From 876bdd3153c791a51422a43403143ff10acb6e82 Mon Sep 17 00:00:00 2001
From: Bernd Kuhls <bernd@kuhls.net>
Date: Sat, 3 Jan 2026 15:35:48 +0100
Subject: [PATCH] check for functions inb & outb

Musl C library provides sys/io.h but inb and outb are missing on some
archs. This patch adds a configure check ported from sane-backends:
https://github.com/solanoalves/sane-backend/blob/059b97962ecb1b1ab068f524988d16c5b55bbd29/configure.ac#L314
to fix build errors detected by buildroot autobuilders:
https://autobuild.buildroot.net/results/76d/76d18437241d1281566b76ed1cec2ba99c3532da//build-end.log

./ports_glibc.c: In function 'readPort1':
./ports_glibc.c:54:10: error: implicit declaration of function 'inb' [-Wimplicit-function-declaration]
   54 |   return inb(port);
      |          ^~~
./ports_glibc.c: In function 'writePort1':
./ports_glibc.c:63:3: error: implicit declaration of function 'outb' [-Wimplicit-function-declaration]
   63 |   outb(value, port);
      |   ^~~~

Upstream: https://github.com/brltty/brltty/commit/85cadac951cda709ce53d49923114595c16a8f16

Signed-off-by: Bernd Kuhls <bernd@kuhls.net>
---
 Programs/ports_glibc.c |  4 ++--
 config.h.in            |  3 +++
 configure.ac           | 19 +++++++++++++++++++
 3 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/Programs/ports_glibc.c b/Programs/ports_glibc.c
index 4233f9ea0..4a57f626d 100644
--- a/Programs/ports_glibc.c
+++ b/Programs/ports_glibc.c
@@ -50,7 +50,7 @@ disablePorts (unsigned short int base, unsigned short int count) {
 
 unsigned char
 readPort1 (unsigned short int port) {
-#ifdef HAVE_SYS_IO_H
+#ifdef BRLTTY_HAVE_SYS_IO_H_WITH_INB_OUTB
   return inb(port);
 #else /* HAVE_SYS_IO_H */
   return 0;
@@ -59,7 +59,7 @@ readPort1 (unsigned short int port) {
 
 void
 writePort1 (unsigned short int port, unsigned char value) {
-#ifdef HAVE_SYS_IO_H
+#ifdef BRLTTY_HAVE_SYS_IO_H_WITH_INB_OUTB
   outb(value, port);
 #endif /* HAVE_SYS_IO_H */
 }
diff --git a/config.h.in b/config.h.in
index 537d3af92..edea70cea 100644
--- a/config.h.in
+++ b/config.h.in
@@ -331,6 +331,9 @@ extern "C" {
 /* Define this if the header file sys/io.h exists. */
 #undef HAVE_SYS_IO_H
 
+/* Define to 1 if you have the <sys/io.h> providing inb,outb. */
+#undef BRLTTY_HAVE_SYS_IO_H_WITH_INB_OUTB
+
 /* Define this if the header file sys/modem.h exists. */
 #undef HAVE_SYS_MODEM_H
 
diff --git a/configure.ac b/configure.ac
index b78d482f6..0a2a70dd0 100644
--- a/configure.ac
+++ b/configure.ac
@@ -961,6 +961,25 @@ AC_CHECK_FUNCS([shmget shm_open])
 AC_CHECK_FUNCS([getpeereid getpeerucred getzoneid])
 AC_CHECK_FUNCS([mempcpy wmempcpy])
 
+dnl sys/io.h might provide ioperm but not inb,outb (like for
+dnl non i386/x32/x86_64 with musl libc)
+if test "${ac_cv_header_sys_io_h}" = "yes"; then
+  AC_MSG_CHECKING([for inb,outb (provided by sys/io.h)])
+  AC_LINK_IFELSE(
+    [AC_LANG_PROGRAM([[#include <sys/io.h>]],
+      [[inb(0);outb(0,0);]])],
+    [AC_MSG_RESULT([yes])
+      brltty_cv_have_sys_io_h_with_inb_outb="yes"],
+    [AC_MSG_RESULT([no])
+      brltty_cv_have_sys_io_h_with_inb_outb="no"
+      AC_MSG_WARN([sys/io.h does not provide inb,outb (non i386/x32/x86_64 arch?)])])
+  if test "$brltty_cv_have_sys_io_h_with_inb_outb" = "yes"; then
+    AC_DEFINE(BRLTTY_HAVE_SYS_IO_H_WITH_INB_OUTB, 1, [Define to 1 if you have the <sys/io.h> providing inb,outb.])
+  fi
+else
+  brltty_cv_have_sys_io_h_with_inb_outb="no"
+fi
+
 case "${host_os}"
 in
    cygwin*|mingw*)
-- 
2.47.3