root/include/drm/drm_fixed.h

DEFINITIONS

1. dfixed_floor
2. dfixed_ceil
3. dfixed_div
4. drm_int2fixp
5. drm_fixp2int
6. drm_fixp_msbset
7. drm_fixp_mul
8. drm_fixp_div
9. drm_fixp_exp

/*
 * Copyright 2009 Red Hat Inc.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
 * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
 * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 * OTHER DEALINGS IN THE SOFTWARE.
 *
 * Authors: Dave Airlie
 *          Christian König
 */
#ifndef DRM_FIXED_H
#define DRM_FIXED_H

#include <linux/math64.h>

typedef union dfixed {
        u32 full;
} fixed20_12;


#define dfixed_const(A) (u32)(((A) << 12))/*  + ((B + 0.000122)*4096)) */
#define dfixed_const_half(A) (u32)(((A) << 12) + 2048)
#define dfixed_const_666(A) (u32)(((A) << 12) + 2731)
#define dfixed_const_8(A) (u32)(((A) << 12) + 3277)
#define dfixed_mul(A, B) ((u64)((u64)(A).full * (B).full + 2048) >> 12)
#define dfixed_init(A) { .full = dfixed_const((A)) }
#define dfixed_init_half(A) { .full = dfixed_const_half((A)) }
#define dfixed_trunc(A) ((A).full >> 12)
#define dfixed_frac(A) ((A).full & ((1 << 12) - 1))

static inline u32 dfixed_floor(fixed20_12 A)
{
        u32 non_frac = dfixed_trunc(A);

        return dfixed_const(non_frac);
}

static inline u32 dfixed_ceil(fixed20_12 A)
{
        u32 non_frac = dfixed_trunc(A);

        if (A.full > dfixed_const(non_frac))
                return dfixed_const(non_frac + 1);
        else
                return dfixed_const(non_frac);
}

static inline u32 dfixed_div(fixed20_12 A, fixed20_12 B)
{
        u64 tmp = ((u64)A.full << 13);

        do_div(tmp, B.full);
        tmp += 1;
        tmp /= 2;
        return lower_32_bits(tmp);
}

#define DRM_FIXED_POINT         32
#define DRM_FIXED_ONE           (1ULL << DRM_FIXED_POINT)
#define DRM_FIXED_DECIMAL_MASK  (DRM_FIXED_ONE - 1)
#define DRM_FIXED_DIGITS_MASK   (~DRM_FIXED_DECIMAL_MASK)

static inline s64 drm_int2fixp(int a)
{
        return ((s64)a) << DRM_FIXED_POINT;
}

static inline int drm_fixp2int(int64_t a)
{
        return ((s64)a) >> DRM_FIXED_POINT;
}

static inline unsigned drm_fixp_msbset(int64_t a)
{
        unsigned shift, sign = (a >> 63) & 1;

        for (shift = 62; shift > 0; --shift)
                if (((a >> shift) & 1) != sign)
                        return shift;

        return 0;
}

static inline s64 drm_fixp_mul(s64 a, s64 b)
{
        unsigned shift = drm_fixp_msbset(a) + drm_fixp_msbset(b);
        s64 result;

        if (shift > 61) {
                shift = shift - 61;
                a >>= (shift >> 1) + (shift & 1);
                b >>= shift >> 1;
        } else
                shift = 0;

        result = a * b;

        if (shift > DRM_FIXED_POINT)
                return result << (shift - DRM_FIXED_POINT);

        if (shift < DRM_FIXED_POINT)
                return result >> (DRM_FIXED_POINT - shift);

        return result;
}

static inline s64 drm_fixp_div(s64 a, s64 b)
{
        unsigned shift = 62 - drm_fixp_msbset(a);
        s64 result;

        a <<= shift;

        if (shift < DRM_FIXED_POINT)
                b >>= (DRM_FIXED_POINT - shift);

        result = div64_s64(a, b);

        if (shift > DRM_FIXED_POINT)
                return result >> (shift - DRM_FIXED_POINT);

        return result;
}

static inline s64 drm_fixp_exp(s64 x)
{
        s64 tolerance = div64_s64(DRM_FIXED_ONE, 1000000);
        s64 sum = DRM_FIXED_ONE, term, y = x;
        u64 count = 1;

        if (x < 0)
                y = -1 * x;

        term = y;

        while (term >= tolerance) {
                sum = sum + term;
                count = count + 1;
                term = drm_fixp_mul(term, div64_s64(y, count));
        }

        if (x < 0)
                sum = drm_fixp_div(DRM_FIXED_ONE, sum);

        return sum;
}

#endif