Subject: Re: [PATCH net-next 2/5] eth: fbnic: add initial PHC support

From: Jakub Kicinski <[email-masked]>
Date: Wed, 11 Sep 2024 15:25:39 -0700

On Wed, 11 Sep 2024 22:45:11 +0200 Andrew Lunn wrote:
> > > That's good question. Do we need another set of helpers just because of 
> > > names? Obviously, the internals will be the same sequence magic.  
> > 
> > Good question. To be clear we want a seq lock that goes away on 64b
> > since what it protects is accessed on the fast path (potentially per
> > packet). We could s/u64_stats/u64_seq/ the existing helpers. But that
> > sounds like a lot for a single user. Dunno..  
> 
> It does sound like a lot of a single user.
> 
> And what is the likelihood of this device ever being used on a 32 bit
> system? It is a server class NIC. Are there still 32 bit servers in
> use?
> 
> Maybe "depends on 64BIT" with a good commit message why?

Will this not apply all new MMIO devices? They will either be high
enough class to be only used on 64b systems, or built into a 64b SoC.

No strong feelings either way, but I think we'd need a better defined
guidance on when "depends on 64BIT" is acceptable and when developers
have to go thru the pain of using u64_stats_*.