Staging: speakup: fix read scrolled-back VT

Previously, speakup would always read the non-scrolled part of the VT,
even when the VT is scrolled back with shift-page.  This patch makes
vt.c export screen_pos so that speakup can use it to properly access
the content of the scrolled-back VT.

This was tested with both vgacon and fbcon.

Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
Reviewed-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/speakup/main.c

@@ -264,8 +264,9 @@ static struct notifier_block vt_notifier_block = {
 	.notifier_call = vt_notifier_call,
 };
 
-static unsigned char get_attributes(u16 *pos)
+static unsigned char get_attributes(struct vc_data *vc, u16 *pos)
 {
+	pos = screen_pos(vc, pos - (u16 *)vc->vc_origin, 1);
 	return (u_char) (scr_readw(pos) >> 8);
 }
 
@@ -275,7 +276,7 @@ static void speakup_date(struct vc_data *vc)
 	spk_y = spk_cy = vc->vc_y;
 	spk_pos = spk_cp = vc->vc_pos;
 	spk_old_attr = spk_attr;
-	spk_attr = get_attributes((u_short *) spk_pos);
+	spk_attr = get_attributes(vc, (u_short *)spk_pos);
 }
 
 static void bleep(u_short val)
@@ -469,8 +470,12 @@ static u16 get_char(struct vc_data *vc, u16 *pos, u_char *attribs)
 	u16 ch = ' ';
 
 	if (vc && pos) {
-		u16 w = scr_readw(pos);
-		u16 c = w & 0xff;
+		u16 w;
+		u16 c;
+
+		pos = screen_pos(vc, pos - (u16 *)vc->vc_origin, 1);
+		w = scr_readw(pos);
+		c = w & 0xff;
 
 		if (w & vc->vc_hi_font_mask)
 			c |= 0x100;
@@ -746,7 +751,7 @@ static int get_line(struct vc_data *vc)
 	u_char tmp2;
 
 	spk_old_attr = spk_attr;
-	spk_attr = get_attributes((u_short *) spk_pos);
+	spk_attr = get_attributes(vc, (u_short *)spk_pos);
 	for (i = 0; i < vc->vc_cols; i++) {
 		buf[i] = (u_char) get_char(vc, (u_short *) tmp, &tmp2);
 		tmp += 2;
@@ -811,7 +816,7 @@ static int say_from_to(struct vc_data *vc, u_long from, u_long to,
 	u_short saved_punc_mask = spk_punc_mask;
 
 	spk_old_attr = spk_attr;
-	spk_attr = get_attributes((u_short *) from);
+	spk_attr = get_attributes(vc, (u_short *)from);
 	while (from < to) {
 		buf[i++] = (char)get_char(vc, (u_short *) from, &tmp);
 		from += 2;
@@ -886,7 +891,7 @@ static int get_sentence_buf(struct vc_data *vc, int read_punc)
 	sentmarks[bn][0] = &sentbuf[bn][0];
 	i = 0;
 	spk_old_attr = spk_attr;
-	spk_attr = get_attributes((u_short *) start);
+	spk_attr = get_attributes(vc, (u_short *)start);
 
 	while (start < end) {
 		sentbuf[bn][i] = (char)get_char(vc, (u_short *) start, &tmp);
@@ -1585,7 +1590,7 @@ static int count_highlight_color(struct vc_data *vc)
 		u16 *ptr;
 
 		for (ptr = start; ptr < end; ptr++) {
-			ch = get_attributes(ptr);
+			ch = get_attributes(vc, ptr);
 			bg = (ch & 0x70) >> 4;
 			speakup_console[vc_num]->ht.bgcount[bg]++;
 		}

drivers/tty/vt/vt.c

@@ -4250,6 +4250,7 @@ unsigned short *screen_pos(struct vc_data *vc, int w_offset, int viewed)
 {
 	return screenpos(vc, 2 * w_offset, viewed);
 }
+EXPORT_SYMBOL_GPL(screen_pos);
 
 void getconsxy(struct vc_data *vc, unsigned char *p)
 {