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/device/soc/rockchip/common/sdk_linux/drivers/video/backlight/
H A Dpwm_bl.c157 * CIE lightness to PWM conversion.
159 * The CIE 1931 lightness formula is what actually describes how we perceive
165 * is a number between 0.0 and 1.0; and L* is the lightness, how bright a human
171 static u64 cie1931(unsigned int lightness) in cie1931() argument
176 * @lightness is given as a number between 0 and 1, expressed in cie1931()
182 lightness *= 0x64; in cie1931()
183 if (lightness <= (0x8 * PWM_LUMINANCE_SCALE)) { in cie1931()
184 retval = DIV_ROUND_CLOSEST(lightness * 0xa, 0x2349); in cie1931()
186 retval = (lightness + (0x10 * PWM_LUMINANCE_SCALE)) / 0x74; in cie1931()

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