On Mon, Oct 14, 2019 at 09:58:20AM +0000, james qian wang (Arm Technology China) wrote: > On Mon, Oct 14, 2019 at 10:56:05AM +0200, Daniel Vetter wrote: > > On Fri, Oct 11, 2019 at 05:43:09AM +0000, james qian wang (Arm Technology > > China) wrote: > > > Add a new helper function drm_color_ctm_s31_32_to_qm_n() for driver to > > > convert S31.32 sign-magnitude to Qm.n 2's complement that supported by > > > hardware. > > > > > > Signed-off-by: james qian wang (Arm Technology China) > > > <james.qian.w...@arm.com> > > > --- > > > drivers/gpu/drm/drm_color_mgmt.c | 23 +++++++++++++++++++++++ > > > include/drm/drm_color_mgmt.h | 2 ++ > > > 2 files changed, 25 insertions(+) > > > > > > diff --git a/drivers/gpu/drm/drm_color_mgmt.c > > > b/drivers/gpu/drm/drm_color_mgmt.c > > > index 4ce5c6d8de99..3d533d0b45af 100644 > > > --- a/drivers/gpu/drm/drm_color_mgmt.c > > > +++ b/drivers/gpu/drm/drm_color_mgmt.c > > > @@ -132,6 +132,29 @@ uint32_t drm_color_lut_extract(uint32_t user_input, > > > uint32_t bit_precision) > > > } > > > EXPORT_SYMBOL(drm_color_lut_extract); > > > > > > +/** > > > + * drm_color_ctm_s31_32_to_qm_n > > > + * > > > + * @user_input: input value > > > + * @m: number of integer bits > > > + * @n: number of fractinal bits > > > + * > > > + * Convert and clamp S31.32 sign-magnitude to Qm.n 2's complement. > > > > What's the Q meaning here? Also maybe specify that the higher bits above > > m+n are cleared to all 0 or all 1. Unit test would be lovely too. Anyway: > > The Q used to represent signed two's complement. > > For detail: https://en.wikipedia.org/wiki/Q_(number_format) > > And it Q is 2's complement, so the value of higher bit equal to > sign-bit. > All 1 if it is negative > 0 if it is positive.
Ah I didn't know about this notation, I think in other drm docs we just used m.n 2's complement to denote this layout. Up to you I think. -Daniel > > James > > > Reviewed-by: Daniel Vetter <daniel.vet...@ffwll.ch> > > > > > + */ > > > +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] */ > > > + val = clamp_val(mag, 0, negative ? BIT(n + m) : BIT(n + m) - 1); > > > + > > > + return negative ? 0ll - val : val; > > > +} > > > +EXPORT_SYMBOL(drm_color_ctm_s31_32_to_qm_n); > > > + > > > /** > > > * drm_crtc_enable_color_mgmt - enable color management properties > > > * @crtc: DRM CRTC > > > diff --git a/include/drm/drm_color_mgmt.h b/include/drm/drm_color_mgmt.h > > > index d1c662d92ab7..60fea5501886 100644 > > > --- a/include/drm/drm_color_mgmt.h > > > +++ b/include/drm/drm_color_mgmt.h > > > @@ -30,6 +30,8 @@ struct drm_crtc; > > > struct drm_plane; > > > > > > uint32_t drm_color_lut_extract(uint32_t user_input, uint32_t > > > bit_precision); > > > +uint64_t drm_color_ctm_s31_32_to_qm_n(uint64_t user_input, > > > + uint32_t m, uint32_t n); > > > > > > void drm_crtc_enable_color_mgmt(struct drm_crtc *crtc, > > > uint degamma_lut_size, > > > -- > > > 2.20.1 > > > > > > _______________________________________________ > > > dri-devel mailing list > > > dri-devel@lists.freedesktop.org > > > https://lists.freedesktop.org/mailman/listinfo/dri-devel > > > > -- > > Daniel Vetter > > Software Engineer, Intel Corporation > > http://blog.ffwll.ch > IMPORTANT NOTICE: The contents of this email and any attachments are > confidential and may also be privileged. If you are not the intended > recipient, please notify the sender immediately and do not disclose the > contents to any other person, use it for any purpose, or store or copy the > information in any medium. Thank you. > _______________________________________________ > dri-devel mailing list > dri-devel@lists.freedesktop.org > https://lists.freedesktop.org/mailman/listinfo/dri-devel -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch