atiwonderio.c revision 32b578d3 
1/*
2 * Copyright 2000 through 2004 by Marc Aurele La France (TSI @ UQV), tsi@xfree86.org
3 *
4 * Permission to use, copy, modify, distribute, and sell this software and its
5 * documentation for any purpose is hereby granted without fee, provided that
6 * the above copyright notice appear in all copies and that both that copyright
7 * notice and this permission notice appear in supporting documentation, and
8 * that the name of Marc Aurele La France not be used in advertising or
9 * publicity pertaining to distribution of the software without specific,
10 * written prior permission.  Marc Aurele La France makes no representations
11 * about the suitability of this software for any purpose.  It is provided
12 * "as-is" without express or implied warranty.
13 *
14 * MARC AURELE LA FRANCE DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
15 * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS.  IN NO
16 * EVENT SHALL MARC AURELE LA FRANCE BE LIABLE FOR ANY SPECIAL, INDIRECT OR
17 * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE,
18 * DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
19 * TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
20 * PERFORMANCE OF THIS SOFTWARE.
21 */
22
23#ifdef HAVE_CONFIG_H
24#include "config.h"
25#endif
26
27#include "ati.h"
28#include "atichip.h"
29#include "atiwonderio.h"
30
31#ifndef AVOID_CPIO
32
33/*
34 * ATIModifyExtReg --
35 *
36 * This function is called to modify certain bits in an ATI extended VGA
37 * register while preserving its other bits.  The function will not write the
38 * register if it turns out its value would not change.  This helps prevent
39 * server hangs on older adapters.
40 */
41void
42ATIModifyExtReg
43(
44    ATIPtr      pATI,
45    const CARD8 Index,
46    int         CurrentValue,
47    const CARD8 CurrentMask,
48    CARD8       NewValue
49)
50{
51    /* Possibly retrieve the current value */
52    if (CurrentValue < 0)
53        CurrentValue = ATIGetExtReg(Index);
54
55    /* Compute new value */
56    NewValue &= (CARD8)(~CurrentMask);
57    NewValue |= CurrentValue & CurrentMask;
58
59    /* Check if value will be changed */
60    if (CurrentValue == NewValue)
61        return;
62
63        ATIPutExtReg(Index, NewValue);
64}
65
66#endif /* AVOID_CPIO */
67