bus: Document special ranges of IVARs
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Authored by jhb on Tue, Dec 9, 8:35 PM.

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imp
andrew
manu

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Summary

Some IVAR indices are special in that they have global meaning across
multiple buses where as other IVARs are always private to the local bus.
Try to document this a bit and add constants for the various ranges to
avoid future conflicts.

This is mostly a no-op except for some buses that started their IVAR
indices at 1 instead of 0. Those buses now start at 0 after this
change. Also, IVAR indices are now generally defined as enum's as
that makes it easier to define them.

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rG FreeBSD src repository

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Buildable 69156
Build 66039: arc lint + arc unit

Event Timeline

jhb created this revision.Tue, Dec 9, 8:35 PM

Owners added a reviewer: Restricted Owners Package.Tue, Dec 9, 8:35 PM

Herald added a reviewer: andrew. · View Herald TranscriptTue, Dec 9, 8:35 PM

Herald added a reviewer: andrew. · View Herald Transcript

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jhb requested review of this revision.Tue, Dec 9, 8:35 PM

Harbormaster completed remote builds in B69156: Diff 167801.Tue, Dec 9, 8:35 PM

jhb added a child revision: D54160: bus: Drop a couple of unused IVAR indices.Tue, Dec 9, 8:35 PM

jhb added a parent revision: D54155: acpi_gpiobus: Reuse the existing IVAR index for an ACPI handle.Tue, Dec 9, 8:35 PM

andrew added inline comments.Wed, Dec 10, 2:01 PM

sys/arm64/arm64/gic_v3_var.h
114	Are you planning on MFCing this change? If not then we could just drop them.
sys/sys/bus.h
312	I don't think this is needed, the GICv3 ivars can be in the private space.

jhb added inline comments.Wed, Dec 10, 4:19 PM

sys/arm64/arm64/gic_v3_var.h
114	I might MFC this change but have a followup change that can't be merged that drops unused ivars.
sys/sys/bus.h
312	I was going to ask about these as followups. For now I just want to document what is there. Can the regular GIC IVARs also be in the private space?

andrew added inline comments.Wed, Dec 10, 5:10 PM

sys/arm64/arm64/gic_v3_var.h
114	It's unused from 13 so you could name it `GICV3_IVAR_UNUSED` to make it self documenting. Wouldn't it be an issue for a MFC renumbering the 1-indexed ivars to be 0-indexed?
sys/sys/bus.h
312	The regular GIC IVARs are shared between the two GIC drivers so can't be in the private space. If you keep it then the name should be `BUS_IVARS_GICV3`. I'll have a GICv5 driver in the next few weeks, but that can use the private space.

jhb added inline comments.Thu, Dec 11, 5:33 PM

sys/arm64/arm64/gic_v3_var.h
114	Oh, yes, so perhaps I won't MFC after all. Still, I think removing the unused entries as a separate commit is easier to review, etc.
sys/sys/bus.h
312	Have you considered just having a single set of GIC IVARs shared by all the drivers btw?