xref: /openbsd/sys/arch/luna88k/stand/boot/bmd.c (revision 684cac8d)
1 /*	$OpenBSD: bmd.c,v 1.6 2023/02/15 12:43:32 aoyama Exp $	*/
2 /*	$NetBSD: bmd.c,v 1.2 2013/01/20 13:35:43 tsutsui Exp $	*/
3 
4 /*
5  * Copyright (c) 1992 OMRON Corporation.
6  *
7  * This code is derived from software contributed to Berkeley by
8  * OMRON Corporation.
9  *
10  * Redistribution and use in source and binary forms, with or without
11  * modification, are permitted provided that the following conditions
12  * are met:
13  * 1. Redistributions of source code must retain the above copyright
14  *    notice, this list of conditions and the following disclaimer.
15  * 2. Redistributions in binary form must reproduce the above copyright
16  *    notice, this list of conditions and the following disclaimer in the
17  *    documentation and/or other materials provided with the distribution.
18  * 3. All advertising materials mentioning features or use of this software
19  *    must display the following acknowledgement:
20  *	This product includes software developed by the University of
21  *	California, Berkeley and its contributors.
22  * 4. Neither the name of the University nor the names of its contributors
23  *    may be used to endorse or promote products derived from this software
24  *    without specific prior written permission.
25  *
26  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
27  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
28  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
29  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
30  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
31  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
32  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
33  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
34  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
35  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
36  * SUCH DAMAGE.
37  *
38  *	@(#)bmd.c	8.2 (Berkeley) 8/15/93
39  */
40 /*
41  * Copyright (c) 1992, 1993
42  *	The Regents of the University of California.  All rights reserved.
43  *
44  * This code is derived from software contributed to Berkeley by
45  * OMRON Corporation.
46  *
47  * Redistribution and use in source and binary forms, with or without
48  * modification, are permitted provided that the following conditions
49  * are met:
50  * 1. Redistributions of source code must retain the above copyright
51  *    notice, this list of conditions and the following disclaimer.
52  * 2. Redistributions in binary form must reproduce the above copyright
53  *    notice, this list of conditions and the following disclaimer in the
54  *    documentation and/or other materials provided with the distribution.
55  * 3. Neither the name of the University nor the names of its contributors
56  *    may be used to endorse or promote products derived from this software
57  *    without specific prior written permission.
