From: "james qian wang (Arm Technology China)" <james.qian.wang@arm.com> To: Ilia Mirkin <imirkin@alum.mit.edu> Cc: Liviu Dudau <Liviu.Dudau@arm.com>, "airlied@linux.ie" <airlied@linux.ie>, Brian Starkey <Brian.Starkey@arm.com>, "maarten.lankhorst@linux.intel.com" <maarten.lankhorst@linux.intel.com>, "sean@poorly.run" <sean@poorly.run>, "Jonathan Chai (Arm Technology China)" <Jonathan.Chai@arm.com>, "Julien Yin (Arm Technology China)" <Julien.Yin@arm.com>, "Thomas Sun (Arm Technology China)" <thomas.Sun@arm.com>, "Lowry Li (Arm Technology China)" <Lowry.Li@arm.com>, Ayan Halder <Ayan.Halder@arm.com>, "Tiannan Zhu (Arm Technology China)" <Tiannan.Zhu@arm.com>, "Yiqi Kang (Arm Technology China)" <Yiqi.Kang@arm.com>, nd <nd@arm.com>, "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>, "dri-devel@lists.freedesktop.org" <dri-devel@lists.freedesktop.org>, Ben Davis <Ben.Davis@arm.com>, "Oscar Zhang (Arm Technology China)" <Oscar.Zhang@arm.com>, "Channing Chen (Arm Technology China)" <Channing.Chen@arm.com>, Mihail Atanassov <Mihail.Atanassov@arm.com> Subject: Re: [PATCH v2 1/4] drm/komeda: Add a new helper drm_color_ctm_s31_32_to_qm_n() Date: Tue, 15 Oct 2019 08:04:26 +0000 [thread overview] Message-ID: <20191015080420.GA22242@jamwan02-TSP300> (raw) In-Reply-To: <CAKb7Uvh7y20oikYR+UpabgXLHJM2i+2DPVyYSwE37d=NpheUGg@mail.gmail.com> On Mon, Oct 14, 2019 at 11:48:38PM -0400, Ilia Mirkin wrote: > On Mon, Oct 14, 2019 at 9:16 PM james qian wang (Arm Technology China) > <james.qian.wang@arm.com> wrote: > > On Mon, Oct 14, 2019 at 11:58:48AM -0400, Ilia Mirkin wrote: > > > On Fri, Oct 11, 2019 at 1:43 AM james qian wang (Arm Technology China) > > > <james.qian.wang@arm.com> wrote: > > > > + * > > > > + * Convert and clamp S31.32 sign-magnitude to Qm.n 2's complement. > > > > + */ > > > > +uint64_t drm_color_ctm_s31_32_to_qm_n(uint64_t user_input, > > > > + uint32_t m, uint32_t n) > > > > +{ > > > > + u64 mag = (user_input & ~BIT_ULL(63)) >> (32 - n); > > > > + bool negative = !!(user_input & BIT_ULL(63)); > > > > + s64 val; > > > > + > > > > + /* the range of signed 2s complement is [-2^n+m, 2^n+m - 1] */ > > > > > > This implies that n = 32, m = 0 would actually yield a 33-bit 2's > > > complement number. Is that what you meant? > > > > Yes, since m doesn't include sign-bit So a Q0.32 is a 33bit value. > > This goes counter to what the wikipedia page says [ > https://en.wikipedia.org/wiki/Q_(number_format) ]: > > (reformatted slightly for text-only consumption): > > """ > For example, a Q15.1 format number: > > - requires 15+1 = 16 bits > - its range is [-2^14, 2^14 - 2^-1] = [-16384.0, +16383.5] = [0x8000, > 0x8001 ... 0xFFFF, 0x0000, 0x0001 ... 0x7FFE, 0x7FFF] > - its resolution is 2^-1 = 0.5 > """ > > This suggests that the proper way to represent a standard 32-bit 2's > complement integer would be Q32.0. > Yes you're right, I will send a new version to correct this code according to the Wiki. Thanks James > -ilia
WARNING: multiple messages have this Message-ID (diff)
From: "james qian wang (Arm Technology China)" <james.qian.wang@arm.com> To: Ilia Mirkin <imirkin@alum.mit.edu> Cc: Liviu Dudau <Liviu.Dudau@arm.com>, "airlied@linux.ie" <airlied@linux.ie>, Brian Starkey <Brian.Starkey@arm.com>, "maarten.lankhorst@linux.intel.com" <maarten.lankhorst@linux.intel.com>, "sean@poorly.run" <sean@poorly.run>, "Jonathan Chai (Arm Technology China)" <Jonathan.Chai@arm.com>, "Julien Yin (Arm Technology China)" <Julien.Yin@arm.com>, "Thomas Sun (Arm Technology China)" <thomas.Sun@arm.com>, "Lowry Li (Arm Technology China)" <Lowry.Li@arm.com>, Ayan Halder <Ayan.Halder@arm.com>, "Tiannan Zhu (Arm Technology China)" <Tiannan.Zhu@arm.com>, "Yiqi Kang (Arm Technology China)" <Yiqi.Kang@arm.com>, nd <nd@arm.com>, "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>, "dri-devel@lists.freedesktop.org" <dri-devel@lists.freedesktop.org>, Ben