btreg.h

早期freebsd实现

/*
 * Copyright (c) 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * This software was developed by the Computer Systems Engineering group
 * at Lawrence Berkeley Laboratory under DARPA contract BG 91-66 and
 * contributed to Berkeley.
 *
 * All advertising materials mentioning features or use of this software
 * must display the following acknowledgement:
 *	This product includes software developed by the University of
 *	California, Lawrence Berkeley Laboratory.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by the University of
 *	California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *	@(#)btreg.h	8.2 (Berkeley) 1/21/94
 *
 * from: $Header: btreg.h,v 1.1 93/10/12 15:28:52 torek Exp $
 */

/*
 * Several Sun color frame buffers use some kind of Brooktree video
 * DAC (e.g., the Bt458, -- in any case, Brooktree make the only
 * decent color frame buffer chips).
 *
 * Color map control on these is a bit funky in a SPARCstation.
 * To update the color map one would normally do byte writes, but
 * the hardware takes longword writes.  Since there are three
 * registers for each color map entry (R, then G, then B), we have
 * to set color 1 with a write to address 0 (setting 0's R/G/B and
 * color 1's R) followed by a second write to address 1 (setting
 * color 1's G/B and color 2's R/G).  Software must therefore keep
 * a copy of the current map.
 *
 * The colormap address register increments automatically, so the
 * above write is done as:
 *
 *	bt->bt_addr = 0;
 *	bt->bt_cmap = R0G0B0R1;
 *	bt->bt_cmap = G1B1R2G2;
 *	...
 *
 * Yow!
 *
 * Bonus complication: on the cg6, only the top 8 bits of each 32 bit
 * register matter, even though the cg3 takes all the bits from all
 * bytes written to it.
 */
struct bt_regs {
	u_int	bt_addr;		/* map address register */
	u_int	bt_cmap;		/* colormap data register */
	u_int	bt_ctrl;		/* control register */
	u_int	bt_omap;		/* overlay (cursor) map register */
};