58  *
59  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
60  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
61  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
62  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
63  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
64  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
65  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
66  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
67  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
68  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
69  * SUCH DAMAGE.
70  *
71  *	@(#)bmd.c	8.2 (Berkeley) 8/15/93
72  */
73 /*
74 
75  * bmd.c --- Bitmap-Display raw-level driver routines
76  *
77  *	by A.Fujita, SEP-09-1992
78  */
79 
80 
81 #include <sys/param.h>
82 #include <machine/board.h>
83 #include <luna88k/stand/boot/samachdep.h>
84 
85 /*
86  *  RFCNT register
87  */
88 
89 union bmd_rfcnt {
90 	struct {
91 		short	rfc_hcnt;
92 		short	rfc_vcnt;
93 	} p;
94 	uint32_t u;
95 };
96 
97 #define isprint(c)      ((c) >= 0x20 && (c) < 0x7f)
98 
99 /*
100  *  Width & Height
101  */
102 
103 #define	PB_WIDTH	2048			/* Plane Width   (Bit) */
104 #define	PB_HEIGHT	1024			/* Plane Height  (Bit) */
105 #define PS_WIDTH	128			/* Plane Width   (Short) */
106 #define P_WIDTH		256			/* Plane Width   (Byte) */
107 
108 #define SB_WIDTH	1280			/* Screen Width  (Bit) */
109 #define	SB_HEIGHT	1024			/* Screen Height (Bit) */
110 #define SS_WIDTH	80			/* Screen Width  (Short) */
111 #define S_WIDTH		160			/* Screen Width  (Byte) */
112 
113 #define FB_WIDTH	12			/* Font Width    (Bit) */
114 #define FB_HEIGHT	20			/* Font Height   (Bit) */
115 
116 
117 #define NEXT_LINE(addr)			((addr) + (PS_WIDTH * FB_HEIGHT))
118 #define SKIP_NEXT_LINE(addr)		(addr) += (PS_WIDTH - SS_WIDTH)
119 
120 
121 void	bmd_draw_char(char *, char *, int, int, int);
122 void	bmd_reverse_char(char *, char *, int, int);
123 void	bmd_erase_char(char *, char *, int, int);
124 void	bmd_erase_screen(volatile u_short *);
125 void	bmd_scroll_screen(volatile u_short *, volatile u_short *,
126 	    int, int, int, int);
127 
128 
129 struct bmd_linec {
130 	struct bmd_linec *bl_next;
131 	struct bmd_linec *bl_prev;
132 	int	bl_col;
133 	int	bl_end;
134 	u_char	bl_line[128];
135 };
136 
137 struct bmd_softc {
138 	int	bc_stat;
139 	char   *bc_raddr;
140 	char   *bc_waddr;
141 	int	bc_xmin;
142 	int	bc_xmax;
143 	int	bc_ymin;
144 	int	bc_ymax;
145 	int	bc_col;
146 	int	bc_row;
147 	struct bmd_linec *bc_bl;
148 	char	bc_escseq[8];
149 	char   *bc_esc;
150 	void  (*bc_escape)(int);
151 };
152 
153 #define	STAT_NORMAL	0x0000
154 #define	STAT_ESCAPE	0x0001
155 #define	STAT_INSERT	0x0100
156 
157 struct	bmd_softc bmd_softc;
158 struct	bmd_linec bmd_linec[52];
159 
160 void	bmd_escape(int);
161 void	bmd_escape_0(int);
162 void	bmd_escape_1(int);
163 
164 
165 /*
166  * Escape-Sequence
167  */
168 
