[RFC] Dropping Alpha sparse mapping support from X

[Matt Turner]

Thanks for the responses, everyone.

On Fri, Sep 4, 2009 at 6:04 PM, Maciej W. Rozycki<macro at linux-mips.org> wrote:
> On Thu, 3 Sep 2009, Matt Turner wrote:
>
>> I'd like to drop support for non-BWX Alphas (EV4 and original EV5)
>> from X. These machines can't load/store to single bytes and require
>> special sparse memory mappings.
>>
>> The code required to select which functions (sparse, dense) is
>> convoluted, adds an extra layer of indirection, probably gets close to
>> zero usage, and even less testing.
>>
>> Does anyone use X on EV4 or EV5 (not EV56, EV56 has BWX)?
>
>  What's the problem with making it a build-time option?  You may inline
> the indirection based on a macro or suchlike and keep the more complicated
> code for a reference, even if you don't get any bug reports for a while
> (perhaps the code is perfect? ;) ).  Linux is probably going to support
> pre-BWX machines as long as the Alpha port itself and you may have
> troubles reaching all the interested users, especially as not everyone
> makes frequent upgrades.

After reading this and discussing it with a lot of people on IRC, I
think you're right: a build time option probably is the best choice.

Wrapping appropriate parts in #ifdef __alpha_bwx__ should do the
trick, but would require binary distributions to provide two binaries.
But since we might not have any binary distros with Debian exiting the
alpha scene, this shouldn't be a problem.

Thoughts?

>  Personally, I have planned to make the DEC 3000 AXP (that's the
> TURBOchannel family maxing out at EV45) Linux port going for a while now
> and will most likely get at it once I'm done with some VAX/Linux fiddling
> I'm currently involved with.  Linux already supports a number of
> TURBOchannel framebuffers for the MIPS port (for the purpose of
> DECstations), including but not limited to the SFB+ board which works with
> the TGA driver, and the drivers will work as soon as platform support code
> has been done -- there shouldn't be any platform-specific code left in the
> TURBOchannel drivers these days anymore.

On a different note, I've got a VAX 4000 model 60 I could use to help,
when you get that far.

Thanks,
Matt Turner