========================
Display drivers and HAL
========================

The display slice of the vendor driver/HAL layer — split out from the
general HAL catalogue (:doc:`/userspace/drivers-hals`) because it belongs
next to the e-ink/display pages in this section (:doc:`stack`,
:doc:`tcon`).

One structural fact up front: **none of the Onyx-specific display drivers
are modules**. The e-ink EPDC and the LM3630A front-light are both built into
the kernel (``=y``; see :doc:`stack`), and there is no Onyx or EPD entry
in the VINTF manifest — the panel is driven through the custom ``/dev/ebc``
path, not a standard graphics HAL.

Everything here is from ``vendor_a.img`` (``lib/modules/``, ``bin/hw/``,
``lib64/hw/``, ``etc/vintf/manifest.xml``) read with ``7z``, cross-checked
against ``kernel_config.txt``. No code was executed.

Loadable kernel module
=======================

.. list-table::
   :header-rows: 1
   :widths: 26 74

   * - Module
     - Role / hardware
   * - ``lcd.ko``
     - the generic upstream LCD-class helper (a dependency of the built-in
       EPDC/backlight path — :doc:`stack`), **not** an Onyx driver

HAL services and implementations
=================================

.. list-table::
   :header-rows: 1
   :widths: 26 40 34

   * - HAL
     - Implementation
     - Hardware / cross-ref
   * - ``display.composer-service`` + ``display.allocator-service``
     - ``gralloc.lito.so``, ``graphics.mapper@{3,4}.0-impl-qti-display``
     - DPU/SDE compositor backing SurfaceFlinger; panel via EPDC
       (:doc:`stack`)
   * - ``lights-service.qti``
     - ``lights.lito.so``
     - notification LEDs (blue/red) + the front-light bridge (:doc:`stack`)

The GPU/NPU/media compute HALs (Vulkan, renderscript, neuralnetworks,
media.c2/omx) are cross-cutting rather than display-specific and stay in
:doc:`/userspace/drivers-hals`.

Provenance
==========

:Source: ``artifacts/super/vendor_a.img`` — ``lib/modules/{*.ko,modules.load}``
   (module set + boot load order), ``bin/hw/*`` and ``lib64/hw/*`` (HAL
   service and implementation libraries), ``etc/vintf/manifest.xml`` (HAL
   declaration); ``artifacts/boot_a/kernel_config.txt`` (built-in vs.
   modular).
:Method: ext4 image listed/extracted read-only with ``7z``; modules counted
   from ``modules.load``; HAL from ``bin/hw`` / ``lib64/hw`` names and the
   VINTF manifest. No code executed.
:Cross-refs: :doc:`stack` (built-in Onyx drivers, composer vs. EPDC),
   :doc:`tcon` (FPGA/TCON register-level detail),
   :doc:`/userspace/drivers-hals` (the rest of the HAL/module catalogue).