169 void
bmd_escape(int c)170 bmd_escape(int c)
171 {
172 	struct bmd_softc *bp = &bmd_softc;
173 
174 	switch (c) {
175 
176 	case '[':
177 		bp->bc_escape = bmd_escape_0;
178 		break;
179 
180 	default:
181 		bp->bc_stat &= ~STAT_ESCAPE;
182 		bp->bc_esc = &bp->bc_escseq[0];
183 		bp->bc_escape = bmd_escape;
184 		break;
185 	}
186 }
187 
188 void
bmd_escape_0(int c)189 bmd_escape_0(int c)
190 {
191 	struct bmd_softc *bp = &bmd_softc;
192 	struct bmd_linec *bq = bp->bc_bl;
193 
194 	switch (c) {
195 
196 	case 'A':
197 		if (bp->bc_row > bp->bc_ymin) {
198 			bp->bc_row--;
199 		}
200 		break;
201 
202 	case 'C':
203 		if (bq->bl_col < bp->bc_xmax - 1) {
204 			bq->bl_col++;
205 		}
206 		break;
207 
208 	case 'K':
209 		if (bq->bl_col < bp->bc_xmax) {
210 			int col;
211 			for (col = bq->bl_col; col < bp->bc_xmax; col++)
212 				bmd_erase_char(bp->bc_raddr,
213 					       bp->bc_waddr,
214 					       col, bp->bc_row);
215 		}
216 		bq->bl_end = bq->bl_col;
217 		break;
218 
219 	case 'H':
220 		bq->bl_col = bq->bl_end = bp->bc_xmin;
221 		bp->bc_row = bp->bc_ymin;
222 		break;
223 
224 	default:
225 /*
226 		*bp->bc_esc++ = c;
227 		bp->bc_escape = bmd_escape_1;
228 		return;
229  */
230 		break;
231 	}
232 
233 	bp->bc_stat &= ~STAT_ESCAPE;
234 	bp->bc_esc = &bp->bc_escseq[0];
235 	bp->bc_escape = bmd_escape;
236 }
237 
238 void
bmd_escape_1(int c)239 bmd_escape_1(int c)
240 {
241 	struct bmd_softc *bp = &bmd_softc;
242 	struct bmd_linec *bq = bp->bc_bl;
243 	int col = 0, row = 0;
244 	char *p;
245 
246 	switch (c) {
247 
248 	case 'J':
249 		bp->bc_stat &= ~STAT_ESCAPE;
250 		bp->bc_esc = &bp->bc_escseq[0];
251 		bp->bc_escape = bmd_escape;
252 		break;
253 
254 	case 'H':
255 		for (p = &bp->bc_escseq[0]; *p != ';'; p++)
256 			row = (row * 10) + (*p - 0x30);
257 		p++;
258 		for (p = &bp->bc_escseq[0]; p != bp->bc_esc; p++)
259 			col = (col * 10) + (*p - 0x30);
260 
261 		bq->bl_col = col + bp->bc_xmin;
262 		bp->bc_row = row + bp->bc_ymin;
263 
264 		bp->bc_stat &= ~STAT_ESCAPE;
265 		bp->bc_esc = &bp->bc_escseq[0];
266 		bp->bc_escape = bmd_escape;
267 		break;
268 
269 	default:
270 		*bp->bc_esc++ = c;
271 		break;
272 	}
273 }
274 
275 
276 /*
277  * Entry Routine
278  */
279 
280 void
bmdinit(void)281 bmdinit(void)
282 {
283 	volatile uint32_t *bmd_rfcnt = (volatile uint32_t *)BMAP_RFCNT;
284 	volatile long *bmd_bmsel = (volatile long *)BMAP_BMSEL;
285 	struct bmd_softc *bp = &bmd_softc;
286 	struct bmd_linec *bq;
287 	int i;
288 	union bmd_rfcnt rfcnt;
289 
290 	/*
291 	 *  adjust plane position
292 	 */
293 
294 	bp->bc_raddr = (char *)(BMAP_BMAP0 + 8);	/* plane-0 hardware address */
295 	bp->bc_waddr = (char *)(BMAP_BMP + 8);		/* common bitmap hardware address */
296 	rfcnt.p.rfc_hcnt = 7;				/* shift left   16 dot */
297 	rfcnt.p.rfc_vcnt = -27;				/* shift down    1 dot */
298 	*bmd_rfcnt = rfcnt.u;
299 
300 	bp->bc_stat  = STAT_NORMAL;
301 
302 	bp->bc_xmin  = 12;
