Re: [PATCH] Use correct erase colour for clearing in fbcon

Helge Deller <deller@xxxxxx> · Mon, 3 Feb 2025 20:42:41 +0100

On 2/2/25 21:33, Kajtár Zsolt wrote:
The erase colour calculation for fbcon clearing should use get_color instead
of attr_col_ec, like everything else. The latter is similar but is not correct.
For example it's missing the depth dependent remapping and doesn't care about
blanking.

The problem can be reproduced by setting up the background colour to grey
(vt.color=0x70) and having an fbcon console set to 2bpp (4 shades of gray).
Now the background attribute should be 1 (dark gray) on the console.

If the screen is scrolled when pressing enter in a shell prompt at the bottom
line then the new line is cleared using colour 7 instead of 1. That's not
something fillrect likes (at 2bbp it expect 0-3) so the result is interesting.

This patch switches to get_color with vc_video_erase_char to determine the
erase colour from attr_col_ec. That makes the latter function redundant as
no other users were left.

Use correct erase colour for clearing in fbcon

Signed-off-by: Zsolt Kajtar <soci@xxxxxxxxxxxxx>


applied for further testing to fbdev git tree.

Helge

---
  drivers/video/fbdev/core/bitblit.c   |  5 ++--
  drivers/video/fbdev/core/fbcon.c     | 10 +++++---
  drivers/video/fbdev/core/fbcon.h     | 38 +---------------------------
  drivers/video/fbdev/core/fbcon_ccw.c |  5 ++--
  drivers/video/fbdev/core/fbcon_cw.c  |  5 ++--
  drivers/video/fbdev/core/fbcon_ud.c  |  5 ++--
  drivers/video/fbdev/core/tileblit.c  |  8 +++---
  7 files changed, 18 insertions(+), 58 deletions(-)

diff --git a/drivers/video/fbdev/core/bitblit.c b/drivers/video/fbdev/core/bitblit.c
index 3ff1b2a86..f9475c14f 100644
--- a/drivers/video/fbdev/core/bitblit.c
+++ b/drivers/video/fbdev/core/bitblit.c
@@ -59,12 +59,11 @@ static void bit_bmove(struct vc_data *vc, struct fb_info *info, int sy,
  }

  static void bit_clear(struct vc_data *vc, struct fb_info *info, int sy,
-		      int sx, int height, int width)
+		      int sx, int height, int width, int fg, int bg)
  {
-	int bgshift = (vc->vc_hi_font_mask) ? 13 : 12;
  	struct fb_fillrect region;

-	region.color = attr_bgcol_ec(bgshift, vc, info);
+	region.color = bg;
  	region.dx = sx * vc->vc_font.width;
  	region.dy = sy * vc->vc_font.height;
  	region.width = width * vc->vc_font.width;
diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c
index e8b4e8c11..07d127110 100644
--- a/drivers/video/fbdev/core/fbcon.c
+++ b/drivers/video/fbdev/core/fbcon.c
@@ -1258,7 +1258,7 @@ static void __fbcon_clear(struct vc_data *vc, unsigned int sy, unsigned int sx,
  {
  	struct fb_info *info = fbcon_info_from_console(vc->vc_num);
  	struct fbcon_ops *ops = info->fbcon_par;
-
+	int fg, bg;
  	struct fbcon_display *p = &fb_display[vc->vc_num];
  	u_int y_break;

@@ -1279,16 +1279,18 @@ static void __fbcon_clear(struct vc_data *vc, unsigned int sy, unsigned int sx,
  		fbcon_clear_margins(vc, 0);
  	}

+	fg = get_color(vc, info, vc->vc_video_erase_char, 1);
+	bg = get_color(vc, info, vc->vc_video_erase_char, 0);
  	/* Split blits that cross physical y_wrap boundary */

  	y_break = p->vrows - p->yscroll;
  	if (sy < y_break && sy + height - 1 >= y_break) {
  		u_int b = y_break - sy;
-		ops->clear(vc, info, real_y(p, sy), sx, b, width);
+		ops->clear(vc, info, real_y(p, sy), sx, b, width, fg, bg);
  		ops->clear(vc, info, real_y(p, sy + b), sx, height - b,
-				 width);
+				 width, fg, bg);
  	} else
-		ops->clear(vc, info, real_y(p, sy), sx, height, width);
+		ops->clear(vc, info, real_y(p, sy), sx, height, width, fg, bg);
  }

  static void fbcon_clear(struct vc_data *vc, unsigned int sy, unsigned int sx,
diff --git a/drivers/video/fbdev/core/fbcon.h b/drivers/video/fbdev/core/fbcon.h
index df70ea5ec..4d97e6d8a 100644
--- a/drivers/video/fbdev/core/fbcon.h
+++ b/drivers/video/fbdev/core/fbcon.h
@@ -55,7 +55,7 @@ struct fbcon_ops {
  	void (*bmove)(struct vc_data *vc, struct fb_info *info, int sy,
  		      int sx, int dy, int dx, int height, int width);
  	void (*clear)(struct vc_data *vc, struct fb_info *info, int sy,
-		      int sx, int height, int width);
+		      int sx, int height, int width, int fb, int bg);
  	void (*putcs)(struct vc_data *vc, struct fb_info *info,
  		      const unsigned short *s, int count, int yy, int xx,
  		      int fg, int bg);
@@ -116,42 +116,6 @@ static inline int mono_col(const struct fb_info *info)
  	return (~(0xfff << max_len)) & 0xff;
  }

