x86, setup: Early-boot serial I/O support

This patch adds serial I/O support to the real-mode setup (very early
boot) printf(). It's useful for debugging boot code when running Linux
under KVM, for example. The actual code was lifted from early printk.

Cc: Cyrill Gorcunov <gorcunov@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
LKML-Reference: <1278835617-11368-1-git-send-email-penberg@cs.helsinki.fi>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

1 files changed, 41 insertions, 0 deletions

diff --git a/arch/x86/boot/string.c b/arch/x86/boot/string.c
index f94b7a0c2abf..aba29df4a7bb 100644
--- a/arch/x86/boot/string.c
+++ b/arch/x86/boot/string.c
@@ -30,6 +30,22 @@ int strcmp(const char *str1, const char *str2)
         return 0;
 }
 
+int strncmp(const char *cs, const char *ct, size_t count)
+{
+        unsigned char c1, c2;
+
+        while (count) {
+                c1 = *cs++;
+                c2 = *ct++;
+                if (c1 != c2)
+                        return c1 < c2 ? -1 : 1;
+                if (!c1)
+                        break;
+                count--;
+        }
+        return 0;
+}
+
 size_t strnlen(const char *s, size_t maxlen)
 {
         const char *es = s;
@@ -48,3 +64,28 @@ unsigned int atou(const char *s)
                 i = i * 10 + (*s++ - '0');
         return i;
 }
+
+/* Works only for digits and letters, but small and fast */
+#define TOLOWER(x) ((x) | 0x20)
+
+unsigned long long simple_strtoull(const char *cp, char **endp, unsigned int base)
+{
+        unsigned long long result = 0;
+
+        if (base == 16 && cp[0] == '0' && TOLOWER(cp[1]) == 'x')
+                cp += 2;
+
+        while (isxdigit(*cp)) {
+                unsigned int value;
+
+                value = isdigit(*cp) ? *cp - '0' : TOLOWER(*cp) - 'a' + 10;
+                if (value >= base)
+                        break;
+                result = result * base + value;
+                cp++;
+        }
+        if (endp)
+                *endp = (char *)cp;
+
+        return result;
+}