Initial commit: CB-C6s-STU GSI Fixes

TWRP flashable zip for CB-C6s-STU tablet running GSI.
- build.prop: append tablet characteristics, brightness, orientation, BT offload
- goodix_ts.idc: touchscreen IDC config
- sensor_config.xml: camera sensor module mapping (hi846 / gc8034)
- Shell-script update-binary with append-only build.prop logic

README.md

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+# CB-C6s-STU GSI Fixes
+
+TWRP flashable zip that applies device-specific fixes for the **CB-C6s-STU**
+tablet when running a Generic System Image (GSI). All `build.prop` changes
+are **appended** — the existing file is never replaced.
+
+## What it fixes
+
+| Area | File | Problem | Fix |
+|------|------|---------|-----|
+| System properties | `build.prop` | Missing tablet characteristics, wrong brightness range, portrait-only orientation, broken Bluetooth A2DP offload | Append missing properties |
+| Touchscreen | `goodix_ts.idc` | Touch orientation and input device type not declared | Install IDC config for Goodix touch panel |
+| Camera sensors | `sensor_config.xml` | Rear/front camera sensor modules not configured | Install sensor config for hi846 / gc8034 modules |
+
+## Files
+
+```
+CB-C6s-STU-GSI-Fixes.zip
+├── META-INF/com/google/android/
+│   ├── update-binary        # Shell script — all install logic
+│   └── updater-script       # Placeholder (TWRP uses shell-script mode)
+├── system/
+│   ├── build.prop           # Properties appended to /system/build.prop
+│   └── usr/idc/
+│       └── goodix_ts.idc    # Touchscreen input device config
+└── vendor/etc/
+    └── sensor_config.xml    # Camera sensor module mapping
+```
+
+### build.prop entries
+
+Appended to the device's existing `/system/build.prop`:
+
+```ini
+# Tablet characteristics
+ro.build.characteristics=tablet
+
+# Workaround: Set max brightness of sprd_backlight to 1023
+persist.sys.qcom-brightness=1023
+
+# Workaround: Set primary display orientation to landscape
+ro.surface_flinger.primary_display_orientation=ORIENTATION_90
+
+# Workaround: Disable Bluetooth A2DP offload
+ro.bluetooth.a2dp_offload.supported=false
+persist.bluetooth.a2dp_offload.disabled=true
+```
+
+A backup is saved to `/system/build.prop.bak` before appending.
+
+## Usage
+
+1. Copy `CB-C6s-STU-GSI-Fixes.zip` to the device (sdcard or adb push).
+2. Boot to **TWRP Recovery**.
+3. Tap **Install** → select the zip → **Swipe to confirm Flash**.
+4. Reboot.
+
+The script mounts `/system` and `/vendor` automatically. No manual
+mounting is needed.
+
+## TWRP install output
+
+During flash, TWRP will show:
+
+```
+[1/3] Appending entries to /system/build.prop...
+[2/3] Installing goodix_ts.idc...
+[3/3] Installing sensor_config.xml...
+```
+
+## Compatibility
+
+- **Device**: CB-C6s-STU tablet (Spreadtrum / Unisoc platform)
+- **Recovery**: TWRP with `/sbin/sh` support (shell-script update-binary)
+- **GSI**: Any Android GSI that needs these device-specific tweaks
+
+## Notes
+
+- The `build.prop` entries are **appended, not replaced**. Re-flashing
+  the zip multiple times will duplicate the entries — restore from
+  `/system/build.prop.bak` if needed, or inspect the file first.
+- The `sensor_config.xml` covers four camera sensor combinations:
+  rear (`hi846`, `gc8034_rear`) and front (`hi846_front`, `gc8034`),
+  each with OTP EEPROM tuning parameters.
+- For SAR (System-as-Root) devices, the script falls back to
+  `/system/vendor/etc/` if `/vendor/etc/` is not available.
+
+## License
+
+Provided as-is for device maintenance. No warranty.