[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>

diff --git a/drivers/video/console/vgacon.c b/drivers/video/console/vgacon.c
index d27fa91..0705cd7 100644 (file)
--- 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,