linux/drivers/staging/media/atomisp/pci/sh_css_param_shading.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Support for Intel Camera Imaging ISP subsystem.
 * Copyright (c) 2015, Intel Corporation.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms and conditions of the GNU General Public License,
 * version 2, as published by the Free Software Foundation.
 *
 * This program is distributed in the hope it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 * more details.
 */

#include <linux/math.h>
#include <linux/slab.h>

#include <math_support.h>
#include "sh_css_param_shading.h"
#include "ia_css_shading.h"
#include "assert_support.h"
#include "sh_css_defs.h"
#include "sh_css_internal.h"
#include "ia_css_debug.h"
#include "ia_css_pipe_binarydesc.h"

#include "sh_css_hrt.h"

#include "platform_support.h"

/* Bilinear interpolation on shading tables:
 * For each target point T, we calculate the 4 surrounding source points:
 * ul (upper left), ur (upper right), ll (lower left) and lr (lower right).
 * We then calculate the distances from the T to the source points: x0, x1,
 * y0 and y1.
 * We then calculate the value of T:
 *   dx0*dy0*Slr + dx0*dy1*Sur + dx1*dy0*Sll + dx1*dy1*Sul.
 * We choose a grid size of 1x1 which means:
 *   dx1 = 1-dx0
 *   dy1 = 1-dy0
 *
 *   Sul dx0         dx1      Sur
 *    .<----->|<------------->.
 *    ^
 * dy0|
 *    v        T
 *    -        .
 *    ^
 *    |
 * dy1|
 *    v
 *    .                        .
 *   Sll                      Slr
 *
 * Padding:
 * The area that the ISP operates on can include padding both on the left
 * and the right. We need to padd the shading table such that the shading
 * values end up on the correct pixel values. This means we must padd the
 * shading table to match the ISP padding.
 * We can have 5 cases:
 * 1. All 4 points fall in the left padding.
 * 2. The left 2 points fall in the left padding.
 * 3. All 4 points fall in the cropped (target) region.
 * 4. The right 2 points fall in the right padding.
 * 5. All 4 points fall in the right padding.
 * Cases 1 and 5 are easy to handle: we simply use the
 * value 1 in the shading table.
 * Cases 2 and 4 require interpolation that takes into
 * account how far into the padding area the pixels
 * fall. We extrapolate the shading table into the
 * padded area and then interpolate.
 */
static void
crop_and_interpolate(unsigned int cropped_width,
		     unsigned int cropped_height,
		     unsigned int left_padding,
		     int right_padding,
		     int top_padding,
		     const struct ia_css_shading_table *in_table,
		     struct ia_css_shading_table *out_table,
		     enum ia_css_sc_color color)
{ … }

void
sh_css_params_shading_id_table_generate(
    struct ia_css_shading_table **target_table,
    unsigned int table_width,
    unsigned int table_height)
{ … }

void
prepare_shading_table(const struct ia_css_shading_table *in_table,
		      unsigned int sensor_binning,
		      struct ia_css_shading_table **target_table,
		      const struct ia_css_binary *binary,
		      unsigned int bds_factor)
{ … }

struct ia_css_shading_table *
ia_css_shading_table_alloc(
    unsigned int width,
    unsigned int height)
{ … }

void
ia_css_shading_table_free(struct ia_css_shading_table *table)
{ … }