vgacon: remove software scrollback support

Yunhai Zhang recently fixed a VGA software scrollback bug in commit
ebfdfeeae8c0 ("vgacon: Fix for missing check in scrollback handling"),
but that then made people look more closely at some of this code, and
there were more problems on the vgacon side, but also the fbcon software
scrollback.

We don't really have anybody who maintains this code - probably because
nobody actually _uses_ it any more.  Sure, people still use both VGA and
the framebuffer consoles, but they are no longer the main user
interfaces to the kernel, and haven't been for decades, so these kinds
of extra features end up bitrotting and not really being used.

So rather than try to maintain a likely unused set of code, I'll just
aggressively remove it, and see if anybody even notices.  Maybe there
are people who haven't jumped on the whole GUI badnwagon yet, and think
it's just a fad.  And maybe those people use the scrollback code.

If that turns out to be the case, we can resurrect this again, once
we've found the sucker^Wmaintainer for it who actually uses it.

Reported-by: NopNop Nop <nopitydays@gmail.com>
Tested-by: Willy Tarreau <w@1wt.eu>
Cc: 张云海 <zhangyunhai@nsfocus.com>
Acked-by: Andy Lutomirski <luto@amacapital.net>
Acked-by: Willy Tarreau <w@1wt.eu>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 1 insertions, 220 deletions

diff --git a/drivers/video/console/vgacon.c b/drivers/video/console/vgacon.c
index a52bb3740073..17876f0179b5 100644
--- a/drivers/video/console/vgacon.c
+++ b/drivers/video/console/vgacon.c
@@ -165,214 +165,6 @@ 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
-/* software scrollback */
-struct vgacon_scrollback_info {
-	void *data;
-	int tail;
-	int size;
-	int rows;
-	int cnt;
-	int cur;
-	int save;
-	int restore;
-};
-
-static struct vgacon_scrollback_info *vgacon_scrollback_cur;
-static struct vgacon_scrollback_info vgacon_scrollbacks[MAX_NR_CONSOLES];
-static bool scrollback_persistent = \
-	IS_ENABLED(CONFIG_VGACON_SOFT_SCROLLBACK_PERSISTENT_ENABLE_BY_DEFAULT);
-module_param_named(scrollback_persistent, scrollback_persistent, bool, 0000);
-MODULE_PARM_DESC(scrollback_persistent, "Enable persistent scrollback for all vga consoles");
-
-static void vgacon_scrollback_reset(int vc_num, size_t reset_size)
-{
-	struct vgacon_scrollback_info *scrollback = &vgacon_scrollbacks[vc_num];
-
-	if (scrollback->data && reset_size > 0)
-		memset(scrollback->data, 0, reset_size);
-
-	scrollback->cnt  = 0;
-	scrollback->tail = 0;
-	scrollback->cur  = 0;
-}
-
-static void vgacon_scrollback_init(int vc_num)
-{
-	int pitch = vga_video_num_columns * 2;
-	size_t size = CONFIG_VGACON_SOFT_SCROLLBACK_SIZE * 1024;
-	int rows = size / pitch;
-	void *data;
-
-	data = kmalloc_array(CONFIG_VGACON_SOFT_SCROLLBACK_SIZE, 1024,
-			     GFP_NOWAIT);
-
-	vgacon_scrollbacks[vc_num].data = data;
-	vgacon_scrollback_cur = &vgacon_scrollbacks[vc_num];
-
-	vgacon_scrollback_cur->rows = rows - 1;
-	vgacon_scrollback_cur->size = rows * pitch;
-
-	vgacon_scrollback_reset(vc_num, size);
-}
-
-static void vgacon_scrollback_switch(int vc_num)
-{
-	if (!scrollback_persistent)
-		vc_num = 0;
-
-	if (!vgacon_scrollbacks[vc_num].data) {
-		vgacon_scrollback_init(vc_num);
-	} else {
-		if (scrollback_persistent) {
-			vgacon_scrollback_cur = &vgacon_scrollbacks[vc_num];
-		} else {
-			size_t size = CONFIG_VGACON_SOFT_SCROLLBACK_SIZE * 1024;
-
-			vgacon_scrollback_reset(vc_num, size);
-		}
-	}
-}
-
-static void vgacon_scrollback_startup(void)
-{
-	vgacon_scrollback_cur = &vgacon_scrollbacks[0];
-	vgacon_scrollback_init(0);
-}
-
-static void vgacon_scrollback_update(struct vc_data *c, int t, int count)
-{
-	void *p;
-
-	if (!vgacon_scrollback_cur->data || !vgacon_scrollback_cur->size ||
-	    c->vc_num != fg_console)
-		return;
-
-	p = (void *) (c->vc_origin + t * c->vc_size_row);
-
-	while (count--) {
-		if ((vgacon_scrollback_cur->tail + c->vc_size_row) >
-		    vgacon_scrollback_cur->size)
-			vgacon_scrollback_cur->tail = 0;
-
-		scr_memcpyw(vgacon_scrollback_cur->data +
-			    vgacon_scrollback_cur->tail,
-			    p, c->vc_size_row);
-
-		vgacon_scrollback_cur->cnt++;
-		p += c->vc_size_row;
-		vgacon_scrollback_cur->tail += c->vc_size_row;
-
-		if (vgacon_scrollback_cur->tail >= vgacon_scrollback_cur->size)
-			vgacon_scrollback_cur->tail = 0;
-
-		if (vgacon_scrollback_cur->cnt > vgacon_scrollback_cur->rows)
-			vgacon_scrollback_cur->cnt = vgacon_scrollback_cur->rows;
-
-		vgacon_scrollback_cur->cur = vgacon_scrollback_cur->cnt;
-	}
-}
-
-static void vgacon_restore_screen(struct vc_data *c)
-{
-	c->vc_origin = c->vc_visible_origin;
-	vgacon_scrollback_cur->save = 0;
-
-	if (!vga_is_gfx && !vgacon_scrollback_cur->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_cur->restore = 1;
-		vgacon_scrollback_cur->cur = vgacon_scrollback_cur->cnt;
-	}
-}
-
-static void vgacon_scrolldelta(struct vc_data *c, int lines)
-{
-	int start, end, count, soff;
-
-	if (!lines) {
-		vgacon_restore_screen(c);
-		return;
-	}
-
-	if (!vgacon_scrollback_cur->data)
-		return;
-
-	if (!vgacon_scrollback_cur->save) {
-		vgacon_cursor(c, CM_ERASE);
-		vgacon_save_screen(c);
-		c->vc_origin = (unsigned long)c->vc_screenbuf;
-		vgacon_scrollback_cur->save = 1;
-	}
-
-	vgacon_scrollback_cur->restore = 0;
-	start = vgacon_scrollback_cur->cur + lines;
-	end = start + abs(lines);
-
-	if (start < 0)
-		start = 0;
-
-	if (start > vgacon_scrollback_cur->cnt)
-		start = vgacon_scrollback_cur->cnt;
-
-	if (end < 0)
-		end = 0;
-
-	if (end > vgacon_scrollback_cur->cnt)
-		end = vgacon_scrollback_cur->cnt;
-
-	vgacon_scrollback_cur->cur = start;
-	count = end - start;
-	soff = vgacon_scrollback_cur->tail -
-		((vgacon_scrollback_cur->cnt - end) * c->vc_size_row);
-	soff -= count * c->vc_size_row;
-
-	if (soff < 0)
-		soff += vgacon_scrollback_cur->size;
-
-	count = vgacon_scrollback_cur->cnt - start;
-
-	if (count > c->vc_rows)
-		count = c->vc_rows;
-
-	if (count) {
-		int copysize;
-
-		int diff = c->vc_rows - count;
-		void *d = (void *) c->vc_visible_origin;
-		void *s = (void *) c->vc_screenbuf;
-
-		count *= c->vc_size_row;
-		/* how much memory to end of buffer left? */
-		copysize = min(count, vgacon_scrollback_cur->size - soff);
-		scr_memcpyw(d, vgacon_scrollback_cur->data + soff, copysize);
-		d += copysize;
-		count -= copysize;
-
-		if (count) {
-			scr_memcpyw(d, vgacon_scrollback_cur->data, count);
-			d += count;
-		}
-
-		if (diff)
-			scr_memcpyw(d, s, diff * c->vc_size_row);
-	} else
-		vgacon_cursor(c, CM_MOVE);
-}
-
-static void vgacon_flush_scrollback(struct vc_data *c)
-{
-	size_t size = CONFIG_VGACON_SOFT_SCROLLBACK_SIZE * 1024;
-
-	vgacon_scrollback_reset(c->vc_num, size);
-}
-#else
-#define vgacon_scrollback_startup(...) do { } while (0)
-#define vgacon_scrollback_init(...)    do { } while (0)
-#define vgacon_scrollback_update(...)  do { } while (0)
-#define vgacon_scrollback_switch(...)  do { } while (0)
-
 static void vgacon_restore_screen(struct vc_data *c)
 {
 	if (c->vc_origin != c->vc_visible_origin)
@@ -386,11 +178,6 @@ static void vgacon_scrolldelta(struct vc_data *c, int lines)
 	vga_set_mem_top(c);
 }
 
