1 /* 2 * Copyright (c) 1993 3 * The Regents of the University of California. All rights reserved. 4 * 5 * This software was developed by the Computer Systems Engineering group 6 * at Lawrence Berkeley Laboratory under DARPA contract BG 91-66 and 7 * contributed to Berkeley. 8 * 9 * All advertising materials mentioning features or use of this software 10 * must display the following acknowledgement: 11 * This product includes software developed by the University of 12 * California, Lawrence Berkeley Laboratory. 13 * 14 * %sccs.include.redist.c% 15 * 16 * @(#)btreg.h 8.2 (Berkeley) 01/21/94 17 * 18 * from: $Header: btreg.h,v 1.1 93/10/12 15:28:52 torek Exp $ 19 */ 20 21 /* 22 * Several Sun color frame buffers use some kind of Brooktree video 23 * DAC (e.g., the Bt458, -- in any case, Brooktree make the only 24 * decent color frame buffer chips). 25 * 26 * Color map control on these is a bit funky in a SPARCstation. 27 * To update the color map one would normally do byte writes, but 28 * the hardware takes longword writes. Since there are three 29 * registers for each color map entry (R, then G, then B), we have 30 * to set color 1 with a write to address 0 (setting 0's R/G/B and 31 * color 1's R) followed by a second write to address 1 (setting 32 * color 1's G/B and color 2's R/G). Software must therefore keep 33 * a copy of the current map. 34 * 35 * The colormap address register increments automatically, so the 36 * above write is done as: 37 * 38 * bt->bt_addr = 0; 39 * bt->bt_cmap = R0G0B0R1; 40 * bt->bt_cmap = G1B1R2G2; 41 * ... 42 * 43 * Yow! 44 * 45 * Bonus complication: on the cg6, only the top 8 bits of each 32 bit 46 * register matter, even though the cg3 takes all the bits from all 47 * bytes written to it. 48 */ 49 struct bt_regs { 50 u_int bt_addr; /* map address register */ 51 u_int bt_cmap; /* colormap data register */ 52 u_int bt_ctrl; /* control register */ 53 u_int bt_omap; /* overlay (cursor) map register */ 54 }; 55