[PATCH] fbcon: Console Rotation - Prepare fbcon for console rotation

This patch series implements generic code to rotate the console at 90, 180,
and 270 degrees. The implementation is completely done in the framebuffer
console level, thus no changes to the framebuffer layer or to the drivers
are needed.

Console rotation is required by some Sharp-based devices where the natural
orientation of the display is not at 0 degrees. Also, users that have
displays that can pivot will benefit by having a console in portrait mode
if they so desire.

The choice to implement the code in the console layer rather than in the
framebuffer layer is due to the following reasons:

- it's fast
- it does not require driver changes
- it can coexist with devices that can rotate the display at the hardware level
- it complements graphics applications that can do display rotation

The changes to core fbcon are minimal-- recognition of the console
rotation angle so it can swap directions, origins and axes (xres vs yres,
xpanstep vs ypanstep, xoffset vs yoffset, etc) and storage of the rotation
angle per display. The bulk of the code that does the actual drawing to the
screen are placed in separate files. Each angle of rotation has separate
methods (bmove, clear, putcs, cursor, update_start which is derived from
update_var, and clear_margins).  To mimimize processing time, the fontdata
are pre-rotated at each console switch (only if the font or the angle has
changed).

The option can be compiled out (CONFIG_FRAMEBUFFER_CONSOLE_ROTATION = n) if
rotation is not needed.

Choosing the rotation angle can be done in several ways:

1. boot option fbcon=rotate:n, where
     n = 0 - normal
     n = 1 - 90 degrees (clockwise)
     n = 2 - 180 degrees (upside down)
     n = 3 - 270 degrees (counterclockwise)

2. echo n > /sys/class/graphics/fb[num]/con_rotate

     where n is the same as described above. It sets the angle of rotation
of the current console

3 echo n > /sys/class/graphics/fb[num]/con_rotate_all

     where n is the same as described above. Globally sets the angle of
rotation.

GOTCHAS:

	The option, especially at angles of 90 and 270 degrees, will exercise
the least used code of drivers.  Namely, at these angles, panning is done
in the x-axis, so it can reveal bugs in the driver if xpanstep is set
incorrectly. A workaround is to set xpanstep = 0.

	Secondly, at these angles, the framebuffer memory access can be
unaligned if (fontheight * bpp) % 32 ~= 0 which can reveal bugs in the drivers
imageblit, fillrect and copyarea functions.  (I think cfbfillrect may have
this buglet). A workaround is to use a standard 8x16 font.

Speed:

	The scrolling speed difference between 0 and 180 degrees is minimal,
somewhere areound 1-2%.  At 90 or 270 degress, speed drops down to a vicinity
of 30-40%. This is understandable because the blit direction is across the
framebuffer "direction." Scrolling will be helped at these angles if xpanstep
is not equal to zero, use of 8x16 fonts, and setting xres_virtual >= xres * 2.

Note: The code is tested on little-endian only, so I don't know if it will
work in big-endian. Please let me know, it will take only less than a minute
of your time.

This patch prepares fbcon for console rotation and contains the following
changes:

- add rotate field in struct fbcon_ops to keep fbcon's current rotation
  angle

- add con_rotate field in struct display to store per-display rotation angle

- create a private copy of the current var to fbcon.  This will prevent
  fbcon from directly manipulating info->var, especially the fields xoffset,
  yoffset and vmode.

- add ability to swap pertinent axes (xres, yres; xpanstep, ypanstep; etc)
  depending on the rotation angle

- change global update_var() (function that sets the screen start address)
  as an fbcon method update_start.  This is required because the axes, start
  offset, and/or direction can be reversed depending on the rotation angle.

- add fbcon method rotate_font() which will rotate each character bitmap to
  the correct angle of rotation.

- add fbcon boot option 'rotate' to select the angle of rotation at bootime.
   Currently does nothing until all patches are applied.
Signed-off-by: Antonino Daplas <adaplas@pol.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

drivers/video/console/Kconfig

@@ -101,6 +101,16 @@ config FRAMEBUFFER_CONSOLE
 	help
 	  Low-level framebuffer-based console driver.
 
