diff options
Diffstat (limited to 'drivers/gpu/drm/drm_color_mgmt.c')
| -rw-r--r-- | drivers/gpu/drm/drm_color_mgmt.c | 40 |
1 files changed, 25 insertions, 15 deletions
diff --git a/drivers/gpu/drm/drm_color_mgmt.c b/drivers/gpu/drm/drm_color_mgmt.c index 4ce5c6d8de99..c93123ff7c21 100644 --- a/drivers/gpu/drm/drm_color_mgmt.c +++ b/drivers/gpu/drm/drm_color_mgmt.c @@ -109,28 +109,38 @@ */ /** - * drm_color_lut_extract - clamp and round LUT entries + * drm_color_ctm_s31_32_to_qm_n + * * @user_input: input value - * @bit_precision: number of bits the hw LUT supports + * @m: number of integer bits, only support m <= 32, include the sign-bit + * @n: number of fractional bits, only support n <= 32 + * + * Convert and clamp S31.32 sign-magnitude to Qm.n (signed 2's complement). + * The sign-bit BIT(m+n-1) and above are 0 for positive value and 1 for negative + * the range of value is [-2^(m-1), 2^(m-1) - 2^-n] + * + * For example + * A Q3.12 format number: + * - required bit: 3 + 12 = 15bits + * - range: [-2^2, 2^2 - 2^−15] * - * Extract a degamma/gamma LUT value provided by user (in the form of - * &drm_color_lut entries) and round it to the precision supported by the - * hardware. + * NOTE: the m can be zero if all bit_precision are used to present fractional + * bits like Q0.32 */ -uint32_t drm_color_lut_extract(uint32_t user_input, uint32_t bit_precision) +u64 drm_color_ctm_s31_32_to_qm_n(u64 user_input, u32 m, u32 n) { - uint32_t val = user_input; - uint32_t max = 0xffff >> (16 - bit_precision); + u64 mag = (user_input & ~BIT_ULL(63)) >> (32 - n); + bool negative = !!(user_input & BIT_ULL(63)); + s64 val; - /* Round only if we're not using full precision. */ - if (bit_precision < 16) { - val += 1UL << (16 - bit_precision - 1); - val >>= 16 - bit_precision; - } + WARN_ON(m > 32 || n > 32); + + val = clamp_val(mag, 0, negative ? + BIT_ULL(n + m - 1) : BIT_ULL(n + m - 1) - 1); - return clamp_val(val, 0, max); + return negative ? -val : val; } -EXPORT_SYMBOL(drm_color_lut_extract); +EXPORT_SYMBOL(drm_color_ctm_s31_32_to_qm_n); /** * drm_crtc_enable_color_mgmt - enable color management properties |