rasops: implement scrollback for inteldrm and efifb

[joshua stein-3]

Index: arch/amd64/amd64/efifb.c
===================================================================
RCS file: /cvs/src/sys/arch/amd64/amd64/efifb.c,v
retrieving revision 1.12
diff -u -p -u -p -r1.12 efifb.c
--- arch/amd64/amd64/efifb.c 28 Oct 2017 01:48:03 -0000 1.12
+++ arch/amd64/amd64/efifb.c 16 Apr 2018 15:40:22 -0000
@@ -101,6 +101,7 @@ int efifb_show_screen(void *, void *, i
     void *);
 int efifb_list_font(void *, struct wsdisplay_font *);
 int efifb_load_font(void *, void *, struct wsdisplay_font *);
+void efifb_scrollback(void *, void *, int lines);
 void efifb_efiinfo_init(struct efifb *);
 void efifb_cnattach_common(void);
 
@@ -133,7 +134,8 @@ struct wsdisplay_accessops efifb_accesso
  .free_screen = efifb_free_screen,
  .show_screen = efifb_show_screen,
  .load_font = efifb_load_font,
- .list_font = efifb_list_font
+ .list_font = efifb_list_font,
+ .scrollback = efifb_scrollback,
 };
 
 struct cfdriver efifb_cd = {
@@ -397,6 +399,15 @@ efifb_list_font(void *v, struct wsdispla
  struct rasops_info *ri = &sc->sc_fb->rinfo;
 
  return (rasops_list_font(ri, font));
+}
+
+void
+efifb_scrollback(void *v, void *cookie, int lines)
+{
+ struct efifb_softc *sc = v;
+ struct rasops_info *ri = &sc->sc_fb->rinfo;
+
+ rasops_scrollback(ri, cookie, lines);
 }
 
 int
Index: dev/rasops/rasops.c
===================================================================
RCS file: /cvs/src/sys/dev/rasops/rasops.c,v
retrieving revision 1.50
diff -u -p -u -p -r1.50 rasops.c
--- dev/rasops/rasops.c 23 Jan 2018 10:10:32 -0000 1.50
+++ dev/rasops/rasops.c 16 Apr 2018 15:40:22 -0000
@@ -1373,8 +1373,13 @@ struct rasops_screen {
  int rs_visible;
  int rs_crow;
  int rs_ccol;
+
+ int rs_dispoffset; /* rs_bs index, start of our actual screen */
+ int rs_visibleoffset; /* rs_bs index, current scrollback screen */
 };
 
+#define RS_SCROLLBACK_SCREENS 5
+
 int
 rasops_alloc_screen(void *v, void **cookiep,
     int *curxp, int *curyp, long *attrp)
@@ -1387,13 +1392,15 @@ rasops_alloc_screen(void *v, void **cook
  if (scr == NULL)
  return (ENOMEM);
 
- scr->rs_bs = mallocarray(ri->ri_rows,
+ scr->rs_bs = mallocarray(ri->ri_rows * RS_SCROLLBACK_SCREENS,
     ri->ri_cols * sizeof(struct wsdisplay_charcell), M_DEVBUF,
     M_NOWAIT);
  if (scr->rs_bs == NULL) {
  free(scr, M_DEVBUF, sizeof(*scr));
  return (ENOMEM);
  }
+ scr->rs_visibleoffset = scr->rs_dispoffset = ri->ri_rows *
+    (RS_SCROLLBACK_SCREENS - 1) * ri->ri_cols;
 
  *cookiep = scr;
  *curxp = 0;
@@ -1405,13 +1412,19 @@ rasops_alloc_screen(void *v, void **cook
  scr->rs_crow = -1;
  scr->rs_ccol = -1;
 
+ for (i = 0; i < scr->rs_dispoffset; i++) {
+ scr->rs_bs[i].uc = ' ';
+ scr->rs_bs[i].attr = *attrp;
+ }
+
  if (ri->ri_bs && scr->rs_visible) {
- memcpy(scr->rs_bs, ri->ri_bs, ri->ri_rows * ri->ri_cols *
+ memcpy(scr->rs_bs + scr->rs_dispoffset, ri->ri_bs,
+    ri->ri_rows * ri->ri_cols *
     sizeof(struct wsdisplay_charcell));
  } else {
  for (i = 0; i < ri->ri_rows * ri->ri_cols; i++) {
- scr->rs_bs[i].uc = ' ';
- scr->rs_bs[i].attr = *attrp;
+ scr->rs_bs[scr->rs_dispoffset + i].uc = ' ';
+ scr->rs_bs[scr->rs_dispoffset + i].attr = *attrp;
  }
  }
 
