Re: [PATCH v13 4/9] media: uapi: Add CAMSS ISP configuration definition

[Jacopo Mondi <jacopo.mondi@ideasonboard.com>]

Hi Loic

On Tue, Nov 03, 2026 at 09:05:48PM +0100, Loic Poulain wrote:
> Add the uapi header qcom-camss-config.h defining the ISP parameter
> structures used by the CAMSS Offline Processing Engine (OPE) driver.
> This includes structures for white balance, chroma enhancement and
> color correction configuration.
>
> The block type enum is shared across CAMSS ISPs so that userspace only
> has to deal with a single set of block identifiers.
>
> Reviewed-by: Hans de Goede <johannes.goede@oss.qualcomm.com>
> Tested-by: Hans de Goede <johannes.goede@oss.qualcomm.com>
> Signed-off-by: Loic Poulain <loic.poulain@oss.qualcomm.com>
> ---
>  include/uapi/linux/qcom-camss-config.h | 217 +++++++++++++++++++++++++++++++++
>  1 file changed, 217 insertions(+)
>
> diff --git a/include/uapi/linux/qcom-camss-config.h b/include/uapi/linux/qcom-camss-config.h
> new file mode 100644
> index 0000000000000000000000000000000000000000..543c1682f8aed3b07d7085f54a24eb632ea190a8
> --- /dev/null
> +++ b/include/uapi/linux/qcom-camss-config.h

