From 5bb49da24645f70fe733a106f21ca5a1987c74a5 Mon Sep 17 00:00:00 2001
From: Paul Mathieu <paul@ponteilla.net>
Date: Fri, 3 Oct 2025 23:27:27 +0200
Subject: [PATCH] polio: fix comms

---
 src/paracomm.c   | 19 ++++---------------
 src/paracomm.h   |  9 +++------
 src/polio-main.c | 38 ++++++++++++++++++++++++++++----------
 src/polio.s      | 13 ++++++-------
 4 files changed, 41 insertions(+), 38 deletions(-)

diff --git a/src/paracomm.c b/src/paracomm.c
index 88a1493..bebeb8f 100644
--- a/src/paracomm.c
+++ b/src/paracomm.c
@@ -22,6 +22,7 @@ static uint8_t miso_recvbuf[256];
 static uint8_t miso_size;
 static uint8_t miso_received_nibbles;
 static uint8_t miso_state;
+recv_cb miso_recv_cb;
 
 static void swapbuffers() {
     mosi_sendbuf = mosi_workbuf[mosi_workbuf_idx];
@@ -92,19 +93,21 @@ void paracomm_feed(uint8_t n) {
         miso_received_nibbles += 1;
 
         if (miso_received_nibbles == 2 * miso_size) {
+            miso_recv_cb(miso_recvbuf, miso_size);
             miso_state = 0;
         }
     } break;
     }
 }
 
-void paracomm_init() {
+void paracomm_init(recv_cb miso_cb) {
     mosi_size = 0;
     mosi_workbuf_idx = 0;
     mosi_workbuf_size = 0;
     mosi_state = 0;
 
     miso_state = 0;
+    miso_recv_cb = miso_cb;
 }
 
 int paracomm_send(uint8_t b) {
@@ -119,20 +122,6 @@ int paracomm_send(uint8_t b) {
     return 0;
 }
 
-uint8_t paracomm_recv(uint8_t* buf, uint8_t size) {
-    if (miso_state != 0) {
-        return 0;
-    }
-    if (size > miso_size) {
-        size = miso_size;
-    }
-    memcpy(buf, miso_recvbuf, size);
-    memcpy(miso_recvbuf, miso_recvbuf+size, miso_size - size);
-    miso_size -= size;
-
-    return size;
-}
-
 uint8_t paracomm_busy() {
     return mosi_state != 0 || miso_state != 0;
 }
diff --git a/src/paracomm.h b/src/paracomm.h
index 4b5930c..30ada4e 100644
--- a/src/paracomm.h
+++ b/src/paracomm.h
@@ -2,19 +2,16 @@
 
 #include <stdint.h>
 
+typedef void (*recv_cb)(const uint8_t* buf, uint8_t size);
+
 /** Must call first **/
-void paracomm_init();
+void paracomm_init(recv_cb cb);
 
 /** Sends a single byte.
  * Returns: 0 if no error, non-0 otherwise.
  */
 int paracomm_send(uint8_t b);
 
-/** Receive some bytes.
- * Returns: number of bytes copied
- */
-uint8_t paracomm_recv(uint8_t* buf, uint8_t size);
-
 /** Call after reading a nibble from the port */
 void paracomm_feed(uint8_t n);
 
diff --git a/src/polio-main.c b/src/polio-main.c
index d94a186..225b5e8 100644
--- a/src/polio-main.c
+++ b/src/polio-main.c
@@ -12,7 +12,7 @@
 #define kParallelDataPort 0x3bc
 #define kParallelStatusPort 0x3bd
 #define kParallelControlPort 0x3be
-#define kParaDelay 400
+#define kParaDelay 100
 #define kRecvBufferSize 256
 
 void dosdbt();
@@ -51,15 +51,16 @@ static void __delay__(int n) {
     }
 }
 
-uint8_t xferpara() {
-    uint8_t mosib = paracomm_nextbyte();
-    __outb__(kParallelDataPort, mosib);
-    __outb__(kParallelControlPort, 1);
-    __delay__(kParaDelay);
-    __outb__(kParallelControlPort, 0);
-    __delay__(kParaDelay);
-    uint8_t mison = __inb__(kParallelStatusPort) >> 4;
-    paracomm_feed(mison);
+uint8_t xferpara(uint8_t until_idle) {
+    do {
+        uint8_t mosib = paracomm_nextbyte();
+        __outb__(kParallelDataPort, mosib);
+        __outb__(kParallelControlPort, 1);
+        __delay__(kParaDelay);
+        __outb__(kParallelControlPort, 0);
+        uint8_t mison = __inb__(kParallelStatusPort) >> 4;
+        paracomm_feed(mison);
+    } while (until_idle && paracomm_busy());
 
     return paracomm_busy();
 }
@@ -74,6 +75,23 @@ uint8_t parasend(uint8_t* addr, uint8_t size) {
     return i;
 }
 
+uint8_t pararecv(uint8_t* buf, uint8_t size) {
+    if (parasize == 0) {
+        return 0;
+    }
+    if (size > parasize) {
+        size = parasize;
+    }
+    memcpy(buf, parabuf, size);
+    if (size < parasize) {
+        memcpy(parabuf, parabuf+size, parasize - size);
+    }
+    parasize -= size;
+
+    return size;
+}
+
+
 int main() {
     dosdbt();
     parasize = 0;
diff --git a/src/polio.s b/src/polio.s
index 6865d11..723d976 100644
--- a/src/polio.s
+++ b/src/polio.s
@@ -6,7 +6,7 @@
     .global _start
 _start:
     cli
-    mov ax, 0x2000      # stack address
+    mov ax, 0x2000      # stack address, shared with polmon
     mov sp, ax          # ss should already be 0
     sti
     jmp main
@@ -143,7 +143,7 @@ recvpara:
     mov ax, [bp+0]
     add ax, si
     mov dx, [bp+2]
-    call paracomm_recv
+    call pararecv
     ret
 
     .section .text.int80h
@@ -157,12 +157,11 @@ int80h:
     xor cx, cx
     mov es, cx
     mov ds, cx
-    shl ah
-    cmp ah, offset int80h_entries
+    xchg ah, cl
+    shl cl
+    cmp cl, offset int80h_entries
     jge 0f
-    mov al, ah
-    xor ah, ah
-    mov si, ax
+    mov si, cx
     mov bp, sp
     lea bp, [bp + 16]       # 10 for us, 6 for the interrupt
     call cs:[int80h_table+si]