@@ -1431,7 +1444,8 @@ rasops_free_screen(void *v, void *cookie
  ri->ri_nscreens--;
 
  free(scr->rs_bs, M_DEVBUF,
-    ri->ri_rows * ri->ri_cols * sizeof(struct wsdisplay_charcell));
+    ri->ri_rows * RS_SCROLLBACK_SCREENS * ri->ri_cols *
+    sizeof(struct wsdisplay_charcell));
  free(scr, M_DEVBUF, sizeof(*scr));
 }
 
@@ -1467,9 +1481,11 @@ rasops_doswitch(void *v)
  ri->ri_eraserows(ri, 0, ri->ri_rows, attr);
  ri->ri_active = scr;
  ri->ri_active->rs_visible = 1;
+ ri->ri_active->rs_visibleoffset = ri->ri_active->rs_dispoffset;
  for (row = 0; row < ri->ri_rows; row++) {
  for (col = 0; col < ri->ri_cols; col++) {
- int off = row * scr->rs_ri->ri_cols + col;
+ int off = row * scr->rs_ri->ri_cols + col +
+    scr->rs_visibleoffset;
 
  ri->ri_putchar(ri, row, col, scr->rs_bs[off].uc,
     scr->rs_bs[off].attr);
@@ -1491,7 +1507,7 @@ rasops_getchar(void *v, int row, int col
  if (scr == NULL || scr->rs_bs == NULL)
  return (1);
 
- *cell = scr->rs_bs[row * ri->ri_cols + col];
+ *cell = scr->rs_bs[row * ri->ri_cols + col + scr->rs_dispoffset];
  return (0);
 }
 
@@ -1521,7 +1537,10 @@ int
 rasops_vcons_putchar(void *cookie, int row, int col, u_int uc, long attr)
 {
  struct rasops_screen *scr = cookie;
- int off = row * scr->rs_ri->ri_cols + col;
+ int off = row * scr->rs_ri->ri_cols + col + scr->rs_dispoffset;
+
+ if (scr->rs_visible && scr->rs_visibleoffset != scr->rs_dispoffset)
+ rasops_scrollback(scr->rs_ri, scr, 0);
 
  scr->rs_bs[off].uc = uc;
  scr->rs_bs[off].attr = attr;
@@ -1540,7 +1559,8 @@ rasops_vcons_copycols(void *cookie, int
  int cols = scr->rs_ri->ri_cols;
  int col, rc;
 
- memmove(&scr->rs_bs[row * cols + dst], &scr->rs_bs[row * cols + src],
+ memmove(&scr->rs_bs[row * cols + dst + scr->rs_dispoffset],
+    &scr->rs_bs[row * cols + src + scr->rs_dispoffset],
     num * sizeof(struct wsdisplay_charcell));
 
  if (!scr->rs_visible)
@@ -1550,7 +1570,7 @@ rasops_vcons_copycols(void *cookie, int
  return ri->ri_copycols(ri, row, src, dst, num);
 
  for (col = dst; col < dst + num; col++) {
- int off = row * cols + col;
+ int off = row * cols + col + scr->rs_dispoffset;
 
  rc = ri->ri_putchar(ri, row, col,
     scr->rs_bs[off].uc, scr->rs_bs[off].attr);
@@ -1569,7 +1589,7 @@ rasops_vcons_erasecols(void *cookie, int
  int i;
 
  for (i = 0; i < num; i++) {
- int off = row * cols + col + i;
+ int off = row * cols + col + i + scr->rs_dispoffset;
 
  scr->rs_bs[off].uc = ' ';
  scr->rs_bs[off].attr = attr;
@@ -1589,8 +1609,15 @@ rasops_vcons_copyrows(void *cookie, int
  int cols = ri->ri_cols;
  int row, col, rc;
 
