PERFORCE change 76704 for review

[Marcel Moolenaar]

http://perforce.freebsd.org/chv.cgi?CH=76704

Change 76704 by marcel at marcel_nfs on 2005/05/08 19:54:21

	Wordsmithing after proofreading. Add a reference to R.F. Ferraro's
	"Programmer's guide to the galaxy^WEGA, VGA, and Super VGA cards".

Affected files ...

.. //depot/projects/tty/sys/dev/ic/vga.h#3 edit

Differences ...

==== //depot/projects/tty/sys/dev/ic/vga.h#3 (text+ko) ====

@@ -31,15 +31,20 @@
 
 /*
  * The VGA adapter uses two I/O port blocks. One of these blocks, the CRT
- * controller registers can be located either at 0x3B0 or at 0x3D0 in I/O
+ * controller registers, can be located either at 0x3B0 or at 0x3D0 in I/O
  * port space. This allows compatibility with the monochrome adapter, which
- * as the CRT controller at 0x3B0.
+ * has the CRT controller registers at 0x3B0.
  *
  * It is assumed that compatibility with the monochrome adapter is not of
- * interest anymore. As such, the CRT controller is located at 0x3D0 in I/O
- * port space. This means that the 2 I/O blocks are adjacent in I/O port
- * space and can therefore be treated as a single logical I/O port block.
- * This simplifies matters.
+ * interest anymore. As such, the CRT controller can be located at 0x3D0 in
+ * I/O port space unconditionally. This means that the 2 I/O blocks are
+ * always adjacent and can therefore be treated as a single logical I/O port
+ * range. In practical terms: there only has to be a single tag and handle
+ * to access all registers.
+ *
+ * The following definitions are taken from or inspired by:
+ *   Programmer's Guide to the EGA, VGA, and Super VGA Cards -- 3rd ed.,
+ *     Richard F. Ferraro, Addison-Wesley, ISBN 0-201-62490-7
  */
 
 #define	VGA_MEM_BASE	0xA0000