+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 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 *vgacon_startup(void)