- memmove(&scr->rs_bs[dst * cols], &scr->rs_bs[src * cols],
-    num * cols * sizeof(struct wsdisplay_charcell));
+ if (dst == 0 && (src + num == ri->ri_rows))
+ memmove(&scr->rs_bs[dst],
+    &scr->rs_bs[src * cols],
+    ((ri->ri_rows * RS_SCROLLBACK_SCREENS * cols) -
+    (src * cols)) * sizeof(struct wsdisplay_charcell));
+ else
+ memmove(&scr->rs_bs[dst * cols + scr->rs_dispoffset],
+    &scr->rs_bs[src * cols + scr->rs_dispoffset],
+    num * cols * sizeof(struct wsdisplay_charcell));
 
  if (!scr->rs_visible)
  return 0;
@@ -1600,7 +1627,7 @@ rasops_vcons_copyrows(void *cookie, int
 
  for (row = dst; row < dst + num; row++) {
  for (col = 0; col < cols; col++) {
- int off = row * cols + col;
+ int off = row * cols + col + scr->rs_dispoffset;
 
  rc = ri->ri_putchar(ri, row, col,
     scr->rs_bs[off].uc, scr->rs_bs[off].attr);
@@ -1620,7 +1647,7 @@ rasops_vcons_eraserows(void *cookie, int
  int i;
 
  for (i = 0; i < num * cols; i++) {
- int off = row * cols + i;
+ int off = row * cols + i + scr->rs_dispoffset;
 
  scr->rs_bs[off].uc = ' ';
  scr->rs_bs[off].attr = attr;
@@ -1871,4 +1898,46 @@ rasops_list_font(void *v, struct wsdispl
  font->index = idx;
  font->cookie = font->data = NULL; /* don't leak kernel pointers */
  return 0;
+}
+
+void
+rasops_scrollback(void *v, void *cookie, int lines)
+{
+ struct rasops_info *ri = v;
+ struct rasops_screen *scr = cookie;
+ int row, col, oldvoff;
+ long attr;
+
+ oldvoff = scr->rs_visibleoffset;
+
+ if (lines == 0)
+ scr->rs_visibleoffset = scr->rs_dispoffset;
+ else {
+ int off = scr->rs_visibleoffset + (lines * ri->ri_cols);
+
+ if (off < 0)
+ off = 0;
+ else if (off > scr->rs_dispoffset)
+ off = scr->rs_dispoffset;
+
+ scr->rs_visibleoffset = off;
+ }
+
+ if (scr->rs_visibleoffset == oldvoff)
+ return;
+
+ rasops_cursor(ri, 0, 0, 0);
+ ri->ri_eraserows(ri, 0, ri->ri_rows, attr);
+ for (row = 0; row < ri->ri_rows; row++) {
+ for (col = 0; col < ri->ri_cols; col++) {
+ int off = row * scr->rs_ri->ri_cols + col +
+    scr->rs_visibleoffset;
+
+ ri->ri_putchar(ri, row, col, scr->rs_bs[off].uc,
+    scr->rs_bs[off].attr);
+ }
+ }
+
+ if (scr->rs_crow != -1 && scr->rs_visibleoffset == scr->rs_dispoffset)
+ rasops_cursor(ri, 1, scr->rs_crow, scr->rs_ccol);
 }
Index: dev/rasops/rasops.h
===================================================================
RCS file: /cvs/src/sys/dev/rasops/rasops.h,v
retrieving revision 1.19
diff -u -p -u -p -r1.19 rasops.h
--- dev/rasops/rasops.h 17 Aug 2017 20:21:53 -0000 1.19
+++ dev/rasops/rasops.h 16 Apr 2018 15:40:22 -0000
@@ -178,6 +178,7 @@ int rasops_show_screen(void *, void *, i
 int rasops_load_font(void *, void *, struct wsdisplay_font *);
 int rasops_list_font(void *, struct wsdisplay_font *);
 int rasops_getchar(void *, int, int, struct wsdisplay_charcell *);
+void rasops_scrollback(void *, void *, int);
 
