vgabios: Add software cursor capability

Add mechanism for drawing a cursor to the framebuffer to implement a
cursor in software.  The timer interrupt is "hooked" so that the
cursor can blink.  This can be useful for "coreboot native vga".

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

1 files changed, 34 insertions, 0 deletions

diff --git a/vgasrc/vgainit.c b/vgasrc/vgainit.c
index 6ef19e1d..8d122618 100644
--- a/vgasrc/vgainit.c
+++ b/vgasrc/vgainit.c
@@ -88,6 +88,38 @@ allocate_extra_stack(void)
 
 
 /****************************************************************
+ * Timer hook
+ ****************************************************************/
+
+struct segoff_s Timer_Hook_Resume VAR16 VISIBLE16;
+
+void VISIBLE16
+handle_timer_hook(void)
+{
+    if (!vga_emulate_text())
+        return;
+    vgafb_set_swcursor(GET_BDA(timer_counter) % 18 < 9);
+}
+
+static void
+hook_timer_irq(void)
+{
+    if (!CONFIG_VGA_EMULATE_TEXT)
+        return;
+    extern void entry_timer_hook(void);
+    extern void entry_timer_hook_extrastack(void);
+    struct segoff_s oldirq = GET_IVT(0x08);
+    struct segoff_s newirq = SEGOFF(get_global_seg(), (u32)entry_timer_hook);
+    if (CONFIG_VGA_ALLOCATE_EXTRA_STACK && GET_GLOBAL(ExtraStackSeg))
+        newirq = SEGOFF(get_global_seg(), (u32)entry_timer_hook_extrastack);
+    dprintf(1, "Hooking hardware timer irq (old=%x new=%x)\n"
+            , oldirq.segoff, newirq.segoff);
+    SET_VGA(Timer_Hook_Resume, oldirq);
+    SET_IVT(0x08, newirq);
+}
+
+
+/****************************************************************
  * VGA post
  ****************************************************************/
 
@@ -150,6 +182,8 @@ vga_post(struct bregs *regs)
 
     allocate_extra_stack();
 
+    hook_timer_irq();
+
     SET_VGA(HaveRunInit, 1);
 
     // Fixup checksum