303 	bp->bc_xmax  = 92;
304 	bp->bc_ymin  = 2;
305 	bp->bc_ymax  = 48;
306 
307 	bp->bc_row = bp->bc_ymin;
308 
309 	for (i = bp->bc_ymin; i < bp->bc_ymax; i++) {
310 		bmd_linec[i].bl_next = &bmd_linec[i+1];
311 		bmd_linec[i].bl_prev = &bmd_linec[i-1];
312 	}
313 	bmd_linec[bp->bc_ymax-1].bl_next = &bmd_linec[bp->bc_ymin];
314 	bmd_linec[bp->bc_ymin].bl_prev = &bmd_linec[bp->bc_ymax-1];
315 
316 	bq = bp->bc_bl = &bmd_linec[bp->bc_ymin];
317 	bq->bl_col = bq->bl_end = bp->bc_xmin;
318 
319 	bp->bc_col = bp->bc_xmin;
320 
321 	bp->bc_esc = &bp->bc_escseq[0];
322 	bp->bc_escape = bmd_escape;
323 
324 	*bmd_bmsel = 0xff;				/* all planes */
325 	bmd_erase_screen((u_short *) bp->bc_waddr);	/* clear screen */
326 	*bmd_bmsel = 0x01;				/* 1 plane */
327 
328 							/* turn on  cursole */
329 	bmd_reverse_char(bp->bc_raddr,
330 			 bp->bc_waddr,
331 			 bq->bl_col, bp->bc_row);
332 }
333 
334 void
bmdadjust(short hcnt,short vcnt)335 bmdadjust(short hcnt, short vcnt)
336 {
337 	volatile uint32_t *bmd_rfcnt = (volatile uint32_t *)BMAP_RFCNT;
338 	union bmd_rfcnt rfcnt;
339 
340 	printf("bmdadjust: hcnt = %d, vcnt = %d\n", hcnt, vcnt);
341 
342 	rfcnt.p.rfc_hcnt = hcnt;		/* shift left   16 dot */
343 	rfcnt.p.rfc_vcnt = vcnt;		/* shift down    1 dot */
344 
345 	*bmd_rfcnt = rfcnt.u;
346 }
347 
348 int
bmdputc(int c)349 bmdputc(int c)
350 {
351 	struct bmd_softc *bp = &bmd_softc;
352 	struct bmd_linec *bq = bp->bc_bl;
353 	int i;
354 
355 	c &= 0x7F;
356 							/* turn off cursole */
357 	bmd_reverse_char(bp->bc_raddr,
358 			 bp->bc_waddr,
359 			 bq->bl_col, bp->bc_row);
360 							/* do escape-sequence */
361 	if (bp->bc_stat & STAT_ESCAPE) {
362 		*bp->bc_esc++ = c;
363 		(*bp->bc_escape)(c);
364 		goto done;
365 	}
366 
367 	if (isprint(c)) {
368 		bmd_draw_char(bp->bc_raddr, bp->bc_waddr,
369 			      bq->bl_col, bp->bc_row, c);
370 		bq->bl_col++;
371 		bq->bl_end++;
372 		if (bq->bl_col >= bp->bc_xmax) {
373 			bq->bl_col = bq->bl_end = bp->bc_xmin;
374 			bp->bc_row++;
375 			if (bp->bc_row >= bp->bc_ymax) {
376 				bmd_scroll_screen((u_short *) bp->bc_raddr,
377 						  (u_short *) bp->bc_waddr,
378 						  bp->bc_xmin, bp->bc_xmax,
379 						  bp->bc_ymin, bp->bc_ymax);
380 
381 				bp->bc_row = bp->bc_ymax - 1;
382 			}
383 		}
384 	} else {
385 		switch (c) {
386 		case 0x08:				/* BS */
387 			if (bq->bl_col > bp->bc_xmin) {
388 				bq->bl_col--;
389 			}
390 			break;
391 
392 		case 0x09:				/* HT */
393 		case 0x0B:				/* VT */
394 			i = ((bq->bl_col / 8) + 1) * 8;
395 			if (i < bp->bc_xmax) {
396 				bq->bl_col = bq->bl_end = i;
397 			}
398 			break;
399 
400 		case 0x0A:				/* NL */
401 			bp->bc_row++;
402 			if (bp->bc_row >= bp->bc_ymax) {
403 				bmd_scroll_screen((u_short *) bp->bc_raddr,
404 						  (u_short *) bp->bc_waddr,
405 						  bp->bc_xmin, bp->bc_xmax,
406 						  bp->bc_ymin, bp->bc_ymax);
407 
408 				bp->bc_row = bp->bc_ymax - 1;
409 			}
410 			break;