 extern const u_char rasops_isgray[16];
 extern const u_char rasops_cmap[256*3];
Index: dev/pci/drm/i915/i915_drv.c
===================================================================
RCS file: /cvs/src/sys/dev/pci/drm/i915/i915_drv.c,v
retrieving revision 1.109
diff -u -p -u -p -r1.109 i915_drv.c
--- dev/pci/drm/i915/i915_drv.c 22 Jan 2018 02:28:09 -0000 1.109
+++ dev/pci/drm/i915/i915_drv.c 16 Apr 2018 15:40:23 -0000
@@ -1925,6 +1925,7 @@ int inteldrm_list_font(void *, struct ws
 int inteldrm_getchar(void *, int, int, struct wsdisplay_charcell *);
 void inteldrm_burner(void *, u_int, u_int);
 void inteldrm_burner_cb(void *);
+void inteldrm_scrollback(void *, void *, int lines);
 
 struct wsscreen_descr inteldrm_stdscreen = {
  "std",
@@ -1953,6 +1954,7 @@ struct wsdisplay_accessops inteldrm_acce
  .getchar = inteldrm_getchar,
  .load_font = inteldrm_load_font,
  .list_font = inteldrm_list_font,
+ .scrollback = inteldrm_scrollback,
  .burn_screen = inteldrm_burner
 };
 
@@ -2173,6 +2175,15 @@ const struct backlight_ops inteldrm_back
  .update_status = inteldrm_backlight_update_status,
  .get_brightness = inteldrm_backlight_get_brightness
 };
+
+void
+inteldrm_scrollback(void *v, void *cookie, int lines)
+{
+ struct inteldrm_softc *dev_priv = v;
+ struct rasops_info *ri = &dev_priv->ro;
+
+ rasops_scrollback(ri, cookie, lines);
+}
 
 int inteldrm_match(struct device *, void *, void *);
 void inteldrm_attach(struct device *, struct device *, void *);

[Mark Kettenis]

> Date: Mon, 16 Apr 2018 10:45:52 -0500
> From: joshua stein <[hidden email]>

Does this do the right thing for early consoles?  The initial
efifb_bs[] doesn't have space for the scrollback.  At the point where
the scrollback code gets code, we've replaced that with a malloc'ed
buffer?

