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rasops: implement scrollback for inteldrm and efifb

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joshua stein-3

rasops: implement scrollback for inteldrm and efifb

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

Re: rasops: implement scrollback for inteldrm and efifb

> 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 *);
>
>

joshua stein-3

Re: rasops: implement scrollback for inteldrm and efifb

On Tue, 17 Apr 2018 at 07:52:28 +0200, Mark Kettenis wrote:
> > 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?

Here is a new version that puts the scrollback count into each
rasops_screen in case it changes later, which allows it to cope with
the count being 0 if no scrollback has been allocated.

Though the scrollback callback won't be called until wsdisplay
formally attaches later after each rasops_screen is allocated
anyway.

Index: arch/amd64/amd64/efifb.c
===================================================================
RCS file: /cvs/src/sys/arch/amd64/amd64/efifb.c,v
retrieving revision 1.15
diff -u -p -u -p -r1.15 efifb.c
--- arch/amd64/amd64/efifb.c 25 Apr 2018 00:46:28 -0000 1.15
+++ arch/amd64/amd64/efifb.c 27 Apr 2018 14:27:22 -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 1.52
diff -u -p -u -p -r1.52 rasops.c
--- dev/rasops/rasops.c 20 Apr 2018 16:09:37 -0000 1.52
+++ dev/rasops/rasops.c 27 Apr 2018 14:27:23 -0000
@@ -1373,6 +1373,11 @@ struct rasops_screen {
int rs_visible;
int rs_crow;
int rs_ccol;
+
+ int rs_sbscreens;
+#define RS_SCROLLBACK_SCREENS 5
+ int rs_dispoffset; /* rs_bs index, start of our actual screen */
+ int rs_visibleoffset; /* rs_bs index, current scrollback screen */
};

int
@@ -1387,13 +1392,16 @@ rasops_alloc_screen(void *v, void **cook
if (scr == NULL)
return (ENOMEM);

- scr->rs_bs = mallocarray(ri->ri_rows,
+ scr->rs_sbscreens = RS_SCROLLBACK_SCREENS;
+ scr->rs_bs = mallocarray(ri->ri_rows * (scr->rs_sbscreens + 1),
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 *
+ scr->rs_sbscreens * ri->ri_cols;

*cookiep = scr;
*curxp = 0;
@@ -1405,13 +1413,19 @@ 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 +1445,8 @@ 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 * (scr->rs_sbscreens + 1) * ri->ri_cols *
+ sizeof(struct wsdisplay_charcell));
free(scr, M_DEVBUF, sizeof(*scr));
}

@@ -1467,9 +1482,11 @@ 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 +1508,7 @@ 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 +1538,10 @@ 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 +1560,8 @@ 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 +1571,7 @@ 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 +1590,7 @@ 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 +1610,15 @@ 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) && scr->rs_sbscreens)
+ memmove(&scr->rs_bs[dst], &scr->rs_bs[src * cols],
+ ((ri->ri_rows * (scr->rs_sbscreens + 1) * 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 +1628,7 @@ 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 +1648,7 @@ 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 +1899,46 @@ 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 1.21
diff -u -p -u -p -r1.21 rasops.h
--- dev/rasops/rasops.h 20 Apr 2018 16:09:37 -0000 1.21
+++ dev/rasops/rasops.h 27 Apr 2018 14:27:23 -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 1.111
diff -u -p -u -p -r1.111 i915_drv.c
--- dev/pci/drm/i915/i915_drv.c 20 Apr 2018 16:09:36 -0000 1.111
+++ dev/pci/drm/i915/i915_drv.c 27 Apr 2018 14:27:23 -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

Re: rasops: implement scrollback for inteldrm and efifb

> Date: Fri, 27 Apr 2018 09:33:31 -0500
> From: joshua stein <[hidden email]>
>
> On Tue, 17 Apr 2018 at 07:52:28 +0200, Mark Kettenis wrote:
> > > 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?
>
> Here is a new version that puts the scrollback count into each
> rasops_screen in case it changes later, which allows it to cope with
> the count being 0 if no scrollback has been allocated.
>
> Though the scrollback callback won't be called until wsdisplay
> formally attaches later after each rasops_screen is allocated
> anyway.

Two small nits below. Otherwise this looks fine, so ok kettenis@ if
you fix those.

Should really use scr->rs_sbscreens > 0 here.

> + memmove(&scr->rs_bs[dst], &scr->rs_bs[src * cols],
> + ((ri->ri_rows * (scr->rs_sbscreens + 1) * cols) -
> + (src * cols)) *
> + sizeof(struct wsdisplay_charcell));

That sizeof fits on the previous line.

> + 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 +1628,7 @@ 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 +1648,7 @@ 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 +1899,46 @@ 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 1.21
> diff -u -p -u -p -r1.21 rasops.h
> --- dev/rasops/rasops.h 20 Apr 2018 16:09:37 -0000 1.21
> +++ dev/rasops/rasops.h 27 Apr 2018 14:27:23 -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 1.111
> diff -u -p -u -p -r1.111 i915_drv.c
> --- dev/pci/drm/i915/i915_drv.c 20 Apr 2018 16:09:36 -0000 1.111
> +++ dev/pci/drm/i915/i915_drv.c 27 Apr 2018 14:27:23 -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 *);
>
>

Jonathan Gray-11

Re: rasops: implement scrollback for inteldrm and efifb

On Fri, Apr 27, 2018 at 10:22:42PM +0200, Mark Kettenis wrote:

> > Date: Fri, 27 Apr 2018 09:33:31 -0500
> > From: joshua stein <[hidden email]>
> >
> > On Tue, 17 Apr 2018 at 07:52:28 +0200, Mark Kettenis wrote:
> > > > 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?
> >
> > Here is a new version that puts the scrollback count into each
> > rasops_screen in case it changes later, which allows it to cope with
> > the count being 0 if no scrollback has been allocated.
> >
> > Though the scrollback callback won't be called until wsdisplay
> > formally attaches later after each rasops_screen is allocated
> > anyway.
>
> Two small nits below. Otherwise this looks fine, so ok kettenis@ if
> you fix those.

I haven't tried this on intel yet but on radeon I often see a thin red
vertical line on the right side of the display with the first screen of
the buffer when scrolling back on rv635.

Index: radeon_kms.c
===================================================================
RCS file: /cvs/src/sys/dev/pci/drm/radeon/radeon_kms.c,v
retrieving revision 1.55
diff -u -p -r1.55 radeon_kms.c
--- radeon_kms.c 25 Apr 2018 01:27:46 -0000 1.55
+++ radeon_kms.c 28 Apr 2018 01:39:19 -0000
@@ -202,6 +202,7 @@ struct wsdisplay_accessops radeondrm_acc
.getchar = rasops_getchar,
.load_font = rasops_load_font,
.list_font = rasops_list_font,
+ .scrollback = rasops_scrollback,
.burn_screen = radeondrm_burner
};