From 9477c1eb2f7477114b73ba162081a694503170c7 Mon Sep 17 00:00:00 2001
From: David du Colombier <0intro@gmail.com>
Date: Thu, 26 Apr 2001 00:00:00 +0000
Subject: [PATCH] Plan 9 from Bell Labs 2001-04-26

---
 pc/devvga.c | 27 ++++++++++++++++++++++++++-
 pc/screen.h |  1 +
 2 files changed, 27 insertions(+), 1 deletion(-)

diff --git a/pc/devvga.c b/pc/devvga.c
index 67c7af5d1263bf30fc7b11d2c17308a58a620486..0e6bf0b7f0096d21efe4edfdbfb6b1a1dea896c1 100644
--- a/pc/devvga.c
+++ b/pc/devvga.c
@@ -17,10 +17,14 @@
 enum {
 	Qdir,
 	Qvgactl,
+	Qvgaovl,
+	Qvgaovlctl,
 };
 
 static Dirtab vgadir[] = {
-	"vgactl",	{ Qvgactl, 0 },		0,	0660,
+	"vgactl",		{ Qvgactl, 0 },		0,	0660,
+	"vgaovl",		{ Qvgaovl, 0 },		0,	0660,
+	"vgaovlctl",	{ Qvgaovlctl, 0 },	0, 	0660,
 };
 
 static void
@@ -131,6 +135,11 @@ vgaread(Chan* c, void* a, long n, vlong off)
 
 		return n;
 
+	case Qvgaovl:
+	case Qvgaovlctl:
+		error(Ebadusefd);
+		break;
+
 	default:
 		error(Egreg);
 		break;
@@ -337,11 +346,14 @@ vgactl(char* a)
 	error(Ebadarg);
 }
 
+char Enooverlay[] = "No overlay support";
+
 static long
 vgawrite(Chan* c, void* a, long n, vlong off)
 {
 	char *p;
 	ulong offset = off;
+	VGAscr *scr;
 
 	switch(c->qid.path & ~CHDIR){
 
@@ -363,6 +375,19 @@ vgawrite(Chan* c, void* a, long n, vlong off)
 		free(p);
 		return n;
 
+	case Qvgaovl:
+		scr = &vgascreen[0];
+		pprint("vgawrite: Qvgaovl %d (%s)\n", Qvgaovl, scr->dev->name);
+		return 0;
+
+	case Qvgaovlctl:
+		scr = &vgascreen[0];
+		if (scr->dev->ovlctl == nil) {
+			error(Enooverlay);
+			break;
+		}
+		return scr->dev->ovlctl(scr, a, n);
+
 	default:
 		error(Egreg);
 		break;
diff --git a/pc/screen.h b/pc/screen.h
index f1b2ee80ed68adb776aceda823dec95195726a69..64c175e015bb12e696bb266fb7eb8782de4e808a 100644
--- a/pc/screen.h
+++ b/pc/screen.h
@@ -68,6 +68,7 @@ struct VGAdev {
 	ulong	(*linear)(VGAscr*, int*, int*);
 	void	(*drawinit)(VGAscr*);
 	int	(*fill)(VGAscr*, Rectangle, ulong);
+	int	(*ovlctl)(VGAscr*, void*, int);
 };
 
 struct VGAcur {