sam: fix crash with esc-J on the bottom line

diff --git a/Kernel/platform-sam/README b/Kernel/platform-sam/README
index 8c8d115..a691123 100644 (file)
--- a/Kernel/platform-sam/README
+++ b/Kernel/platform-sam/README
@@ -106,3 +106,4 @@ DONE        -       RTC driver
 DONE   -       Mouse/Joystick/Input
 DONE   -       Review and test signal handling paths more (catching signals
                path appears to be broken)
+DONE   -       Esc-J crashes the console driver

diff --git a/Kernel/platform-sam/sam_vt.s b/Kernel/platform-sam/sam_vt.s
index d681195..3728eee 100644 (file)
--- a/Kernel/platform-sam/sam_vt.s
+++ b/Kernel/platform-sam/sam_vt.s
@@ -164,6 +164,8 @@ _clear_lines:
        push de
        push hl
        ld a,d                  ; count (0-23)
+       or a
+       ret z                   ; zero count is possible - do nothing
        ld d,#0
        ; Now how much to copy ?
        ; 128 bytes per scan line, 8 scan lines per char = 1024