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>

1 files changed, 112 insertions, 0 deletions

diff --git a/arch/i386/boot/tty.c b/arch/i386/boot/tty.c
new file mode 100644
index 000000000000..a8db78736b02
--- /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! */
+}