iflib: Add subinterface interrupt allocation function

[erj]

Summary

The ice(4) driver will add the ability to create extra interfaces
that hang off of the base interface; to do that the driver requires
a method for the subinterface to request hardware interrupt resources
from the base interface. This functionality is planned to be upstreamed to the ice(4) driver soon.

Note: this is part of a stack of patches that also includes whitespace fixes as well as an extra helper function.

[gallatin]

sys/net/iflib.c

2524

Can you explain the move from sctx to scctx here?

7114

As I said on the other review before I noticed it was abandoned: Some whitespace changes snuck in. Please remove them from this functional commit..

[erj]

sys/net/iflib.c

2524

This could've been a separate patch -- but I noticed that both sctx and scctx are referring to the same structure in ctx, so I just changed things to just use one of them. I'm not sure what the original intent for sctx was.

7114

Krzysztof suggested this when I let him review this patch, too. I was worried about how Jeff would apply it if it were more than one patch (that's why it was two but I combined it into one), but the documentation does say that arc patch should automatically pull the predecessors in a patch stack, so maybe that wasn't necessary. I'll pull the whitespace/alignment changes out, anyway.

[erj]

Split changes out into different Differential revisions for easier review

[erj]

@jeffrey.e.pieper_intel.com Applying this revision using "arc patch" should pull all the parent revisions, too, but we'll have to double check to make sure.

sys/net/iflib.c

2524

This change was moved to D41325 to provide more clarity.

7114

I moved non-functional whitespace changes to D41324.

[erj]

Any new thoughts on this review or the previous one in the stack? I'd like to get these in for 14.0-RELEASE.

[kbowling]

@erj can you post the draft driver update, I'd like to see how it intends to use this patch stack before commentary

[erj]

Rebase on latest main; remove whitespace error

[erj]

Update value used for IFLIB_FEATURE_SUB_INTERFACES

[erj]

In D39930#943725, @kbowling wrote:

@erj can you post the draft driver update, I'd like to see how it intends to use this patch stack before commentary

It's very late, but it's here: https://reviews.freebsd.org/D44004. This review and that one are part of the same Phabricator patch stack now.