We have (kind of) recently introduced include/uapi/linux/media

This file should probably be:
include/uapi/linux/media/qcom/camss-config.h

> @@ -0,0 +1,217 @@
> +/* SPDX-License-Identifier: GPL-2.0-only WITH Linux-syscall-note */
> +/*
> + * Qualcomm CAMSS ISP Driver - Userspace API
> + *
> + * Copyright (c) Qualcomm Technologies, Inc. and/or its subsidiaries.
> + */
> +
> +#ifndef _UAPI_LINUX_QCOM_CAMSS_CONFIG_H
> +#define _UAPI_LINUX_QCOM_CAMSS_CONFIG_H
> +
> +#include <linux/types.h>
> +#include <linux/media/v4l2-isp.h>
> +
> +/**
> + * enum camss_params_block_type - CAMSS ISP parameter block identifiers
> + *
> + * Each value identifies one ISP processing block.  The value is placed in
> + * the @type field of &struct v4l2_isp_block_header.
> + *
> + * @CAMSS_PARAMS_WB_GAIN: white balance gains and offsets (CLC_WB),
> + *	&struct camss_params_wb_gain
> + * @CAMSS_PARAMS_CHROMA_ENHAN: RGB to YUV colour transfer matrix
> + *	(CLC_CHROMA_ENHAN), &struct camss_params_chroma_enhan
> + * @CAMSS_PARAMS_COLOR_CORRECT: colour correction matrix (CLC_CC),
> + *	&struct camss_params_color_correct
> + * @CAMSS_PARAMS_GAMMA: per-channel gamma correction curves (CLC_GLUT),
> + *	&struct camss_params_gamma
> + */
> +enum camss_params_block_type {
> +	CAMSS_PARAMS_WB_GAIN = 1,
> +	CAMSS_PARAMS_CHROMA_ENHAN = 2,
> +	CAMSS_PARAMS_COLOR_CORRECT = 3,
> +	CAMSS_PARAMS_GAMMA = 4,
> +};
> +
> +/* Number of entries in each gamma channel LUT. */
> +#define CAMSS_GAMMA_LUT_SIZE	256
> +
> +/**
> + * struct camss_params_wb_gain - White Balance gains
> + *
> + * Implements the CLC_WB pipeline module.  The pipeline applies three
> + * sequential operations per channel::
> + *
> + *   1. Subtract sub-offset (black-level subtraction)
> + *   2. Multiply by gain    (colour balance)
> + *   3. Add add-offset      (output pedestal)
> + *
> + * Gains are 15uQ10 (15-bit unsigned, 10 fractional bits). Offsets
> + * are 16-bit unsigned, normalised to full input scale (65535 = 1.0)
> + *
> + * @header:   block header; @header.type = CAMSS_PARAMS_WB_GAIN
> + * @g_gain:   green channel gain (15uQ10, 1024 = 1.0)
> + * @b_gain:   blue  channel gain (15uQ10, 1024 = 1.0)
> + * @r_gain:   red   channel gain (15uQ10, 1024 = 1.0)
> + * @g_sub:    green sub-offset, subtracted before gain (16u)
> + * @b_sub:    blue  sub-offset, subtracted before gain (16u)
> + * @r_sub:    red   sub-offset, subtracted before gain (16u)
> + * @g_add:    green add-offset, added after gain (16u)
> + * @b_add:    blue  add-offset, added after gain (16u)
> + * @r_add:    red   add-offset, added after gain (16u)
> + * @_pad:     padding for 64-bit alignment, must be zero
> + */
> +struct camss_params_wb_gain {
> +	struct v4l2_isp_block_header header;
> +	__u16 g_gain;
> +	__u16 b_gain;
> +	__u16 r_gain;
> +	__u16 g_sub;
> +	__u16 b_sub;
> +	__u16 r_sub;
> +	__u16 g_add;
> +	__u16 b_add;
> +	__u16 r_add;
> +	__u16 _pad[3];
> +} __attribute__((aligned(8)));
> +
> +/**
> + * struct camss_params_chroma_enhan - RGB to YUV colour transfer matrix
> + *
> + * Implements the CLC_CHROMA_ENHAN pipeline module. All coefficients are
> + * signed 12-bit fixed-point Q3.8 (range roughly -8.0 to +7.996).
> + *
> + * RGB2Y - Luma (Y) coefficients::
> + *
> + *   Y = v0 * R + v1 * G + v2 * B
> + *
> + * RGB2Cb - Chroma (Cb) coefficients::
> + *
> + *   Cb = a x ((B - G) + b(R - G)) + KCb
> + *   with:
> + *     a = ap, when (B-G) + b(R-G) > 0; a = am, when (B-G) + b(R-G) ≤ 0;
> + *     b = bp when (R-G) > 0; b = bm when (R-G) ≤ 0
> + *
> + * RGB2Cr - Chroma (Cr) coefficients::
> + *
> + *   Cr = c x ((R - G) + d(B - G)) + KCr
> + *   with:
> + *     c = cp, when (R-G) + d(B-G) > 0; c = cm, when (R-G) + d(B-G) ≤ 0
> + *     d = dp when (B-G) > 0; d = dm when (B-G) ≤ 0
> + *
> + * @header:   generic block header; @header.type = CAMSS_PARAMS_CHROMA_ENHAN
> + * @luma_v0:  R-to-Y coefficient (12sQ8)
> + * @luma_v1:  G-to-Y coefficient (12sQ8)
> + * @luma_v2:  B-to-Y coefficient (12sQ8)
> + * @luma_k:   Y output offset    (9s,  0 = no offset)
> + * @coeff_ap: Cb positive coefficient (12sQ8)
> + * @coeff_am: Cb negative coefficient (12sQ8)