+config FRAMEBUFFER_CONSOLE_ROTATION
+       bool "Framebuffer Console Rotation"
+       depends on FRAMEBUFFER_CONSOLE
+       help
+         Enable display rotation for the framebuffer console.  This is done
+         in software and may be significantly slower than a normally oriented
+         display.  Note that the rotation is done at the console level only
+         such that other users of the framebuffer will remain normally
+         oriented.
+
 config STI_CONSOLE
         tristate "STI text console" 
         depends on PARISC

drivers/video/console/bitblit.c

@@ -22,35 +22,6 @@
 /*
  * Accelerated handlers.
  */
-#define FBCON_ATTRIBUTE_UNDERLINE 1
-#define FBCON_ATTRIBUTE_REVERSE   2
-#define FBCON_ATTRIBUTE_BOLD      4
-
-static inline int real_y(struct display *p, int ypos)
-{
-	int rows = p->vrows;
-
-	ypos += p->yscroll;
-	return ypos < rows ? ypos : ypos - rows;
-}
-
-
-static inline int get_attribute(struct fb_info *info, u16 c)
-{
-	int attribute = 0;
-
-	if (fb_get_color_depth(&info->var, &info->fix) == 1) {
-		if (attr_underline(c))
-			attribute |= FBCON_ATTRIBUTE_UNDERLINE;
-		if (attr_reverse(c))
-			attribute |= FBCON_ATTRIBUTE_REVERSE;
-		if (attr_bold(c))
-			attribute |= FBCON_ATTRIBUTE_BOLD;
-	}
-
-	return attribute;
-}
-
 static inline void update_attr(u8 *dst, u8 *src, int attribute,
 			       struct vc_data *vc)
 {
@@ -418,6 +389,18 @@ static void bit_cursor(struct vc_data *vc, struct fb_info *info,
 	ops->cursor_reset = 0;
 }
 
+static int bit_update_start(struct fb_info *info)
+{
+	struct fbcon_ops *ops = info->fbcon_par;
+	int err;
+
+	err = fb_pan_display(info, &ops->var);
+	ops->var.xoffset = info->var.xoffset;
+	ops->var.yoffset = info->var.yoffset;
+	ops->var.vmode = info->var.vmode;
+	return err;
+}
+
 void fbcon_set_bitops(struct fbcon_ops *ops)
 {
 	ops->bmove = bit_bmove;
@@ -425,6 +408,11 @@ void fbcon_set_bitops(struct fbcon_ops *ops)
 	ops->putcs = bit_putcs;
 	ops->clear_margins = bit_clear_margins;
 	ops->cursor = bit_cursor;
+	ops->update_start = bit_update_start;
+	ops->rotate_font = NULL;
+
+	if (ops->rotate)
+		fbcon_set_rotate(ops);
 }
 
 EXPORT_SYMBOL(fbcon_set_bitops);

drivers/video/console/fbcon.h

@@ -27,15 +27,15 @@
     */
 
 struct display {
-    /* Filled in by the frame buffer device */
-    u_short inverse;                /* != 0 text black on white as default */
     /* Filled in by the low-level console driver */
     const u_char *fontdata;
     int userfont;                   /* != 0 if fontdata kmalloc()ed */
     u_short scrollmode;             /* Scroll Method */
+    u_short inverse;                /* != 0 text black on white as default */
     short yscroll;                  /* Hardware scrolling */
     int vrows;                      /* number of virtual rows */
     int cursor_shape;
+    int con_rotate;
     u32 xres_virtual;
     u32 yres_virtual;
     u32 height;
@@ -52,6 +52,8 @@ struct display {
     struct fb_videomode *mode;
 };
 
