Serial debugging code must not access BDA.

Regular serial writing code uses the system timer to timeout failed
    writes - however, serial debugging can't rely on access to the BDA
    segment or the hardware timer.
Therefore, implement a simple debug only serial writing function and
    separate it from the regular serial output code.
Also include change to dump_regs - don't call __dprintf if debugging
    not on.

1 files changed, 10 insertions, 39 deletions

diff --git a/src/serial.c b/src/serial.c
index 026c399..f9988a3 100644
--- a/src/serial.c
+++ b/src/serial.c
@@ -76,10 +76,15 @@ handle_1400(struct bregs *regs)
     set_success(regs);
 }
 
-static int
-write_serial(u16 addr, u16 timeout, char c)
+// SERIAL - WRITE CHARACTER TO PORT
+static void
+handle_1401(struct bregs *regs)
 {
+    u16 addr = getComAddr(regs);
+    if (!addr)
+        return;
     u16 timer = GET_BDA(timer_counter);
+    u16 timeout = GET_BDA(com_timeout[regs->dx]);
     while (((inb(addr+5) & 0x60) != 0x60) && (timeout)) {
         u16 val16 = GET_BDA(timer_counter);
         if (val16 != timer) {
@@ -87,24 +92,10 @@ write_serial(u16 addr, u16 timeout, char c)
             timeout--;
         }
     }
-    if (!timeout)
-        // Ran out of time.
-        return -1;
-    outb(c, addr);
-    return 0;
-}
-
-// SERIAL - WRITE CHARACTER TO PORT
-static void
-handle_1401(struct bregs *regs)
-{
-    u16 addr = getComAddr(regs);
-    if (!addr)
-        return;
-    u16 timeout = GET_BDA(com_timeout[regs->dx]);
-    int ret = write_serial(addr, timeout, regs->al);
+    if (timeout)
+        outb(regs->al, addr);
     regs->ah = inb(addr+5);
-    if (ret)
+    if (!timeout)
         regs->ah |= 0x80;
     set_success(regs);
 }
@@ -172,26 +163,6 @@ handle_14(struct bregs *regs)
 
 
 /****************************************************************
- * Serial debugging
- ****************************************************************/
-
-#define BX_DEBUG_PORT 0x03f8
-
-void
-debug_serial_setup()
-{
-    /* setup for serial logging: 8N1 */
-    outb(0x03, BX_DEBUG_PORT+3);
-}
-
-void
-debug_serial(char c)
-{
-    write_serial(BX_DEBUG_PORT, 0x0a, c);
-}
-
-
-/****************************************************************
  * LPT ports
  ****************************************************************/