> + * @coeff_bp: Cb positive coefficient (12sQ8)
> + * @coeff_bm: Cb negative coefficient (12sQ8)
> + * @coeff_cp: Cr positive coefficient (12sQ8)
> + * @coeff_cm: Cr negative coefficient (12sQ8)
> + * @coeff_dp: Cr positive coefficient (12sQ8)
> + * @coeff_dm: Cr negative coefficient (12sQ8)
> + * @kcb:      Cb output offset        (11s)
> + * @kcr:      Cr output offset        (11s)
> + * @_pad:     padding for 64-bit alignment, must be zero
> + */
> +struct camss_params_chroma_enhan {
> +	struct v4l2_isp_block_header header;
> +	__s16 luma_v0;
> +	__s16 luma_v1;
> +	__s16 luma_v2;
> +	__s16 luma_k;
> +	__s16 coeff_ap;
> +	__s16 coeff_am;
> +	__s16 coeff_bp;
> +	__s16 coeff_bm;
> +	__s16 coeff_cp;
> +	__s16 coeff_cm;
> +	__s16 coeff_dp;
> +	__s16 coeff_dm;
> +	__s16 kcb;
> +	__s16 kcr;
> +	__u16 _pad[2];
> +} __attribute__((aligned(8)));
> +
> +/**
> + * struct camss_params_color_correct - colour correction matrix
> + *
> + * Implements the CLC_CC pipeline module.  The matrix computes::
> + *
> + *   Out_ch0 (G) = a0*G + b0*B + c0*R + k0
> + *   Out_ch1 (B) = a1*G + b1*B + c1*R + k1
> + *   Out_ch2 (R) = a2*G + b2*B + c2*R + k2
> + *
> + * The @qfactor member selects the fixed-point format of all coefficients::
> + *
> + *   0 = 12sQ7  (range ~-16.0 .. +15.992)
> + *   1 = 12sQ8  (range  ~-8.0 ..  +7.996)
> + *   2 = 12sQ9  (range  ~-4.0 ..  +3.998)
> + *   3 = 12sQ10 (range  ~-2.0 ..  +1.999)
> + *
> + * @header:  block header; @header.type = CAMSS_PARAMS_COLOR_CORRECT
> + * @a:       G-input coefficients per output channel (12s;
> + *           a[0]=Out_G, a[1]=Out_B, a[2]=Out_R)
> + * @b:       B-input coefficients (12s)
> + * @c:       R-input coefficients (12s)
> + * @k:       per-output-channel offsets (typically 9s effective)
> + * @qfactor: Q-format selector (2u), see above
> + * @_pad:    padding for 64-bit alignment, must be zero
> + */
> +struct camss_params_color_correct {
> +	struct v4l2_isp_block_header header;
> +	__s16 a[3];
> +	__s16 b[3];
> +	__s16 c[3];
> +	__s16 k[3];
> +	__u16 qfactor;
> +	__u16 _pad[3];
> +} __attribute__((aligned(8)));
> +
> +/**
> + * struct camss_params_gamma - per-channel gamma correction curves
> + *
> + * Implements the CLC_GLUT pipeline module, applied in the RGB domain.  It
> + * holds one independent lookup table per colour channel. Each table is a
> + * direct (not segmented) map of input level to output level.
> + *
> + * Each table has @CAMSS_GAMMA_LUT_SIZE (256) entries of 16-bit unsigned
> + * output. The number of significant output bits follows the width of the
> + * engine's internal bus; the upper bits are ignored by the hardware.
> + *
> + * The module maps a 12-bit input to an 8-bit output: the top 8 input bits
> + * index the table and the low 4 bits are used to linearly interpolate
> + * between adjacent entries. Entry i therefore represents the output for
> + * input level i/255 of full scale.
> + * Output range: 0x00 = black, 0xFF = white.
> + *
> + * How to fill a curve (same on all three channels for pure luminance
> + * gamma; different curves per channel additionally shift colour balance)::
> + *
> + *   Identity (pass-through, gamma 1.0):
> + *     lut[i] = i;                                // i = 0..255
> + *
> + *   Encode with gamma g (e.g. sRGB-like, g = 2.2):
> + *     lut[i] = round(pow(i / 255.0, 1.0 / g) * 255.0);
> + *
> + * @header:  block header; @header.type = CAMSS_PARAMS_GAMMA
> + * @glut:    green channel gamma curve
> + * @blut:    blue  channel gamma curve
> + * @rlut:    red   channel gamma curve
> + */
> +struct camss_params_gamma {
> +	struct v4l2_isp_block_header header;
> +	__u16 glut[CAMSS_GAMMA_LUT_SIZE];
> +	__u16 blut[CAMSS_GAMMA_LUT_SIZE];
> +	__u16 rlut[CAMSS_GAMMA_LUT_SIZE];
> +} __attribute__((aligned(8)));
> +
> +#define CAMSS_PARAMS_OPE_MAX_PAYLOAD		\
> +	(sizeof(struct camss_params_wb_gain)	+\
> +	 sizeof(struct camss_params_chroma_enhan)	+\
> +	 sizeof(struct camss_params_color_correct)	+\
> +	 sizeof(struct camss_params_gamma))
> +
> +#endif /* _UAPI_LINUX_QCOM_CAMSS_CONFIG_H */
>
> --
> 2.34.1
>
>