2 files changed, 225 insertions, 43 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
diff --git a/drivers/video/console/vgacon.c b/drivers/video/console/vgacon.c
index 61894d5bb219..d5a04b68c4d4 100644
--- a/drivers/video/console/vgacon.c
+++ b/drivers/video/console/vgacon.c
@@ -93,7 +93,6 @@ static u8 vgacon_build_attr(struct vc_data *c, u8 color, u8 intensity,
 static void vgacon_invert_region(struct vc_data *c, u16 * p, int count);
 static unsigned long vgacon_uni_pagedir[2];
 
-
 /* Description of the hardware situation */
 static unsigned long    vga_vram_base;          /* Base of video memory */
 static unsigned long    vga_vram_end;           /* End of video memory */
@@ -161,6 +160,201 @@ static inline void write_vga(unsigned char reg, unsigned int val)
         spin_unlock_irqrestore(&vga_lock, flags);
 }
 
+static inline void vga_set_mem_top(struct vc_data *c)
+{
+        write_vga(12, (c->vc_visible_origin - vga_vram_base) / 2);
+}
+
+#ifdef CONFIG_VGACON_SOFT_SCROLLBACK
+#include <linux/bootmem.h>
+/* software scrollback */
+static void *vgacon_scrollback;
+static int vgacon_scrollback_tail;
+static int vgacon_scrollback_size;
+static int vgacon_scrollback_rows;
+static int vgacon_scrollback_cnt;
+static int vgacon_scrollback_cur;
+static int vgacon_scrollback_save;
+static int vgacon_scrollback_restore;
+
+static void vgacon_scrollback_init(int pitch)
+{
+        int rows = CONFIG_VGACON_SOFT_SCROLLBACK_SIZE * 1024/pitch;
+
+        if (vgacon_scrollback) {
+                vgacon_scrollback_cnt  = 0;
+                vgacon_scrollback_tail = 0;
+                vgacon_scrollback_cur  = 0;
+                vgacon_scrollback_rows = rows - 1;
+                vgacon_scrollback_size = rows * pitch;
+        }
+}
+
+static void __init vgacon_scrollback_startup(void)
+{
+        vgacon_scrollback = alloc_bootmem(CONFIG_VGACON_SOFT_SCROLLBACK_SIZE
+                                          * 1024);
+        vgacon_scrollback_init(vga_video_num_columns * 2);
+}
+
+static void vgacon_scrollback_update(struct vc_data *c, int t, int count)
+{
+        void *p;
+
+        if (!vgacon_scrollback_size || c->vc_num != fg_console)
+                return;
+
+        p = (void *) (c->vc_origin + t * c->vc_size_row);
+
+        while (count--) {
+                scr_memcpyw(vgacon_scrollback + vgacon_scrollback_tail,
+                            p, c->vc_size_row);
+                vgacon_scrollback_cnt++;
+                p += c->vc_size_row;
+                vgacon_scrollback_tail += c->vc_size_row;
+
+                if (vgacon_scrollback_tail >= vgacon_scrollback_size)
+                        vgacon_scrollback_tail = 0;
+
+                if (vgacon_scrollback_cnt > vgacon_scrollback_rows)
+                        vgacon_scrollback_cnt = vgacon_scrollback_rows;
+
+                vgacon_scrollback_cur = vgacon_scrollback_cnt;
+        }
+}
+
+static void vgacon_restore_screen(struct vc_data *c)
+{
+        vgacon_scrollback_save = 0;
+
+        if (!vga_is_gfx && !vgacon_scrollback_restore) {
+                scr_memcpyw((u16 *) c->vc_origin, (u16 *) c->vc_screenbuf,
+                            c->vc_screenbuf_size > vga_vram_size ?
+                            vga_vram_size : c->vc_screenbuf_size);
+                vgacon_scrollback_restore = 1;
+                vgacon_scrollback_cur = vgacon_scrollback_cnt;
+        }
+}
+
+static int vgacon_scrolldelta(struct vc_data *c, int lines)
+{
+        int start, end, count, soff, diff;
+        void *d, *s;
+
+        if (!lines) {
+                c->vc_visible_origin = c->vc_origin;
+                vga_set_mem_top(c);
+                return 1;
+        }
+
+        if (!vgacon_scrollback)
+                return 1;
+
+        if (!vgacon_scrollback_save) {
+                vgacon_cursor(c, CM_ERASE);
+                vgacon_save_screen(c);
+                vgacon_scrollback_save = 1;
+        }
+
+        vgacon_scrollback_restore = 0;
+        start = vgacon_scrollback_cur + lines;
+        end = start + abs(lines);
+
+        if (start < 0)
+                start = 0;
+
+        if (start > vgacon_scrollback_cnt)
+                start = vgacon_scrollback_cnt;
+
+        if (end < 0)
+                end = 0;
+
+        if (end > vgacon_scrollback_cnt)
+                end = vgacon_scrollback_cnt;
+
+        vgacon_scrollback_cur = start;
+        count = end - start;
+        soff = vgacon_scrollback_tail - ((vgacon_scrollback_cnt - end) *
+                                         c->vc_size_row);
+        soff -= count * c->vc_size_row;
+
+        if (soff < 0)
+                soff += vgacon_scrollback_size;
+
+        count = vgacon_scrollback_cnt - start;
+
+        if (count > c->vc_rows)
+                count = c->vc_rows;
+
+        diff = c->vc_rows - count;
+
+        d = (void *) c->vc_origin;
+        s = (void *) c->vc_screenbuf;
+
+        while (count--) {
+                scr_memcpyw(d, vgacon_scrollback + soff, c->vc_size_row);
+                d += c->vc_size_row;
+                soff += c->vc_size_row;
+
+                if (soff >= vgacon_scrollback_size)
+                        soff = 0;
+        }
+
+        if (diff == c->vc_rows) {
+                vgacon_cursor(c, CM_MOVE);
+        } else {
+                while (diff--) {
+                        scr_memcpyw(d, s, c->vc_size_row);
+                        d += c->vc_size_row;
+                        s += c->vc_size_row;
+                }
+        }
+
+        return 1;
+}
+#else
+#define vgacon_scrollback_startup(...) do { } while (0)
+#define vgacon_scrollback_init(...)    do { } while (0)
+#define vgacon_scrollback_update(...)  do { } while (0)
+
+static void vgacon_restore_screen(struct vc_data *c)
+{
+        if (c->vc_origin != c->vc_visible_origin)
+                vgacon_scrolldelta(c, 0);
+}
+
+static int vgacon_scrolldelta(struct vc_data *c, int lines)
+{
+        if (!lines)             /* Turn scrollback off */
+                c->vc_visible_origin = c->vc_origin;
+        else {
+                int margin = c->vc_size_row * 4;
+                int ul, we, p, st;
+
+                if (vga_rolled_over >
+                    (c->vc_scr_end - vga_vram_base) + margin) {
+                        ul = c->vc_scr_end - vga_vram_base;
+                        we = vga_rolled_over + c->vc_size_row;
+                } else {
+                        ul = 0;
+                        we = vga_vram_size;
+                }
+                p = (c->vc_visible_origin - vga_vram_base - ul + we) % we +
+                    lines * c->vc_size_row;
+                st = (c->vc_origin - vga_vram_base - ul + we) % we;
+                if (st < 2 * margin)
+                        margin = 0;
+                if (p < margin)
+                        p = 0;
+                if (p > st - margin)
+                        p = st;
+                c->vc_visible_origin = vga_vram_base + (p + ul) % we;
+        }
+        vga_set_mem_top(c);
+        return 1;
+}
+#endif /* CONFIG_VGACON_SOFT_SCROLLBACK */
+
 static const char __init *vgacon_startup(void)
 {
         const char *display_desc = NULL;
@@ -330,7 +524,7 @@ static const char __init *vgacon_startup(void)
 
