From 4d3153e10e185323ca0d89c4d17b43bdffa803ca Mon Sep 17 00:00:00 2001
From: rumbledethumps <16963588+rumbledethumps@users.noreply.github.com>
Date: Sat, 17 Feb 2024 16:02:57 -0800
Subject: [PATCH] add rp6502 xregn

---
 include/rp6502.h      |  2 ++
 libsrc/rp6502/xregn.c | 19 +++++++++++++++++++
 2 files changed, 21 insertions(+)
 create mode 100644 libsrc/rp6502/xregn.c

diff --git a/include/rp6502.h b/include/rp6502.h
index 53028c35a..7deeebc4c 100644
--- a/include/rp6502.h
+++ b/include/rp6502.h
@@ -117,6 +117,8 @@ long __fastcall__ ria_call_long_errno (unsigned char op);
 
 /* C API for the operating system. */
 
+int __cdecl__ xregn (char device, char channel, unsigned char address, unsigned count,
+    ...);
 int __cdecl__ xreg (char device, char channel, unsigned char address, ...);
 int phi2 (void);
 int codepage (void);
diff --git a/libsrc/rp6502/xregn.c b/libsrc/rp6502/xregn.c
new file mode 100644
index 000000000..ec040be20
--- /dev/null
+++ b/libsrc/rp6502/xregn.c
@@ -0,0 +1,19 @@
+#include <rp6502.h>
+#include <stdarg.h>
+
+int __cdecl__ xregn (char device, char channel, unsigned char address, unsigned count,
+    ...)
+{
+    va_list args;
+    va_start (args, count);
+    RIA.xstack = device;
+    RIA.xstack = channel;
+    RIA.xstack = address;
+    while (count--) {
+        unsigned v = va_arg (args, unsigned);
+        RIA.xstack = v >> 8;
+        RIA.xstack = v;
+    }
+    va_end (args);
+    return ria_call_int_errno (RIA_OP_XREG);
+}