Console-writing code for the new x86 setup code
This implements writing text to the console, including printf().
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/arch/i386/boot/tty.c b/arch/i386/boot/tty.c
new file mode 100644
index 0000000..a8db787
--- /dev/null
+++ b/arch/i386/boot/tty.c
@@ -0,0 +1,112 @@
+/* -*- linux-c -*- ------------------------------------------------------- *
+ *
+ * Copyright (C) 1991, 1992 Linus Torvalds
+ * Copyright 2007 rPath, Inc. - All Rights Reserved
+ *
+ * This file is part of the Linux kernel, and is made available under
+ * the terms of the GNU General Public License version 2.
+ *
+ * ----------------------------------------------------------------------- */
+
+/*
+ * arch/i386/boot/tty.c
+ *
+ * Very simple screen I/O
+ * XXX: Probably should add very simple serial I/O?
+ */
+
+#include "boot.h"
+
+/*
+ * These functions are in .inittext so they can be used to signal
+ * error during initialization.
+ */
+
+void __attribute__((section(".inittext"))) putchar(int ch)
+{
+ unsigned char c = ch;
+
+ if (c == '\n')
+ putchar('\r'); /* \n -> \r\n */
+
+ /* int $0x10 is known to have bugs involving touching registers
+ it shouldn't. Be extra conservative... */
+ asm volatile("pushal; int $0x10; popal"
+ : : "b" (0x0007), "c" (0x0001), "a" (0x0e00|ch));
+}
+
+void __attribute__((section(".inittext"))) puts(const char *str)
+{
+ int n = 0;
+ while (*str) {
+ putchar(*str++);
+ n++;
+ }
+}
+
+/*
+ * Read the CMOS clock through the BIOS, and return the
+ * seconds in BCD.
+ */
+
+static u8 gettime(void)
+{
+ u16 ax = 0x0200;
+ u16 cx, dx;
+
+ asm("int $0x1a"
+ : "+a" (ax), "=c" (cx), "=d" (dx)
+ : : "ebx", "esi", "edi");
+
+ return dx >> 8;
+}
+
+/*
+ * Read from the keyboard
+ */
+int getchar(void)
+{
+ u16 ax = 0;
+ asm("int $0x16" : "+a" (ax));
+
+ return ax & 0xff;
+}
+
+static int kbd_pending(void)
+{
+ u8 pending;
+ asm("int $0x16; setnz %0"
+ : "=rm" (pending)
+ : "a" (0x0100));
+ return pending;
+}
+
+void kbd_flush(void)
+{
+ for (;;) {
+ if (!kbd_pending())
+ break;
+ getchar();
+ }
+}
+
+int getchar_timeout(void)
+{
+ int cnt = 30;
+ int t0, t1;
+
+ t0 = gettime();
+
+ while (cnt) {
+ if (kbd_pending())
+ return getchar();
+
+ t1 = gettime();
+ if (t0 != t1) {
+ cnt--;
+ t0 = t1;
+ }
+ }
+
+ return 0; /* Timeout! */
+}