[PATCH] vgacon: Add support for soft scrollback

The scrollback buffer of the VGA console is located in VGA RAM.  This RAM
is fixed in size and is very small.  To make the scrollback buffer larger,
it must be placed instead in System RAM.

This patch adds this feature.  The feature and the size of the buffer are
made as a kernel config option.  Besides consuming kernel memory, this
feature will slow down the console by approximately 20%.

Signed-off-by: Antonino Daplas <adaplas@pol.net>
Signed-off-by: Jiri Slaby <jirislaby@gmail.com>
Cc: Jindrich Makovicka <makovick@kmlinux.fjfi.cvut.cz>
Cc: Martin Mares <mj@ucw.cz>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 24 insertions, 0 deletions

diff --git a/drivers/video/console/Kconfig b/drivers/video/console/Kconfig
index 6ee449858a5c..4444bef68fba 100644
--- a/drivers/video/console/Kconfig
+++ b/drivers/video/console/Kconfig
@@ -26,6 +26,30 @@ config VGA_CONSOLE
 #          fi
 #       fi
 
+config VGACON_SOFT_SCROLLBACK
+       bool "Enable Scrollback Buffer in System RAM"
+       depends on VGA_CONSOLE
+       default n
+       help
+         The scrollback buffer of the standard VGA console is located in
+         the VGA RAM.  The size of this RAM is fixed and is quite small.
+         If you require a larger scrollback buffer, this can be placed in
+         System RAM which is dynamically allocated during intialization.
+         Placing the scrollback buffer in System RAM will slightly slow
+         down the console.
+
+         If you want this feature, say 'Y' here and enter the amount of
+         RAM to allocate for this buffer.  If unsure, say 'N'.
+
+config VGACON_SOFT_SCROLLBACK_SIZE
+       int "Scrollback Buffer Size (in KB)"
+       depends on VGACON_SOFT_SCROLLBACK
+       default "64"
+       help
+         Enter the amount of System RAM to allocate for the scrollback
+         buffer.  Each 64KB will give you approximately 16 80x25
+         screenfuls of scrollback buffer
+
 config VIDEO_SELECT
         bool "Video mode selection support"
         depends on  X86 && VGA_CONSOLE