[PATCH 1 of 3] xen/vga: Add 'vga_delay' parameter to delay screen output by X miliseconds per line

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

# HG changeset patch
# User Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
# Date 1333398408 14400
# Node ID f1da2ce71ed41d1b74ebe6916ff7710d6579438e
# Parent  1088c8557a46ab28e509bb9482e2a73a21590df8
xen/vga: Add 'vga_delay' parameter to delay screen output by X miliseconds per line.

This is useful if you find yourself on machine that has no serial console,
nor any PCI, PCIe to put in a serial card. Nothing really fancy except it allows
to capture the screenshot of the screen using a camera.

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

diff -r 1088c8557a46 -r f1da2ce71ed4 xen/drivers/video/vga.c
--- a/xen/drivers/video/vga.c	Fri Mar 30 21:05:54 2012 +0100
+++ b/xen/drivers/video/vga.c	Mon Apr 02 16:26:48 2012 -0400
@@ -10,7 +10,7 @@
 #include <xen/mm.h>
 #include <xen/vga.h>
 #include <asm/io.h>
-
+#include <xen/delay.h>
 /* Filled in by arch boot code. */
 struct xen_vga_console_info vga_console_info;
 
@@ -49,6 +49,12 @@ void (*vga_puts)(const char *) = vga_noo
 static char __initdata opt_vga[30] = "";
 string_param("vga", opt_vga);
 
+/*
+ * 'vga_delay=miliseconds' which defines to delay to print a line
+ * to the screen. 2 is a a good value to get a good screen output.
+ */
+unsigned int __read_mostly vga_delay;
+integer_param("vga_delay", vga_delay);
 /* VGA text-mode definitions. */
 static unsigned int columns, lines;
 #define ATTRIBUTE   7
@@ -135,6 +141,9 @@ static void vga_text_puts(const char *s)
                 ypos = lines - 1;
                 memmove(video, video + 2 * columns, ypos * 2 * columns);
                 memset(video + ypos * 2 * columns, 0, 2 * xpos);
+                if (vga_delay)
+                    mdelay(vga_delay);
+
             }
             xpos = 0;
         }