Subject: Re: [PATCH v2 1/4] drm/komeda: Add a new helper drm_color_ctm_s31_32_to_qm_n() Date: Tue, 15 Oct 2019 08:04:26 +0000 [thread overview] Message-ID: <20191015080420.GA22242@jamwan02-TSP300> (raw) In-Reply-To: <CAKb7Uvh7y20oikYR+UpabgXLHJM2i+2DPVyYSwE37d=NpheUGg@mail.gmail.com> On Mon, Oct 14, 2019 at 11:48:38PM -0400, Ilia Mirkin wrote: > On Mon, Oct 14, 2019 at 9:16 PM james qian wang (Arm Technology China) > <james.qian.wang@arm.com> wrote: > > On Mon, Oct 14, 2019 at 11:58:48AM -0400, Ilia Mirkin wrote: > > > On Fri, Oct 11, 2019 at 1:43 AM james qian wang (Arm Technology China) > > > <james.qian.wang@arm.com> wrote: > > > > + * > > > > + * Convert and clamp S31.32 sign-magnitude to Qm.n 2's complement. > > > > + */ > > > > +uint64_t drm_color_ctm_s31_32_to_qm_n(uint64_t user_input, > > > > + uint32_t m, uint32_t n) > > > > +{ > > > > + u64 mag = (user_input & ~BIT_ULL(63)) >> (32 - n); > > > > + bool negative = !!(user_input & BIT_ULL(63)); > > > > + s64 val; > > > > + > > > > + /* the range of signed 2s complement is [-2^n+m, 2^n+m - 1] */ > > > > > > This implies that n = 32, m = 0 would actually yield a 33-bit 2's > > > complement number. Is that what you meant? > > > > Yes, since m doesn't include sign-bit So a Q0.32 is a 33bit value. > > This goes counter to what the wikipedia page says [ > https://en.wikipedia.org/wiki/Q_(number_format) ]: > > (reformatted slightly for text-only consumption): > > """ > For example, a Q15.1 format number: > > - requires 15+1 = 16 bits > - its range is [-2^14, 2^14 - 2^-1] = [-16384.0, +16383.5] = [0x8000, > 0x8001 ... 0xFFFF, 0x0000, 0x0001 ... 0x7FFE, 0x7FFF] > - its resolution is 2^-1 = 0.5 > """ > > This suggests that the proper way to represent a standard 32-bit 2's > complement integer would be Q32.0. > Yes you're right, I will send a new version to correct this code according to the Wiki. Thanks James > -ilia
next prev parent reply other threads:[~2019-10-15 8:04 UTC|newest] Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top 2019-10-11 5:43 [PATCH v2 0/4] drm/komeda: Enable CRTC color-mgmt james qian wang (Arm Technology China) 2019-10-11 5:43 ` james qian wang (Arm Technology China) 2019-10-11 5:43 ` [PATCH v2 1/4] drm/komeda: Add a new helper drm_color_ctm_s31_32_to_qm_n() james qian wang (Arm Technology China) 2019-10-11 5:43 ` james qian wang (Arm Technology China) 2019-10-14 8:56 ` Daniel Vetter 2019-10-14 8:56 ` Daniel Vetter 2019-10-14 9:58 ` james qian wang (Arm Technology China) 2019-10-14 9:58 ` james qian wang (Arm Technology China) 2019-10-14 15:33 ` Daniel Vetter 2019-10-14 15:33 ` Daniel Vetter 2019-10-14 15:58 ` Ilia Mirkin 2019-10-14 15:58 ` Ilia Mirkin 2019-10-15 1:16 ` james qian wang (Arm Technology China) 2019-10-15 1:16 ` james qian wang (Arm Technology China) 2019-10-15 3:48 ` Ilia Mirkin 2019-10-15 3:48 ` Ilia Mirkin 2019-10-15 8:04 ` james qian wang (Arm Technology China) [this message] 2019-10-15 8:04 ` james qian wang (Arm Technology China) 2019-10-15 8:21 ` Mihail Atanassov 2019-10-15 8:21 ` Mihail Atanassov 2019-10-15 8:59 ` james qian wang (Arm Technology China) 2019-10-15 8:59 ` james qian wang (Arm Technology China) 2019-10-11 5:43 ` [PATCH v2 2/4] drm/komeda: Add drm_lut_to_fgamma_coeffs() james qian wang (Arm Technology China) 2019-10-11 5:43 ` james qian wang (Arm Technology China) 2019-10-11 5:43 ` [PATCH v2 3/4] drm/komeda: Add drm_ctm_to_coeffs() james qian wang (Arm Technology China) 2019-10-11 5:43 ` james qian wang (Arm Technology China) 2019-10-11 5:43 ` [PATCH v2 4/4] drm/komeda: Adds gamma and color-transform support for DOU-IPS james qian wang (Arm Technology China) 2019-10-11 5:43 ` james qian wang (Arm Technology China) 2019-10-11 6:21 ` sandy.huang 2019-10-11 6:21 ` sandy.huang 2019-10-11 7:12 ` james qian wang (Arm Technology China)
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