-static void vgacon_flush_scrollback(struct vc_data *c)
-{
-}
-#endif /* CONFIG_VGACON_SOFT_SCROLLBACK */
-
 static const char *vgacon_startup(void)
 {
 	const char *display_desc = NULL;
@@ -573,10 +360,7 @@ static const char *vgacon_startup(void)
 	vgacon_xres = screen_info.orig_video_cols * VGA_FONTWIDTH;
 	vgacon_yres = vga_scan_lines;
 
-	if (!vga_init_done) {
-		vgacon_scrollback_startup();
-		vga_init_done = true;
-	}
+	vga_init_done = true;
 
 	return display_desc;
 }
@@ -869,7 +653,6 @@ static int vgacon_switch(struct vc_data *c)
 			vgacon_doresize(c, c->vc_cols, c->vc_rows);
 	}
 
-	vgacon_scrollback_switch(c->vc_num);
 	return 0;		/* Redrawing not needed */
 }
 
@@ -1386,7 +1169,6 @@ static bool vgacon_scroll(struct vc_data *c, unsigned int t, unsigned int b,
 	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),
@@ -1450,7 +1232,6 @@ const struct consw vga_con = {
 	.con_save_screen = vgacon_save_screen,
 	.con_build_attr = vgacon_build_attr,
 	.con_invert_region = vgacon_invert_region,
-	.con_flush_scrollback = vgacon_flush_scrollback,
 };
 EXPORT_SYMBOL(vga_con);