[DEV][PATCH] KCAL - Advanced color control for Qualcomm MDSS 8x10/8x26/8974/8084/8939

Hello! If you're keen on custom kernels, especially for Nexus devices, you've probably heard the term Color/Gamma Control thrown around a bit. A once *very* device dependent feature now made available for the following chipsets:

Quote:

8x10
8974 v1.0
8x26 v1.0
8x26 v2.0, 8926 v1.0
8926 v2.0
8974 v2.0
8974 v3.0 (Pro)
8084 v1.0
8084 v1.1
8994 v1.0
8916 v1.0
8939 v1.0
8092 v1.0

Color calibration allows you to use an app (or root shell) to manipulate the following post-processing features of the Qualcomm MDSS:

Quote:

RGB Multipliers (Polynomial Color Correction)
Display Color Inversion (Inverse Gamma Correction)
Hue/Saturation/Value/Contrast Manipulation (Picture Adjustment)

Too confusing? Here's a video demonstration by @Andromjb:


Sysfs paths/variables:

Quote:

/sys/devices/platform/kcal_ctrl.0/kcal - (0-256 0-256 0-256) - Controls R/G/B Multipliers
/sys/devices/platform/kcal_ctrl.0/kcal_min - (0-256) - Controls minimum RGB Multiplier value
/sys/devices/platform/kcal_ctrl.0/kcal_enable - (0-1) - Enables/Disables RGB Multiplier Control
/sys/devices/platform/kcal_ctrl.0/kcal_invert - (0-1) - Enables/Disables Display Inversion Mode
/sys/devices/platform/kcal_ctrl.0/kcal_sat - (224-383 or 128) - Controls saturation intensity - use 128 for grayscale mode
/sys/devices/platform/kcal_ctrl.0/kcal_hue - (0-1536) - Controls display hue - may have issues with msm8x26 in the higher values
/sys/devices/platform/kcal_ctrl.0/kcal_val - (128-383) - Controls display value
/sys/devices/platform/kcal_ctrl.0/kcal_cont - (128-383) - Controls display contrast

Link your favorite kernel developer back to this thread and ask them to add support!

KCAL for MDP5
https://github.com/savoca/kernel-msm/commits/mdp5

KCAL for MDP3 (Only supports RGB multipliers):
https://github.com/savoca/kernel-msm/commits/mdp3

And finally, an app to control your display - available for free here:
http://downloads.codefi.re/savoca/kcal

Thank you to LG for the display inversion control and code reference, also thank you to @faux123 for insight/reference with MDP3 RGB multipliers and @eng.stk for testing on APQ8084