.\"	$NetBSD: portfeatures.9,v 1.3 2023/03/06 12:25:06 thorpej Exp $
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.Dd March 6, 2023
.Dt PORTFEATURES 9
.Os
.
.Sh NAME
.Nm portfeatures
.Nd the __HAVEs (\|and the have nots\|)
.
.Sh DESCRIPTION
Machine-independent kernel code adapts to differences in hardware
capabilities provided by the machine-dependent parts of the kernel.
A port declares its capabilities by defining various
.Li __HAVE_ Ns Ar feature
macros.
This manual page provides an index of such macros with pointers to
other manual pages in the kernel section that provide all the relevant
details.
.Bl -tag -width Dv
.
.\" ---------
.It Dv __HAVE_MUTEX_STUBS Pq Xr mutex 9
The port provides fast path mutex enter and exit stubs.
.
.\" ---------
.It Dv __HAVE_PREEMPTION Pq Xr cpu_need_resched 9
The port can preempt kernel lwps with
.Dv RESCHED_KPREEMPT .
.
.\" ---------
.It Dv __HAVE_PTRACE_MACHDEP
The port has MD
.Xr ptrace 2
requests, defines
.Dv PTRACE_MACHDEP_REQUEST_CASES
macro with
.Ic case
labels for its MD requests.
.
.\" ---------
.It Dv __HAVE_RAS Pq Xr ras 9
The port supports restartable atomic sequences.
.
.\" ---------
.It Dv __HAVE_SIMPLE_MUTEXES Pq Xr mutex 9
The port provides a CAS function that is either MP-safe, or does not
need to be MP safe.
Adaptive mutexes on these architectures do not require an additional
interlock.
.
.\" ---------
.It Dv __HAVE_SPIN_MUTEX_STUBS Pq Xr mutex 9
The port provides fast path enter and exit stubs for spin mutexes.
.
.\" ---------
.It Dv __HAVE_UCAS_FULL Pq Xr ucas 9
The port provides a full implementation of the low-level primitives
required for atomic compare-and-swap operations to user-space addresses.
.
.\" ---------
.It Dv __HAVE_UCAS_MP Pq Xr ucas 9
The port does not provide a full implementation of the low-level
primitives required for atomic compare-and-swap operations to user-space
addresses, but does provide an implementation of those primitives that
can be used if
.Pq and only if
the system has more than one processor.
.El