Re: port-vax/58261

On 2024-06-10 00:18, David Brownlee wrote:
> On Sun, 9 Jun 2024 at 19:37, matthew green <[email protected]> wrote:
>>
>>    magic numbers could be named, "vax_cpudata & 0xff" could become a
>>    macro (GET_SIE_MICROCODE_VER(x)?)
> 
> Sometimes the ucode rev is in 0xff (which is accessed sometimes as "&
> 0xff", "& 0377", and my favourite "% 0377" :), and sometimes the
> hardware3 rev is in 0xff, and ucode rev in 0xff00. Its common enough
> that I think it's worth a macro, with a /* usually, not always */
> comment

If anyone did "% 0377" that would be a bug. It's a different thing. 
However, if they did "% 0400" it would be fine, and I would suspect the 
compiler would reduce that to an AND (or actually a BICL in VAX 
assembly) in the end anyway.

> Actually, looking again I really rather like the approach in
> vax/ka780.c:345 - create a bitflag struct for sid
> 
> struct ka78x {
>          unsigned snr:12,
>                   plant:3,
>                   eco:8,
>                   v785:1,
>                   type:8;
> };
> 
> and then use
> 
>          aprint_normal(": KA%s, S/N %d(%d), hardware ECO level %d(%d)\n",
>              cpu_getmodel() + 7, ka78->snr, ka78->plant, ka78->eco >>
> 4, ka78->eco);

I do agree that using a bitfield is a very reasonable approach for this, 
and I did the same for the ka86. But looking at the quoted lines above, 
I really think eco should be split in two parts instead of the shifting. 
That seems just silly, if that really is two different numbers to the eco.
Also, cpu_getmodel() returns a string, and then 7 is added to that 
pointer. That seems rather horrible coding, and I think that should also 
be cleaned up a bit. But that's not really a part of your work, so I 
wouldn't worry about that here.

However, again - I think changing to use bitfields for these kind of 
things make the code much cleaner.

   Johnny

-- 
Johnny Billquist                  || "I'm on a bus
                                   ||  on a psychedelic trip
email: [email protected]             ||  Reading murder books
pdp is alive!                     ||  tryin' to stay hip" - B. Idol