chario: more EOF propagation

Propagate it also from Busy(), which allows to remove it from
the kbd buffer immediately, rather than to leave for next read().
Thus the change in console.asm.

Author: stsp

kernel/chario.c

@@ -106,8 +106,13 @@ STATIC void CharCmd(struct dhdr FAR *pdev, unsigned command)
 
 STATIC int Busy(struct dhdr FAR *pdev)
 {
+  int ret;
+  ____R(CharReqHdr.r_count) = 1;
   CharCmd(pdev, C_ISTAT);
-  return CharReqHdr.r_status & S_BUSY;
+  ret = CharReqHdr.r_status & S_BUSY;
+  if (!ret && !CharReqHdr.r_count)
+    return 256;
+  return ret;
 }
 
 void con_flush(struct dhdr FAR *pdev)
@@ -150,6 +155,8 @@ int ndread(struct dhdr FAR *pdev)
   CharCmd(pdev, C_NDREAD);
   if (CharReqHdr.r_status & S_BUSY)
     return -1;
+  if (!CharReqHdr.r_count)
+    return 256;
   return CharReqHdr.r_ndbyte;
 }
 
@@ -321,13 +328,15 @@ STATIC unsigned do_read_char_dev(struct dhdr FAR *pdev, BOOL check_break)
 
   FOREVER
   {
-    if (!Busy(pdev))
+    if (!(c = Busy(pdev)))
     {
       c = CharIO(pdev, 0, C_INPUT);
       if (c == CTL_C && !check_break && !break_ena)
         clear_break();
       break;
     }
+    if (c == 256)
+      break;
     if (pdev != syscon)
     {
       if (check_break)

kernel/console.asm

@@ -158,8 +158,6 @@ CommonNdRdExit:		; *** tell if key waiting and return its ASCII if yes
 		add     ah,[cs:_kbdType]
                 int     16h                     ; Get status, if zf=0  al=char
                 jz      ConNdRd4                ; Jump if no char available
-                or      ax,ax                   ; See if call was supported
-                jz      _IOSuccess              ; 0 (sometimes) means unsupported
 		call	checke0			; check for e0 scancode
                 or      ax,ax                   ; Zero ?
                 jnz     ConNdRd1                ; Jump if not zero