-static inline int attr_col_ec(int shift, struct vc_data *vc,
-			      struct fb_info *info, int is_fg)
-{
-	int is_mono01;
-	int col;
-	int fg;
-	int bg;
-
-	if (!vc)
-		return 0;
-
-	if (vc->vc_can_do_color)
-		return is_fg ? attr_fgcol(shift,vc->vc_video_erase_char)
-			: attr_bgcol(shift,vc->vc_video_erase_char);
-
-	if (!info)
-		return 0;
-
-	col = mono_col(info);
-	is_mono01 = info->fix.visual == FB_VISUAL_MONO01;
-
-	if (attr_reverse(vc->vc_video_erase_char)) {
-		fg = is_mono01 ? col : 0;
-		bg = is_mono01 ? 0 : col;
-	}
-	else {
-		fg = is_mono01 ? 0 : col;
-		bg = is_mono01 ? col : 0;
-	}
-
-	return is_fg ? fg : bg;
-}
-
-#define attr_bgcol_ec(bgshift, vc, info) attr_col_ec(bgshift, vc, info, 0)
-#define attr_fgcol_ec(fgshift, vc, info) attr_col_ec(fgshift, vc, info, 1)
-
      /*
       *  Scroll Method
       */
diff --git a/drivers/video/fbdev/core/fbcon_ccw.c b/drivers/video/fbdev/core/fbcon_ccw.c
index f9b794ff7..89ef4ba7e 100644
--- a/drivers/video/fbdev/core/fbcon_ccw.c
+++ b/drivers/video/fbdev/core/fbcon_ccw.c
@@ -78,14 +78,13 @@ static void ccw_bmove(struct vc_data *vc, struct fb_info *info, int sy,
  }

  static void ccw_clear(struct vc_data *vc, struct fb_info *info, int sy,
-		     int sx, int height, int width)
+		     int sx, int height, int width, int fg, int bg)
  {
  	struct fbcon_ops *ops = info->fbcon_par;
  	struct fb_fillrect region;
-	int bgshift = (vc->vc_hi_font_mask) ? 13 : 12;
  	u32 vyres = GETVYRES(ops->p, info);

-	region.color = attr_bgcol_ec(bgshift,vc,info);
+	region.color = bg;
  	region.dx = sy * vc->vc_font.height;
  	region.dy = vyres - ((sx + width) * vc->vc_font.width);
  	region.height = width * vc->vc_font.width;
diff --git a/drivers/video/fbdev/core/fbcon_cw.c b/drivers/video/fbdev/core/fbcon_cw.c
index 903f6fc17..b9dac7940 100644
--- a/drivers/video/fbdev/core/fbcon_cw.c
+++ b/drivers/video/fbdev/core/fbcon_cw.c
@@ -63,14 +63,13 @@ static void cw_bmove(struct vc_data *vc, struct fb_info *info, int sy,
  }

  static void cw_clear(struct vc_data *vc, struct fb_info *info, int sy,
-		     int sx, int height, int width)
+		     int sx, int height, int width, int fg, int bg)
  {
  	struct fbcon_ops *ops = info->fbcon_par;
  	struct fb_fillrect region;
-	int bgshift = (vc->vc_hi_font_mask) ? 13 : 12;
  	u32 vxres = GETVXRES(ops->p, info);

-	region.color = attr_bgcol_ec(bgshift,vc,info);
+	region.color = bg;
  	region.dx = vxres - ((sy + height) * vc->vc_font.height);
  	region.dy = sx *  vc->vc_font.width;
  	region.height = width * vc->vc_font.width;
diff --git a/drivers/video/fbdev/core/fbcon_ud.c b/drivers/video/fbdev/core/fbcon_ud.c
index 594331936..0af7913a2 100644
--- a/drivers/video/fbdev/core/fbcon_ud.c
+++ b/drivers/video/fbdev/core/fbcon_ud.c
@@ -64,15 +64,14 @@ static void ud_bmove(struct vc_data *vc, struct fb_info *info, int sy,
  }

  static void ud_clear(struct vc_data *vc, struct fb_info *info, int sy,
-		     int sx, int height, int width)
+		     int sx, int height, int width, int fg, int bg)
  {
  	struct fbcon_ops *ops = info->fbcon_par;
  	struct fb_fillrect region;
-	int bgshift = (vc->vc_hi_font_mask) ? 13 : 12;
  	u32 vyres = GETVYRES(ops->p, info);
  	u32 vxres = GETVXRES(ops->p, info);

-	region.color = attr_bgcol_ec(bgshift,vc,info);
+	region.color = bg;
  	region.dy = vyres - ((sy + height) * vc->vc_font.height);
  	region.dx = vxres - ((sx + width) *  vc->vc_font.width);
  	region.width = width * vc->vc_font.width;
diff --git a/drivers/video/fbdev/core/tileblit.c b/drivers/video/fbdev/core/tileblit.c
index eff7ec4da..45b0828fa 100644
--- a/drivers/video/fbdev/core/tileblit.c
+++ b/drivers/video/fbdev/core/tileblit.c
@@ -32,16 +32,14 @@ static void tile_bmove(struct vc_data *vc, struct fb_info *info, int sy,
  }

  static void tile_clear(struct vc_data *vc, struct fb_info *info, int sy,
-		       int sx, int height, int width)
+		       int sx, int height, int width, int fg, int bg)
  {
  	struct fb_tilerect rect;
-	int bgshift = (vc->vc_hi_font_mask) ? 13 : 12;
-	int fgshift = (vc->vc_hi_font_mask) ? 9 : 8;

  	rect.index = vc->vc_video_erase_char &
  		((vc->vc_hi_font_mask) ? 0x1ff : 0xff);
-	rect.fg = attr_fgcol_ec(fgshift, vc, info);
-	rect.bg = attr_bgcol_ec(bgshift, vc, info);
+	rect.fg = fg;
+	rect.bg = bg;
  	rect.sx = sx;
  	rect.sy = sy;
  	rect.width = width;








