[PATCH] vga text console and stty cols/rows

Some people use 66-cells braille devices for reading the console, and hence
would like to reduce the width of the screen by using:

stty cols 66

However, the vga text console doesn't behave correctly: the 14 first
characters of the second line are put on the right of the first line and so
forth.

Here is a patch to correct that.  It corrects the disp_end and offset
registers of the vga board on console resize and console switch.

On usual screens, you then correctly get a right and/or bottom blank
margin.  On some laptop panels, the output is resized so that text actually
gets magnified, which can be great for some people (see
http://dept-info.labri.fr/~thibault/ls.jpg ).

Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 69 insertions, 2 deletions

diff --git a/drivers/video/console/vgacon.c b/drivers/video/console/vgacon.c
index d27fa91e5886..0705cd741411 100644
--- a/drivers/video/console/vgacon.c
+++ b/drivers/video/console/vgacon.c
@@ -497,6 +497,57 @@ static void vgacon_cursor(struct vc_data *c, int mode)
         }
 }
 
+static int vgacon_doresize(struct vc_data *c,
+                unsigned int width, unsigned int height)
+{
+        unsigned long flags;
+        unsigned int scanlines = height * c->vc_font.height;
+        u8 scanlines_lo, r7, vsync_end, mode;
+
+        spin_lock_irqsave(&vga_lock, flags);
+
+        outb_p(VGA_CRTC_MODE, vga_video_port_reg);
+        mode = inb_p(vga_video_port_val);
+
+        if (mode & 0x04)
+                scanlines >>= 1;
+
+        scanlines -= 1;
+        scanlines_lo = scanlines & 0xff;
+
+        outb_p(VGA_CRTC_OVERFLOW, vga_video_port_reg);
+        r7 = inb_p(vga_video_port_val) & ~0x42;
+
+        if (scanlines & 0x100)
+                r7 |= 0x02;
+        if (scanlines & 0x200)
+                r7 |= 0x40;
+
+        /* deprotect registers */
+        outb_p(VGA_CRTC_V_SYNC_END, vga_video_port_reg);
+        vsync_end = inb_p(vga_video_port_val);
+        outb_p(VGA_CRTC_V_SYNC_END, vga_video_port_reg);
+        outb_p(vsync_end & ~0x80, vga_video_port_val);
+
+        outb_p(VGA_CRTC_H_DISP, vga_video_port_reg);
+        outb_p(width - 1, vga_video_port_val);
+        outb_p(VGA_CRTC_OFFSET, vga_video_port_reg);
+        outb_p(width >> 1, vga_video_port_val);
+
+        outb_p(VGA_CRTC_V_DISP_END, vga_video_port_reg);
+        outb_p(scanlines_lo, vga_video_port_val);
+        outb_p(VGA_CRTC_OVERFLOW, vga_video_port_reg);
+        outb_p(r7,vga_video_port_val);
+
+        /* reprotect registers */
+        outb_p(VGA_CRTC_V_SYNC_END, vga_video_port_reg);
+        outb_p(vsync_end, vga_video_port_val);
+
+        spin_unlock_irqrestore(&vga_lock, flags);
+
+        return 0;
+}
+
 static int vgacon_switch(struct vc_data *c)
 {
         /*
@@ -510,9 +561,13 @@ static int vgacon_switch(struct vc_data *c)
         /* We can only copy out the size of the video buffer here,
          * otherwise we get into VGA BIOS */
 
-        if (!vga_is_gfx)
+        if (!vga_is_gfx) {
                 scr_memcpyw((u16 *) c->vc_origin, (u16 *) c->vc_screenbuf,
-                            c->vc_screenbuf_size > vga_vram_size ? vga_vram_size : c->vc_screenbuf_size);
+                            c->vc_screenbuf_size > vga_vram_size ?
+                                vga_vram_size : c->vc_screenbuf_size);
+                vgacon_doresize(c, c->vc_cols, c->vc_rows);
+        }
+
         return 0;               /* Redrawing not needed */
 }
 
@@ -962,6 +1017,17 @@ static int vgacon_font_get(struct vc_data *c, struct console_font *font)
 
 #endif
 
+static int vgacon_resize(struct vc_data *c, unsigned int width,
+                                unsigned int height)
+{
+        if (width % 2 || width > ORIG_VIDEO_COLS || height > ORIG_VIDEO_LINES)
+                return -EINVAL;
+
+        if (CON_IS_VISIBLE(c) && !vga_is_gfx) /* who knows */
+                vgacon_doresize(c, width, height);
+        return 0;
+}
+
 static int vgacon_scrolldelta(struct vc_data *c, int lines)
 {
         if (!lines)             /* Turn scrollback off */
@@ -1103,6 +1169,7 @@ const struct consw vga_con = {
         .con_blank = vgacon_blank,
         .con_font_set = vgacon_font_set,
         .con_font_get = vgacon_font_get,
+        .con_resize = vgacon_resize,
         .con_set_palette = vgacon_set_palette,
         .con_scrolldelta = vgacon_scrolldelta,
         .con_set_origin = vgacon_set_origin,