> Index: arch/amd64/amd64/efifb.c
> ===================================================================
> RCS file: /cvs/src/sys/arch/amd64/amd64/efifb.c,v
> retrieving revision 1.12
> diff -u -p -u -p -r1.12 efifb.c
> --- arch/amd64/amd64/efifb.c 28 Oct 2017 01:48:03 -0000 1.12
> +++ arch/amd64/amd64/efifb.c 16 Apr 2018 15:40:22 -0000
> @@ -101,6 +101,7 @@ int efifb_show_screen(void *, void *, i
>      void *);
>  int efifb_list_font(void *, struct wsdisplay_font *);
>  int efifb_load_font(void *, void *, struct wsdisplay_font *);
> +void efifb_scrollback(void *, void *, int lines);
>  void efifb_efiinfo_init(struct efifb *);
>  void efifb_cnattach_common(void);
>  
> @@ -133,7 +134,8 @@ struct wsdisplay_accessops efifb_accesso
>   .free_screen = efifb_free_screen,
>   .show_screen = efifb_show_screen,
>   .load_font = efifb_load_font,
> - .list_font = efifb_list_font
> + .list_font = efifb_list_font,
> + .scrollback = efifb_scrollback,
>  };
>  
>  struct cfdriver efifb_cd = {
> @@ -397,6 +399,15 @@ efifb_list_font(void *v, struct wsdispla
>   struct rasops_info *ri = &sc->sc_fb->rinfo;
>  
>   return (rasops_list_font(ri, font));
> +}
> +
> +void
> +efifb_scrollback(void *v, void *cookie, int lines)
> +{
> + struct efifb_softc *sc = v;
> + struct rasops_info *ri = &sc->sc_fb->rinfo;
> +
> + rasops_scrollback(ri, cookie, lines);
>  }
>  
>  int
> Index: dev/rasops/rasops.c
> ===================================================================
> RCS file: /cvs/src/sys/dev/rasops/rasops.c,v
> retrieving revision 1.50
> diff -u -p -u -p -r1.50 rasops.c
> --- dev/rasops/rasops.c 23 Jan 2018 10:10:32 -0000 1.50
> +++ dev/rasops/rasops.c 16 Apr 2018 15:40:22 -0000
> @@ -1373,8 +1373,13 @@ struct rasops_screen {
>   int rs_visible;
>   int rs_crow;
>   int rs_ccol;
> +
> + int rs_dispoffset; /* rs_bs index, start of our actual screen */
> + int rs_visibleoffset; /* rs_bs index, current scrollback screen */
>  };
>  
> +#define RS_SCROLLBACK_SCREENS 5
> +
>  int
>  rasops_alloc_screen(void *v, void **cookiep,
>      int *curxp, int *curyp, long *attrp)
> @@ -1387,13 +1392,15 @@ rasops_alloc_screen(void *v, void **cook
>   if (scr == NULL)
>   return (ENOMEM);
>  
> - scr->rs_bs = mallocarray(ri->ri_rows,
> + scr->rs_bs = mallocarray(ri->ri_rows * RS_SCROLLBACK_SCREENS,
>      ri->ri_cols * sizeof(struct wsdisplay_charcell), M_DEVBUF,
>      M_NOWAIT);
>   if (scr->rs_bs == NULL) {
>   free(scr, M_DEVBUF, sizeof(*scr));
>   return (ENOMEM);
>   }
> + scr->rs_visibleoffset = scr->rs_dispoffset = ri->ri_rows *
> +    (RS_SCROLLBACK_SCREENS - 1) * ri->ri_cols;
>  
>   *cookiep = scr;
>   *curxp = 0;
> @@ -1405,13 +1412,19 @@ rasops_alloc_screen(void *v, void **cook
>   scr->rs_crow = -1;
>   scr->rs_ccol = -1;
>  
> + for (i = 0; i < scr->rs_dispoffset; i++) {
> + scr->rs_bs[i].uc = ' ';
> + scr->rs_bs[i].attr = *attrp;
> + }
> +
>   if (ri->ri_bs && scr->rs_visible) {
> - memcpy(scr->rs_bs, ri->ri_bs, ri->ri_rows * ri->ri_cols *
> + memcpy(scr->rs_bs + scr->rs_dispoffset, ri->ri_bs,
> +    ri->ri_rows * ri->ri_cols *
>      sizeof(struct wsdisplay_charcell));
>   } else {
>   for (i = 0; i < ri->ri_rows * ri->ri_cols; i++) {
> - scr->rs_bs[i].uc = ' ';
> - scr->rs_bs[i].attr = *attrp;
> + scr->rs_bs[scr->rs_dispoffset + i].uc = ' ';
> + scr->rs_bs[scr->rs_dispoffset + i].attr = *attrp;
>   }
>   }
>  
> @@ -1431,7 +1444,8 @@ rasops_free_screen(void *v, void *cookie
>   ri->ri_nscreens--;
>  
>   free(scr->rs_bs, M_DEVBUF,
> -    ri->ri_rows * ri->ri_cols * sizeof(struct wsdisplay_charcell));
