fbdev: advertise limitation of drawing engine

A few drivers are not capable of blitting rectangles of any dimension.
vga16fb can only blit 8-pixel wide rectangles, while s3fb (in tileblitting
mode) can only blit 8x16 rectangles.  For example, loading a 12x22 font in
vga16fb will result in a corrupt display.

Advertise this limitation/capability in info->pixmap.blit_x and blit_y.  These
fields are 32-bit arrays (font max is 32x32 only), ie, if bit 7 is set, then
width/height of 7+1 is supported.
Signed-off-by: Antonino Daplas <adaplas@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/video/fbmem.c

@@ -1321,6 +1321,12 @@ register_framebuffer(struct fb_info *fb_info)
 	}	
 	fb_info->pixmap.offset = 0;
 
+	if (!fb_info->pixmap.blit_x)
+		fb_info->pixmap.blit_x = ~(u32)0;
+
+	if (!fb_info->pixmap.blit_y)
+		fb_info->pixmap.blit_y = ~(u32)0;
+
 	if (!fb_info->modelist.prev || !fb_info->modelist.next)
 		INIT_LIST_HEAD(&fb_info->modelist);
 

include/linux/fb.h

@@ -558,6 +558,10 @@ struct fb_pixmap {
 	u32 scan_align;		/* alignment per scanline		*/
 	u32 access_align;	/* alignment per read/write (bits)	*/
 	u32 flags;		/* see FB_PIXMAP_*			*/
+	u32 blit_x;             /* supported bit block dimensions (1-32)*/
+	u32 blit_y;             /* Format: blit_x = 1 << (width - 1)    */
+	                        /*         blit_y = 1 << (height - 1)   */
+	                        /* if 0, will be set to 0xffffffff (all)*/
 	/* access methods */
 	void (*writeio)(struct fb_info *info, void __iomem *dst, void *src, unsigned int size);
 	void (*readio) (struct fb_info *info, void *dst, void __iomem *src, unsigned int size);