On Monday, 14 October 2019 10:43:39 BST james qian wang (Arm Technology China) wrote:
On Fri, Oct 11, 2019 at 08:26:53AM +0000, Mihail Atanassov wrote:
Hi James,
On Friday, 11 October 2019 06:45:27 BST 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.wang@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, the m must <= 31
- @n: number of fractinal bits the n must <= 32
@m: number of integer bits, only support m <= 31 @n: number of fractinal bitsm only support n <= 32
Hehe, guess what I didn't do? Also, [nit], s/fractinal/fractional/.
- 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);
This doesn't account for n > 32, which is perfectly possible (e.g. Q1.63).
- 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);
This also doesn't account for n + m == 64.
Yes the func is only for support m <= 31, n <= 32
But I'm not sure, how to handle the unsupport case ? Maybe just mention it in Doc is enough.
I'd personally appreciate a WARN_ON(...)*. My comment was motivated by the unchecked nature of the limitation, which might surprise a dev who didn't read the doc before using the function (like myself :)).
Actually, the limitations are more than specified, BIT(n + m) is only valid for (n + m < 32) on LP32 systems.
At least change those to BIT_ULL(), then:
Reviewed-by: Mihail Atanassov mihail.atanassov@arm.com
* - gcc9.2 doesn't give me any compile-time warnings for using this func incorrectly.
- 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