of any input, I will probably stick with option 3 for now but
> may move to option 1 if the ISA code starts getting in the way.  Keep
> in mind that digi(4) does not currently compile on FreeBSD-8 or later,
> so any of the above options are an improvement over the status quo,
> though all are a regression from FreeBSD-7.
> 
> Of course, if someone has access to other Digi card types and wants
> to assist with porting and testing, I would be happy to work with them.
> 
> -- 
> Peter Jeremy