         vgacon_xres = ORIG_VIDEO_COLS * VGA_FONTWIDTH;
         vgacon_yres = vga_scan_lines;
-
+        vgacon_scrollback_startup();
         return display_desc;
 }
 
@@ -357,11 +551,6 @@ static void vgacon_init(struct vc_data *c, int init)
                 con_set_default_unimap(c);
 }
 
-static inline void vga_set_mem_top(struct vc_data *c)
-{
-        write_vga(12, (c->vc_visible_origin - vga_vram_base) / 2);
-}
-
 static void vgacon_deinit(struct vc_data *c)
 {
         /* When closing the last console, reset video origin */
@@ -455,8 +644,8 @@ static void vgacon_set_cursor_size(int xpos, int from, int to)
 
 static void vgacon_cursor(struct vc_data *c, int mode)
 {
-        if (c->vc_origin != c->vc_visible_origin)
-                vgacon_scrolldelta(c, 0);
+        vgacon_restore_screen(c);
+
         switch (mode) {
         case CM_ERASE:
                 write_vga(14, (c->vc_pos - vga_vram_base) / 2);
@@ -606,6 +795,7 @@ static int vgacon_switch(struct vc_data *c)
                         vgacon_doresize(c, c->vc_cols, c->vc_rows);
         }
 
+        vgacon_scrollback_init(c->vc_size_row);
         return 0;               /* Redrawing not needed */
 }
 
@@ -1073,37 +1263,6 @@ static int vgacon_resize(struct vc_data *c, unsigned int width,
         return 0;
 }
 
-static int vgacon_scrolldelta(struct vc_data *c, int lines)
-{
-        if (!lines)             /* Turn scrollback off */
-                c->vc_visible_origin = c->vc_origin;
-        else {
-                int margin = c->vc_size_row * 4;
-                int ul, we, p, st;
-
-                if (vga_rolled_over >
-                    (c->vc_scr_end - vga_vram_base) + margin) {
-                        ul = c->vc_scr_end - vga_vram_base;
-                        we = vga_rolled_over + c->vc_size_row;
-                } else {
-                        ul = 0;
-                        we = vga_vram_size;
-                }
-                p = (c->vc_visible_origin - vga_vram_base - ul + we) % we +
-                    lines * c->vc_size_row;
-                st = (c->vc_origin - vga_vram_base - ul + we) % we;
-                if (st < 2 * margin)
-                        margin = 0;
-                if (p < margin)
-                        p = 0;
-                if (p > st - margin)
-                        p = st;
-                c->vc_visible_origin = vga_vram_base + (p + ul) % we;
-        }
-        vga_set_mem_top(c);
-        return 1;
-}
-
 static int vgacon_set_origin(struct vc_data *c)
 {
         if (vga_is_gfx ||       /* We don't play origin tricks in graphic modes */
@@ -1146,15 +1305,14 @@ static int vgacon_scroll(struct vc_data *c, int t, int b, int dir,
         if (t || b != c->vc_rows || vga_is_gfx)
                 return 0;
 
-        if (c->vc_origin != c->vc_visible_origin)
-                vgacon_scrolldelta(c, 0);
-
         if (!vga_hardscroll_enabled || lines >= c->vc_rows / 2)
                 return 0;
 
+        vgacon_restore_screen(c);
         oldo = c->vc_origin;
         delta = lines * c->vc_size_row;
         if (dir == SM_UP) {
+                vgacon_scrollback_update(c, t, lines);
                 if (c->vc_scr_end + delta >= vga_vram_end) {
                         scr_memcpyw((u16 *) vga_vram_base,
                                     (u16 *) (oldo + delta),