> +    ri->ri_rows * RS_SCROLLBACK_SCREENS * ri->ri_cols *
> +    sizeof(struct wsdisplay_charcell));
>   free(scr, M_DEVBUF, sizeof(*scr));
>  }
>  
> @@ -1467,9 +1481,11 @@ rasops_doswitch(void *v)
>   ri->ri_eraserows(ri, 0, ri->ri_rows, attr);
>   ri->ri_active = scr;
>   ri->ri_active->rs_visible = 1;
> + ri->ri_active->rs_visibleoffset = ri->ri_active->rs_dispoffset;
>   for (row = 0; row < ri->ri_rows; row++) {
>   for (col = 0; col < ri->ri_cols; col++) {
> - int off = row * scr->rs_ri->ri_cols + col;
> + int off = row * scr->rs_ri->ri_cols + col +
> +    scr->rs_visibleoffset;
>  
>   ri->ri_putchar(ri, row, col, scr->rs_bs[off].uc,
>      scr->rs_bs[off].attr);
> @@ -1491,7 +1507,7 @@ rasops_getchar(void *v, int row, int col
>   if (scr == NULL || scr->rs_bs == NULL)
>   return (1);
>  
> - *cell = scr->rs_bs[row * ri->ri_cols + col];
> + *cell = scr->rs_bs[row * ri->ri_cols + col + scr->rs_dispoffset];
>   return (0);
>  }
>  
> @@ -1521,7 +1537,10 @@ int
>  rasops_vcons_putchar(void *cookie, int row, int col, u_int uc, long attr)
>  {
>   struct rasops_screen *scr = cookie;
> - int off = row * scr->rs_ri->ri_cols + col;
> + int off = row * scr->rs_ri->ri_cols + col + scr->rs_dispoffset;
> +
> + if (scr->rs_visible && scr->rs_visibleoffset != scr->rs_dispoffset)
> + rasops_scrollback(scr->rs_ri, scr, 0);
>  
>   scr->rs_bs[off].uc = uc;
>   scr->rs_bs[off].attr = attr;
> @@ -1540,7 +1559,8 @@ rasops_vcons_copycols(void *cookie, int
>   int cols = scr->rs_ri->ri_cols;
>   int col, rc;
>  
> - memmove(&scr->rs_bs[row * cols + dst], &scr->rs_bs[row * cols + src],
> + memmove(&scr->rs_bs[row * cols + dst + scr->rs_dispoffset],
> +    &scr->rs_bs[row * cols + src + scr->rs_dispoffset],
>      num * sizeof(struct wsdisplay_charcell));
>  
>   if (!scr->rs_visible)
> @@ -1550,7 +1570,7 @@ rasops_vcons_copycols(void *cookie, int
>   return ri->ri_copycols(ri, row, src, dst, num);
>  
>   for (col = dst; col < dst + num; col++) {
> - int off = row * cols + col;
> + int off = row * cols + col + scr->rs_dispoffset;
>  
>   rc = ri->ri_putchar(ri, row, col,
>      scr->rs_bs[off].uc, scr->rs_bs[off].attr);
> @@ -1569,7 +1589,7 @@ rasops_vcons_erasecols(void *cookie, int
>   int i;
>  
>   for (i = 0; i < num; i++) {
> - int off = row * cols + col + i;
> + int off = row * cols + col + i + scr->rs_dispoffset;
>  
>   scr->rs_bs[off].uc = ' ';
>   scr->rs_bs[off].attr = attr;
> @@ -1589,8 +1609,15 @@ rasops_vcons_copyrows(void *cookie, int
>   int cols = ri->ri_cols;
>   int row, col, rc;
>  
> - memmove(&scr->rs_bs[dst * cols], &scr->rs_bs[src * cols],
> -    num * cols * sizeof(struct wsdisplay_charcell));
> + if (dst == 0 && (src + num == ri->ri_rows))
> + memmove(&scr->rs_bs[dst],
> +    &scr->rs_bs[src * cols],
> +    ((ri->ri_rows * RS_SCROLLBACK_SCREENS * cols) -
> +    (src * cols)) * sizeof(struct wsdisplay_charcell));
> + else
> + memmove(&scr->rs_bs[dst * cols + scr->rs_dispoffset],
> +    &scr->rs_bs[src * cols + scr->rs_dispoffset],
> +    num * cols * sizeof(struct wsdisplay_charcell));
>  
>   if (!scr->rs_visible)
>   return 0;
> @@ -1600,7 +1627,7 @@ rasops_vcons_copyrows(void *cookie, int
>  
>   for (row = dst; row < dst + num; row++) {
>   for (col = 0; col < cols; col++) {
> - int off = row * cols + col;
> + int off = row * cols + col + scr->rs_dispoffset;
>  
>   rc = ri->ri_putchar(ri, row, col,
>      scr->rs_bs[off].uc, scr->rs_bs[off].attr);
> @@ -1620,7 +1647,7 @@ rasops_vcons_eraserows(void *cookie, int
>   int i;
>  
>   for (i = 0; i < num * cols; i++) {
> - int off = row * cols + i;