+extern struct display fb_display[];
+
 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);
@@ -63,8 +65,12 @@ struct fbcon_ops {
 	void (*clear_margins)(struct vc_data *vc, struct fb_info *info,
 			      int bottom_only);
 	void (*cursor)(struct vc_data *vc, struct fb_info *info,
-		       struct display *p, int mode, int softback_lines, int fg, int bg);
-
+		       struct display *p, int mode, int softback_lines,
+		       int fg, int bg);
+	int  (*update_start)(struct fb_info *info);
+	int  (*rotate_font)(struct fb_info *info, struct vc_data *vc,
+			    struct display *p);
+	struct fb_var_screeninfo var;  /* copy of the current fb_var_screeninfo */
 	struct timer_list cursor_timer; /* Cursor timer */
 	struct fb_cursor cursor_state;
         int    currcon;	                /* Current VC. */
@@ -73,7 +79,12 @@ struct fbcon_ops {
 	int    blank_state;
 	int    graphics;
 	int    flags;
+	int    rotate;
+	int    cur_rotate;
 	char  *cursor_data;
+	u8    *fontbuffer;
+	u8    *fontdata;
+	u32    fd_size;
 };
     /*
      *  Attribute Decoding
@@ -168,4 +179,43 @@ extern void fbcon_set_tileops(struct vc_data *vc, struct fb_info *info,
 #endif
 extern void fbcon_set_bitops(struct fbcon_ops *ops);
 extern int  soft_cursor(struct fb_info *info, struct fb_cursor *cursor);
+
+#define FBCON_ATTRIBUTE_UNDERLINE 1
+#define FBCON_ATTRIBUTE_REVERSE   2
+#define FBCON_ATTRIBUTE_BOLD      4
+
+static inline int real_y(struct display *p, int ypos)
+{
+	int rows = p->vrows;
+
+	ypos += p->yscroll;
+	return ypos < rows ? ypos : ypos - rows;
+}
+
+
+static inline int get_attribute(struct fb_info *info, u16 c)
+{
+	int attribute = 0;
+
+	if (fb_get_color_depth(&info->var, &info->fix) == 1) {
+		if (attr_underline(c))
+			attribute |= FBCON_ATTRIBUTE_UNDERLINE;
+		if (attr_reverse(c))
+			attribute |= FBCON_ATTRIBUTE_REVERSE;
+		if (attr_bold(c))
+			attribute |= FBCON_ATTRIBUTE_BOLD;
+	}
+
+	return attribute;
+}
+
+#define FBCON_SWAP(i,r,v) ({ \
+        typeof(r) _r = (r);  \
+        typeof(v) _v = (v);  \
+        (void) (&_r == &_v); \
+        (i == FB_ROTATE_UR || i == FB_ROTATE_UD) ? _r : _v; })
+
+#define fbcon_set_rotate(x) do {} while(0)
+
 #endif /* _VIDEO_FBCON_H */
+

drivers/video/console/tileblit.c

@@ -118,6 +118,18 @@ static void tile_cursor(struct vc_data *vc, struct fb_info *info,
 	info->tileops->fb_tilecursor(info, &cursor);
 }
 
+static int tile_update_start(struct fb_info *info)
+{
+	struct fbcon_ops *ops = info->fbcon_par;
+	int err;
+
+	err = fb_pan_display(info, &ops->var);
+	ops->var.xoffset = info->var.xoffset;
+	ops->var.yoffset = info->var.yoffset;
+	ops->var.vmode = info->var.vmode;
+	return err;
+}
+
 void fbcon_set_tileops(struct vc_data *vc, struct fb_info *info,
 		       struct display *p, struct fbcon_ops *ops)
 {
@@ -128,6 +140,7 @@ void fbcon_set_tileops(struct vc_data *vc, struct fb_info *info,
 	ops->putcs = tile_putcs;
 	ops->clear_margins = tile_clear_margins;
 	ops->cursor = tile_cursor;
+	ops->update_start = tile_update_start;
 
 	if (p) {
 		map.width = vc->vc_font.width;

include/linux/fb.h

@@ -201,6 +201,14 @@ struct fb_bitfield {
 #define FB_VMODE_SMOOTH_XPAN	512	/* smooth xpan possible (internally used) */
 #define FB_VMODE_CONUPDATE	512	/* don't update x/yoffset	*/
 
+/*
+ * Display rotation support
+ */
+#define FB_ROTATE_UR      0
+#define FB_ROTATE_CW      1
+#define FB_ROTATE_UD      2
+#define FB_ROTATE_CCW     3
+
 #define PICOS2KHZ(a) (1000000000UL/(a))
 #define KHZ2PICOS(a) (1000000000UL/(a))
 
@@ -489,9 +497,9 @@ struct fb_cursor_user {
 #define FB_EVENT_MODE_DELETE            0x04
 /*      A driver registered itself */
 #define FB_EVENT_FB_REGISTERED          0x05
-/*      get console to framebuffer mapping */
+/*      CONSOLE-SPECIFIC: get console to framebuffer mapping */
 #define FB_EVENT_GET_CONSOLE_MAP        0x06
-/*      set console to framebuffer mapping */
+/*      CONSOLE-SPECIFIC: set console to framebuffer mapping */
 #define FB_EVENT_SET_CONSOLE_MAP        0x07
 /*      A display blank is requested       */
 #define FB_EVENT_BLANK                  0x08