Re: [PATCH] drm/color: un-inline drm_color_lut_extract()

[Jani Nikula <jani.nikula@intel.com>]

On Mon, 23 Jan 2017, Daniel Vetter <daniel@ffwll.ch> wrote:
> On Mon, Jan 23, 2017 at 11:42:59AM +0200, Jani Nikula wrote:
>> The function is not that big, but it's also not used for anything
>> performance critical. Make it a normal function.
>> 
>> As a side effect, this apparently makes sparse smarter about what it's
>> doing, and gets rid of the warning:
>> 
>> ./include/drm/drm_color_mgmt.h:53:28: warning: shift too big (4294967295) for type unsigned long
>> ./include/drm/drm_color_mgmt.h:53:28: warning: cast truncates bits from constant value (8000000000000000 becomes 0)
>
> Not really clear to me what's going on, but if it helps ...

Apparently sparse is clever enough to notice bit_precision < 16 when
this is a regular function, but not when it's an inline function. The
second warning we could get rid of just by changing s/1UL/1U/.

BR,
Jani.

>
>> Cc: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
>> Signed-off-by: Jani Nikula <jani.nikula@intel.com>
>
> Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
>
>> ---
>>  drivers/gpu/drm/drm_color_mgmt.c | 24 ++++++++++++++++++++++++
>>  include/drm/drm_color_mgmt.h     | 27 ++-------------------------
>>  2 files changed, 26 insertions(+), 25 deletions(-)
>> 
>> diff --git a/drivers/gpu/drm/drm_color_mgmt.c b/drivers/gpu/drm/drm_color_mgmt.c
>> index 789b4c65cd69..5618f60c7690 100644
>> --- a/drivers/gpu/drm/drm_color_mgmt.c
>> +++ b/drivers/gpu/drm/drm_color_mgmt.c
>> @@ -88,6 +88,30 @@
>>   */
>>  
>>  /**
>> + * drm_color_lut_extract - clamp&round LUT entries
>> + * @user_input: input value
>> + * @bit_precision: number of bits the hw LUT supports
>> + *
>> + * 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.
>> + */
>> +uint32_t drm_color_lut_extract(uint32_t user_input, uint32_t bit_precision)
>> +{
>> +	uint32_t val = user_input;
>> +	uint32_t max = 0xffff >> (16 - bit_precision);
>> +
>> +	/* Round only if we're not using full precision. */
>> +	if (bit_precision < 16) {
>> +		val += 1UL << (16 - bit_precision - 1);
>> +		val >>= 16 - bit_precision;
>> +	}
>> +
>> +	return clamp_val(val, 0, max);
>> +}
>> +EXPORT_SYMBOL(drm_color_lut_extract);
>> +
>> +/**
>>   * drm_crtc_enable_color_mgmt - enable color management properties
>>   * @crtc: DRM CRTC
>>   * @degamma_lut_size: the size of the degamma lut (before CSC)
>> diff --git a/include/drm/drm_color_mgmt.h b/include/drm/drm_color_mgmt.h
>> index c767238ac9d5..bce4a532836d 100644
>> --- a/include/drm/drm_color_mgmt.h
>> +++ b/include/drm/drm_color_mgmt.h
>> @@ -25,6 +25,8 @@
>>  
>>  #include <linux/ctype.h>
>>  
>> +uint32_t drm_color_lut_extract(uint32_t user_input, uint32_t bit_precision);
>> +
>>  void drm_crtc_enable_color_mgmt(struct drm_crtc *crtc,
>>  				uint degamma_lut_size,
>>  				bool has_ctm,
>> @@ -33,29 +35,4 @@ void drm_crtc_enable_color_mgmt(struct drm_crtc *crtc,
>>  int drm_mode_crtc_set_gamma_size(struct drm_crtc *crtc,
>>  				 int gamma_size);
>>  
>> -/**
>> - * drm_color_lut_extract - clamp&round LUT entries
>> - * @user_input: input value
>> - * @bit_precision: number of bits the hw LUT supports
>> - *
>> - * 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.
>> - */
>> -static inline uint32_t drm_color_lut_extract(uint32_t user_input,
>> -					     uint32_t bit_precision)
>> -{
>> -	uint32_t val = user_input;
>> -	uint32_t max = 0xffff >> (16 - bit_precision);
>> -
>> -	/* Round only if we're not using full precision. */
>> -	if (bit_precision < 16) {
>> -		val += 1UL << (16 - bit_precision - 1);
>> -		val >>= 16 - bit_precision;
>> -	}
>> -
>> -	return clamp_val(val, 0, max);
>> -}
>> -
>> -
>>  #endif
>> -- 
>> 2.1.4
>> 
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-- 
Jani Nikula, Intel Open Source Technology Center
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