STRUCT MALI_C55_AE_1024BIN_HIST(9)

💖 NAME

okay so bestie, this is the manual page for struct mali_c55_ae_1024bin_hist — the Auto Exposure 1024-bin histogram statistics struct. and yes we're doing this in the Kernel API Manual, welcome to the group chat 🫶

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✨ SYNOPSIS

here's the whole entire struct, no notes, she's small but she's doing a lot:

struct mali_c55_ae_1024bin_hist {
    __u16 bins[1024];
 };

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🌸 MEMBERS

• bins — a 1024 element array of 16-bit pixel counts. that's it. that's the member. 1024 of them. lowkey iconic 💅

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🦋 DESCRIPTION

so the 1024-bin histogram module? she collects image-global but zone-weighted intensity distributions of pixels into fixed-width bins. very demure, very mindful. 🎀

the modules can be configured into different "plane modes", and those affect what actually ends up in the collected statistics:

• plane mode 0 — pixel intensities are taken regardless of colour plane, all crammed into a single 1024-bin histogram with a bin width of 4. one big happy histogram ✨
• plane mode 1 — four 256-bin histograms with a bin width of 16 are collected, one for each CFA colour plane. four little guys, each doing their own thing 🌈
• plane modes 4, 5, 6 and 7 — two 512-bin histograms with a bin width of 8 are collected. in each mode, one of the colour planes goes into the first histogram and all the others get combined into the second. duo energy, fr fr 🫶

the histograms are stored consecutively in the bins array. no gaps, no drama.

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🔥 the exponent/mantissa situation (iykyk)

the 16-bit pixel counts are stored as a 4-bit exponent in the most significant bits followed by a 12-bit mantissa. not me having to read this twice 😭

conversion to a usable format can be done according to the following pseudo-code:

if (e == 0) {
        bin = m * 2;
} else {
        bin = (m + 4096) * 2^e
}

where:

• e is the exponent value in range 0..15
• m is the mantissa value in range 0..4095

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🧚 the three masking methods

the pixels used in calculating the statistics can be masked using three methods, and yes there are exactly three, bestie, don't come for me:

1. Pixels can be skipped in X and Y directions independently.
2. Minimum/Maximum intensities can be configured
3. Zones can be differentially weighted, including 0 weighted to mask them

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⭐ where does the data even come from

the data for this histogram can be collected from different tap points in the ISP depending on configuration:

• after the white balance or digital gain blocks
• or immediately after the input crossbar

that's the whole vibe check on tap points 💀

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🎀 SEE ALSO

Kernel file ./include/uapi/linux/media/arm/mali-c55-config.h and honestly the whole friend group:

• struct mali_c55_ae_5bin_hist(9)
• struct mali_c55_awb_average_ratios(9)
• struct mali_c55_af_statistics(9)
• struct mali_c55_stats_buffer(9)
• enum mali_c55_param_block_type(9)
• struct mali_c55_params_sensor_off_preshading(9)
• enum mali_c55_aexp_hist_tap_points(9)
• enum mali_c55_aexp_skip_x(9)
• enum mali_c55_aexp_skip_y(9)
• enum mali_c55_aexp_row_column_offset(9)
• enum mali_c55_aexp_hist_plane_mode(9)
• struct mali_c55_params_aexp_hist(9)
• struct mali_c55_params_aexp_weights(9)
• struct mali_c55_params_digital_gain(9)
• enum mali_c55_awb_stats_mode(9)
• struct mali_c55_params_awb_gains(9)
• enum mali_c55_params_awb_tap_points(9)
• struct mali_c55_params_awb_config(9)
• struct mali_c55_params_mesh_shading_config(9)
• struct mali_c55_params_mesh_shading_selection(9)
• struct mali_c55_params_ccm(9)
• struct mali_c55_params_gamma(9)
• MALI_C55_PARAMS_MAX_SIZE(9)

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and that's the page!! 💜 this little number lives at ./include/uapi/linux/media/arm, stamped October 2026, and she ate. periodt. 💅✨