Re: [PATCH 2/2] vt: Distinguish between blanking and VESA blank mode in con_blank

The con_blank callback in struct consw encodes blanking and display
blank mode in a single parameter named blank. Its semantics equal
the FB_BLANK constants from the fbdev subsystems. Yet it is of type
enum vesa_blank_mode, which describes VESA DPMS levels of the attached
monitor. Although related, this is something else.

For this reason, calls to con_blank fill the blank parameter with
values that appear non-sensical at first. For example, to blank the
console, but keep the monitor on, vt passes VESA_VSYNC_SUSPEND (eq '1').
This is because consoles interpret '1' as pixels-off-but-monitor-on.
The constant VESA_VSYNC_SUSPEND actually means monitor-vsync-off. And
the argument used for monitor-vsync-off is VESA_VSYNC_SUSPEND+1.

To fix this by splitting blank into two parameters, blank and blank_mode.
The new blank is a boolean to control the display blanking. If cleared,
the console creates display output, if set the console does not. The
new parameter blank_mode specifies the VESA blank mode for the monitor
and equals VESA DPMS levels. If blank is set, blank_mode gives a hint
to the console, on how to set up the signal to the monitor.

The actual interpretation is up to the console. Newportcon and sticon
only handle blank or not-blank. Fbcon and vgacon implement blank plus
the VESA DPMS handling. The implementation of both consoles is again
somewhat confusing because types and values do not match. Clean up
both with the new blank/blank_mode logic.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
---
 drivers/tty/vt/vt.c                 | 11 ++++----
 drivers/video/console/dummycon.c    |  4 +--
 drivers/video/console/newport_con.c |  4 +--
 drivers/video/console/sticon.c      |  4 +--
 drivers/video/console/vgacon.c      | 44 +++++++++++++++--------------
 drivers/video/fbdev/core/fbcon.c    | 19 +++++++------
 include/linux/console.h             |  9 ++++--
 7 files changed, 51 insertions(+), 44 deletions(-)

diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c
index 9e7b4419b422..f762c965351d 100644
--- a/drivers/tty/vt/vt.c
+++ b/drivers/tty/vt/vt.c

@@ -4671,7 +4671,7 @@ void do_blank_screen(bool entering_gfx)
 	if (console_blanked) {
 		if (blank_state == blank_vesa_wait) {
 			blank_state = blank_off;
-			vc->vc_sw->con_blank(vc, vesa_blank_mode + 1, false);
+			vc->vc_sw->con_blank(vc, true, vesa_blank_mode, false);

-static bool vgacon_blank(struct vc_data *c, enum vesa_blank_mode blank,
+static bool vgacon_blank(struct vc_data *c, bool blank, enum vesa_blank_mode blank_mode,
 			 bool mode_switch)
 {
-	switch (blank) {
-	case VESA_NO_BLANKING:		/* Unblank */
+	if (blank) {
+		switch (blank_mode) {
+		case VESA_NO_BLANKING:	/* Normal blanking */
+			if (!mode_switch && vga_video_type == VIDEO_TYPE_VGAC) {
+				vga_pal_blank(&vgastate);
+				vga_palette_blanked = true;
+				return 0;
+			}
+			vgacon_set_origin(c);
+			scr_memsetw((void *)vga_vram_base, BLANK,
+				    c->vc_screenbuf_size);
+			if (mode_switch)
+				vga_is_gfx = true;
+			return 1;
+		default:		/* VESA blanking */
+			if (vga_video_type == VIDEO_TYPE_VGAC) {
+				vga_vesa_blank(&vgastate, blank_mode);
+				vga_vesa_blanked = blank_mode;
+			}
+			return 0;
+		}
+	} else { /* Unblank */
 		if (vga_vesa_blanked) {
 			vga_vesa_unblank(&vgastate);
 			vga_vesa_blanked = VESA_NO_BLANKING;

@@ -814,24 +834,6 @@ static bool vgacon_blank(struct vc_data *c, enum vesa_blank_mode blank,
 		vga_is_gfx = false;
 		/* Tell console.c that it has to restore the screen itself */
 		return 1;
-	case VESA_VSYNC_SUSPEND:	/* Normal blanking */
-		if (!mode_switch && vga_video_type == VIDEO_TYPE_VGAC) {
-			vga_pal_blank(&vgastate);
-			vga_palette_blanked = true;
-			return 0;
-		}
-		vgacon_set_origin(c);
-		scr_memsetw((void *) vga_vram_base, BLANK,
-			    c->vc_screenbuf_size);
-		if (mode_switch)
-			vga_is_gfx = true;
-		return 1;
-	default:		/* VESA blanking */
-		if (vga_video_type == VIDEO_TYPE_VGAC) {
-			vga_vesa_blank(&vgastate, blank - 1);
-			vga_vesa_blanked = blank;
-		}
-		return 0;
 	}