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+# libcamera (Surface Pro 12" Gen 1)
+
+Fedora's `libcamera`, rebuilt with the patches this board needs.
+
+Used by [Fedora KIWI descriptions, modified by me for Surface Pro 12"](https://sayag.it/fedora-linux-surface-pro-12in/kiwi-descriptions).
+
+## Why a rebuild
+
+libcamera compiles its per-sensor knowledge into `libcamera.so`. A
+`CameraSensorHelper` carries the analogue gain model and the black level, and
+there is no plugin mechanism for either, so a sensor libcamera does not know
+gets no usable AGC from the software ISP.
+
+The Surface Pro 12"'s front camera is an `ov02c10`, which upstream libcamera has
+never heard of:
+
+```
+WARN IPASoft soft_simple.cpp:104 IPASoft: Failed to create camera sensor helper for ov02c10
+INFO IPASoft soft_simple.cpp:257 IPASoft: Exposure 4-2320, gain 16-248 (1)
+```
+
+Those numbers are the raw gain register, not a gain: AGC believes the sensor
+cannot go below 16x, balances exposure against a fiction, and leaves the preview
+dark under a green-grey veil, because it also has no black level to subtract.
+With the helper in place the same sensor reports what it really is:
+
+```
+INFO IPASoft soft_simple.cpp:258 IPASoft: Exposure 4-3206, gain 1-15.5 (0.145)
+```
+
+which matches the kernel driver, where `OV02C10_REG_ANALOG_GAIN` runs from
+`0x10` to `0xf8` with four fractional bits.
+
+## What gets applied
+
+| Patch | Fixes |
+| --- | --- |
+| `patches/0001-libipa-camera_sensor-add-ov02c10.patch` | Adds the `ov02c10` `CameraSensorHelper` (gain `code/16`, black level `0x40` at 10 bits) and its `camera_sensor_properties` entry. |
+
+## Versioning
+
+The rebuild takes Fedora's release and appends a suffix, so
+`0.7.2-4.fc45` becomes `0.7.2-4.sp12in1.fc45`. That sorts above the build it
+came from, which is what makes the repository's `priority="1"` produce the
+patched package.
+
+## Building
+
+Must run on aarch64, and needs the source repositories reachable
+(`dnf download --source` comes from `dnf5-plugins`).
+
+```bash
+# Resolve only: print the RPMs the build would produce, and exit
+./build.sh -n
+
+# Build them into ./RPMS
+./build.sh
+
+# Override the release suffix (the pipeline sets it from the tag)
+RELEASE_SUFFIX=sp12in2 ./build.sh
+```
+
+`build.sh` downloads Fedora's source RPM, copies `patches/*.patch` into it,
+appends a `PatchNN:` line for each after the last one Fedora ships (the spec
+uses `%autosetup -p1`, so nothing has to call `%patch`), rewrites `Release:`,
+then runs `dnf builddep` and `rpmbuild -bb`. The scratch tree is reused between
+runs, so `-n` followed by a real build does not download twice.
+
+## Publishing
+
+Tagging `fedora-<fedora_ver>-libcamera-<release_suffix>`, e.g.
+`fedora-45-libcamera-sp12in1`, runs the pipeline: the tag picks the build
+container and supplies `RELEASE_SUFFIX`, and the resulting packages go to the
+same repository as the kernel, served at
+
+    https://rpm.sayag.it/kernel-sp12in/fedora/45/aarch64/