> + int off = row * cols + i + scr->rs_dispoffset;
>  
>   scr->rs_bs[off].uc = ' ';
>   scr->rs_bs[off].attr = attr;
> @@ -1871,4 +1898,46 @@ rasops_list_font(void *v, struct wsdispl
>   font->index = idx;
>   font->cookie = font->data = NULL; /* don't leak kernel pointers */
>   return 0;
> +}
> +
> +void
> +rasops_scrollback(void *v, void *cookie, int lines)
> +{
> + struct rasops_info *ri = v;
> + struct rasops_screen *scr = cookie;
> + int row, col, oldvoff;
> + long attr;
> +
> + oldvoff = scr->rs_visibleoffset;
> +
> + if (lines == 0)
> + scr->rs_visibleoffset = scr->rs_dispoffset;
> + else {
> + int off = scr->rs_visibleoffset + (lines * ri->ri_cols);
> +
> + if (off < 0)
> + off = 0;
> + else if (off > scr->rs_dispoffset)
> + off = scr->rs_dispoffset;
> +
> + scr->rs_visibleoffset = off;
> + }
> +
> + if (scr->rs_visibleoffset == oldvoff)
> + return;
> +
> + rasops_cursor(ri, 0, 0, 0);
> + ri->ri_eraserows(ri, 0, ri->ri_rows, attr);
> + for (row = 0; row < ri->ri_rows; row++) {
> + for (col = 0; col < ri->ri_cols; col++) {
> + int off = row * scr->rs_ri->ri_cols + col +
> +    scr->rs_visibleoffset;
> +
> + ri->ri_putchar(ri, row, col, scr->rs_bs[off].uc,
> +    scr->rs_bs[off].attr);
> + }
> + }
> +
> + if (scr->rs_crow != -1 && scr->rs_visibleoffset == scr->rs_dispoffset)
> + rasops_cursor(ri, 1, scr->rs_crow, scr->rs_ccol);
>  }
> Index: dev/rasops/rasops.h
> ===================================================================
> RCS file: /cvs/src/sys/dev/rasops/rasops.h,v
> retrieving revision 1.19
> diff -u -p -u -p -r1.19 rasops.h
> --- dev/rasops/rasops.h 17 Aug 2017 20:21:53 -0000 1.19
> +++ dev/rasops/rasops.h 16 Apr 2018 15:40:22 -0000
> @@ -178,6 +178,7 @@ int rasops_show_screen(void *, void *, i
>  int rasops_load_font(void *, void *, struct wsdisplay_font *);
>  int rasops_list_font(void *, struct wsdisplay_font *);
>  int rasops_getchar(void *, int, int, struct wsdisplay_charcell *);
> +void rasops_scrollback(void *, void *, int);
>  
>  extern const u_char rasops_isgray[16];
>  extern const u_char rasops_cmap[256*3];
> Index: dev/pci/drm/i915/i915_drv.c
> ===================================================================
> RCS file: /cvs/src/sys/dev/pci/drm/i915/i915_drv.c,v
> retrieving revision 1.109
> diff -u -p -u -p -r1.109 i915_drv.c
> --- dev/pci/drm/i915/i915_drv.c 22 Jan 2018 02:28:09 -0000 1.109
> +++ dev/pci/drm/i915/i915_drv.c 16 Apr 2018 15:40:23 -0000
> @@ -1925,6 +1925,7 @@ int inteldrm_list_font(void *, struct ws
>  int inteldrm_getchar(void *, int, int, struct wsdisplay_charcell *);
>  void inteldrm_burner(void *, u_int, u_int);
>  void inteldrm_burner_cb(void *);
> +void inteldrm_scrollback(void *, void *, int lines);
>  
>  struct wsscreen_descr inteldrm_stdscreen = {
>   "std",
> @@ -1953,6 +1954,7 @@ struct wsdisplay_accessops inteldrm_acce
>   .getchar = inteldrm_getchar,
>   .load_font = inteldrm_load_font,
>   .list_font = inteldrm_list_font,
> + .scrollback = inteldrm_scrollback,
>   .burn_screen = inteldrm_burner
>  };
>  
> @@ -2173,6 +2175,15 @@ const struct backlight_ops inteldrm_back
>   .update_status = inteldrm_backlight_update_status,
>   .get_brightness = inteldrm_backlight_get_brightness
>  };
> +
> +void
> +inteldrm_scrollback(void *v, void *cookie, int lines)
> +{
> + struct inteldrm_softc *dev_priv = v;
> + struct rasops_info *ri = &dev_priv->ro;
> +
> + rasops_scrollback(ri, cookie, lines);
> +}
>  
>  int inteldrm_match(struct device *, void *, void *);
>  void inteldrm_attach(struct device *, struct device *, void *);
>
>