411 
412 		case 0x0D:				/* CR */
413 			bq->bl_col = bp->bc_xmin;
414 			break;
415 
416 		case 0x1b:				/* ESC */
417 			bp->bc_stat |= STAT_ESCAPE;
418 			*bp->bc_esc++ = 0x1b;
419 			break;
420 
421 		case 0x7F:				/* DEL */
422 			if (bq->bl_col > bp->bc_xmin) {
423 				bq->bl_col--;
424 				bmd_erase_char(bp->bc_raddr,
425 					       bp->bc_waddr,
426 					       bq->bl_col, bp->bc_row);
427 			}
428 			break;
429 
430 		default:
431 			break;
432 		}
433 	}
434 
435  done:
436 							/* turn on  cursole */
437 	bmd_reverse_char(bp->bc_raddr,
438 			 bp->bc_waddr,
439 			 bq->bl_col, bp->bc_row);
440 
441 	return(c);
442 }
443 
444 void
bmdclear(void)445 bmdclear(void)
446 {
447 	struct bmd_softc *bp = &bmd_softc;
448 	struct bmd_linec *bq = bp->bc_bl;
449 
450 	bmd_erase_screen((u_short *) bp->bc_waddr);	/* clear screen */
451 
452 	bq->bl_col = bq->bl_end = bp->bc_xmin;
453 	bp->bc_row = bp->bc_ymin;
454 
455 	bmd_reverse_char(bp->bc_raddr,
456 			 bp->bc_waddr,
457 			 bq->bl_col, bp->bc_row);	/* turn on  cursole */
458 }
459 
460 
461 /*
462  *  character operation routines
463  */
464 
465 void
bmd_draw_char(char * raddr,char * waddr,int col,int row,int c)466 bmd_draw_char(char *raddr, char *waddr, int col, int row, int c)
467 {
468 	volatile u_short *p, *q;
469 	const u_short *fp;
470 	int i;
471 
472 	fp = &bmdfont[c][0];
473 
474 	switch (col % 4) {
475 
476 	case 0:
477 		p = (u_short *) ( raddr + (( row * FB_HEIGHT ) << 8 ) + (( col / 4 ) * 6 ));
478 		q = (u_short *) ( waddr + (( row * FB_HEIGHT ) << 8 ) + (( col / 4 ) * 6 ));
479 		for (i = 0; i < FB_HEIGHT; i++) {
480 			*q = (*p & 0x000F) | (*fp & 0xFFF0);
481 			p += 128;
482 			q += 128;
483 			fp++;
484 		}
485 		break;
486 
487 	case 1:
488 		p = (u_short *) ( raddr + (( row * FB_HEIGHT ) << 8 ) + (( col / 4 ) * 6 ));
489 		q = (u_short *) ( waddr + (( row * FB_HEIGHT ) << 8 ) + (( col / 4 ) * 6 ));
490 		for (i = 0; i < FB_HEIGHT; i++) {
491 			q[0] = (p[0] & 0xFFF0) | ((*fp & 0xF000) >> 12);
492 			q[1] = (p[1] & 0x00FF) | ((*fp & 0x0FF0) << 4);
493 			p += 128;
494 			q += 128;
495 			fp++;
496 		}
497 		break;
498 
499 	case 2:
500 		p = (u_short *) ( raddr + (( row * FB_HEIGHT ) << 8 ) + (( col / 4 ) * 6 ) + 2 );
501 		q = (u_short *) ( waddr + (( row * FB_HEIGHT ) << 8 ) + (( col / 4 ) * 6 ) + 2 );
502 		for (i = 0; i < FB_HEIGHT; i++) {
503 			q[0] = (p[0] & 0xFF00) | ((*fp & 0xFF00) >> 8);
504 			q[1] = (p[1] & 0x0FFF) | ((*fp & 0x00F0) << 8);
505 			p += 128;
506 			q += 128;
507 			fp++;
508 		}
509 		break;
510 
511 	case 3:
512 		p = (u_short *) ( raddr + (( row * FB_HEIGHT ) << 8 ) + (( col / 4 ) * 6 ) + 4 );
513 		q = (u_short *) ( waddr + (( row * FB_HEIGHT ) << 8 ) + (( col / 4 ) * 6 ) + 4 );
514 		for (i = 0; i < FB_HEIGHT; i++) {
515 			*q = (*p & 0xF000) | ((*fp & 0xFFF0) >> 4);
516 			p += 128;
517 			q += 128;
518 			fp++;
519 		}
520 		break;
521 
522 	default:
523 		break;
524 	}
525 }
526 
527 void
bmd_reverse_char(char * raddr,char * waddr,int col,int row)528 bmd_reverse_char(char *raddr, char *waddr, int col, int row)
529 {
530 	volatile u_short *p, *q;
531 	int i;
532 
533 	switch (col%4) {
534 
535 	case 0:
536 		p = (u_short *) ( raddr + (( row * FB_HEIGHT ) << 8 ) + (( col / 4 ) * 6 ));
537 		q = (u_short *) ( waddr + (( row * FB_HEIGHT ) << 8 ) + (( col / 4 ) * 6 ));
538 		for (i = 0; i < FB_HEIGHT; i++) {
539 			*q = (*p & 0x000F) | (~(*p) & 0xFFF0);
540 			p += 128;
541 			q += 128;
542 		}
543 		break;
544 
545 	case 1:
546 		p = (u_short *) ( raddr + (( row * FB_HEIGHT ) << 8 ) + (( col / 4 ) * 6 ));
547 		q = (u_short *) ( waddr + (( row * FB_HEIGHT ) << 8 ) + (( col / 4 ) * 6 ));
548 		for (i = 0; i < FB_HEIGHT; i++) {
549 			q[0] = (p[0] & 0xFFF0) | (~p[0] & 0x000F);
550 			q[1] = (p[1] & 0x00FF) | (~p[1] & 0xFF00);
551 			p += 128;
552 			q += 128;
553 		}
554 		break;
555 
556 	case 2:
557 		p = (u_short *) ( raddr + (( row * FB_HEIGHT ) << 8 ) + (( col / 4 ) * 6 ) + 2 );
558 		q = (u_short *) ( waddr + (( row * FB_HEIGHT ) << 8 ) + (( col / 4 ) * 6 ) + 2 );
559 		for (i = 0; i < FB_HEIGHT; i++) {
560 			q[0] = (p[0] & 0xFF00) | (~p[0] & 0x00FF);
561 			q[1] = (p[1] & 0x0FFF) | (~p[1] & 0xF000);
562 			p += 128;
563 			q += 128;
564 		}
565 		break;
566 
567 	case 3:
568 		p = (u_short *) ( raddr + (( row * FB_HEIGHT ) << 8 ) + (( col / 4 ) * 6 ) + 4 );
569 		q = (u_short *) ( waddr + (( row * FB_HEIGHT ) << 8 ) + (( col / 4 ) * 6 ) + 4 );
570 		for (i = 0; i < FB_HEIGHT; i++) {
571 			*q = (*p & 0xF000) | (~(*p) & 0x0FFF);
572 			p += 128;
573 			q += 128;
574 		}
575 		break;
576 
577 	default:
578 		break;
579 	}
580 }
581 
582 void
bmd_erase_char(char * raddr,char * waddr,int col,int row)583 bmd_erase_char(char *raddr, char *waddr, int col, int row)
584 {
585 	bmd_draw_char(raddr, waddr, col, row, 0);
586 
587 	return;
588 }
589 
590 
591 /*
592  * screen operation routines
593  */
594 
595 void
bmd_erase_screen(volatile u_short * p)596 bmd_erase_screen(volatile u_short *p)
597 {
598 	int i, j;
599 
600 	for (i = 0; i < SB_HEIGHT; i++) {
601 		for (j = 0; j < SS_WIDTH; j++)
602 			*p++ = 0;
603 		SKIP_NEXT_LINE(p);
604 	}
605 
606 	return;
607 }
608 
609 void
bmd_scroll_screen(volatile u_short * p,volatile u_short * q,int xmin,int xmax,int ymin,int ymax)610 bmd_scroll_screen(volatile u_short *p, volatile u_short *q,
611     int xmin, int xmax, int ymin, int ymax)
612 {
613 	int i, j;
614 
615 	p += ((PS_WIDTH * FB_HEIGHT) * (ymin + 1));
616 	q += ((PS_WIDTH * FB_HEIGHT) *  ymin);
617 
618 	for (i = 0; i < ((ymax - ymin -1) * FB_HEIGHT); i++) {
619 		for (j = 0; j < SS_WIDTH; j++) {
620 			*q++ = *p++;
621 		}
622 		p += (PS_WIDTH - SS_WIDTH);
623 		q += (PS_WIDTH - SS_WIDTH);
624 	}
625 
626 	for (i = 0; i < FB_HEIGHT; i++) {
627 		for (j = 0; j < SS_WIDTH; j++) {
628 			*q++ = 0;
629 		}
630 		q += (PS_WIDTH - SS_WIDTH);
631 	}
632 
633 }
634