Sprint 13 — Intel Expansion

Goal: Prove that the PlayOS architecture, compositor, and playos-platform-api backend model are portable to Intel graphics hardware. The compositor selects the correct GPU by PCI enumeration, not by a hardcoded device path. A second libplayos input/graphics backend compiles and runs on an Intel PC.

Primary Outcome: PlayOS boots and runs the full shell + game lifecycle on an Intel-graphics PC (NUC, laptop, or similar). No code path is hardcoded to AMD. The playos-platform-api backend abstraction is validated as truly portable.

Prerequisites: Sprint 12 complete — AMD implementation complete and hardened.

Why This Sprint Exists

Sprint 12 hardened the AMD ROG Ally path, but that success is still a single-vendor result. The compositor already enumerates DRM devices and selects by PCI identity (Sprint 4), so the question this sprint answers is whether that selection logic, the backend model, and the Buildroot image pipeline generalize without AMD-specific assumptions creeping back in. A second hardware target also forces the platform API to earn its abstraction: if Intel bring-up requires changes to the public headers or to the compositor's device-selection logic, the abstraction is not real yet. This sprint validates portability and produces a second supported target.

Start Condition Checklist

• Sprint 12 complete: the AMD implementation is hardened and all AMD acceptance criteria pass.
• The compositor already enumerates DRM devices and selects by PCI identity (Sprint 4 deliverable).
• The supported vendor IDs are defined: PCI_VENDOR_AMD 0x1002, PCI_VENDOR_INTEL 0x8086.
• The GPU selection fallback order is documented and implemented: active connector → AMD → Intel → first valid DRM device → fatal.
• An Intel-graphics PC (NUC, laptop, or test machine) is available for device tests.
• The AMD ROG Ally smoke-test checklist is current and repeatable for regression use.

Decisions Locked for This Sprint

• GPU selection fallback order: active display connector → AMD (primary when multiple GPUs) → Intel → first valid DRM device → fatal if none found.
• No hardcoded paths: card0, amdgpu, or vendor-specific strings must not appear in the compositor or in libplayos public API.
• Intel kernel: use CONFIG_DRM_I915 or CONFIG_DRM_XE depending on target hardware generation; disable AMD-only configs in the Intel defconfig.
• Intel audio: CONFIG_SND_HDA_INTEL plus Intel-specific codecs.
• Intel power: CONFIG_X86_INTEL_PSTATE and CONFIG_INTEL_RAPL.
• Mesa backend: gallium-drivers=iris for Gen 9+ (i965 for older); Intel Vulkan (ANV) is deferred to a future Vulkan sprint.
• Backend selection: playos-platform-api selects its backend at runtime via the PLAYOS_BACKEND environment variable, with a hardware-agnostic evdev input path and a PCI-vendor-based GPU query path.
• Power interface: playos_power_request_profile() stays hardware-agnostic on the EPP sysfs interface.

Scope

In Scope

• Validate the existing PCI-based GPU discovery logic against Intel hardware.
• Add an Intel PC Buildroot defconfig with Intel kernel, audio, power, and firmware options.
• Enable the Mesa Iris Gallium backend for Intel and verify hardware acceleration.
• Formalize the internal PlayOSInputBackend abstraction and PLAYOS_BACKEND selection.
• Validate playos_power_get_info() and profile requests against Intel sysfs paths.
• Add make intel-config, make intel-build, and make intel-usb-image targets.
• Validate all three sample games on the Intel PC.
• Document the dual-vendor support matrix and backend portability guidance.

Explicitly Out of Scope

• Intel Vulkan (ANV) — deferred to a future Vulkan sprint.
• Runtime testing of Intel hardware in CI — Intel device tests are device-only; CI covers cross-compilation.
• Automatic backend auto-detection beyond the documented env-var and PCI-vendor paths.
• Multi-GPU simultaneous rendering (one active GPU is selected; the other is ignored).

Required Repository Changes

Expected Files and Directories

playos-compositor

src/gpu_select.c                # PCI vendor selection, fallback order, selected-vendor logging
src/compositor.c                # consumes the selected DRM device; no card0/vendor strings
tests/test_gpu_select.c         # fallback-order unit test with fake DRM/vendor data

playos-platform-api

src/input_backend.c             # PlayOSInputBackend dispatch via PLAYOS_BACKEND env var
src/power_intel.c               # Intel power sysfs queries (coretemp, GPU hwmon, EPP)
src/playos_system.c             # device-model string: non-AMD value on Intel targets

playos-refdistro

br2-external/configs/playos_intel_pc_defconfig
br2-external/board/intel/linux-fragment.cfg   # DRM_I915/XE, SND_HDA_INTEL, INTEL_PSTATE, INTEL_RAPL
br2-external/board/intel/firmware.list        # i915 firmware blobs
Makefile                                      # make intel-config / intel-build / intel-usb-image
gen-intel-usb-image.sh                        # USB-bootable Intel PC image

playos-samples

docs/intel-portability-validation.md   # per-game Intel results: render, input, audio, lifecycle

playos-spec

src/hardware-matrix.md          # updated: AMD ROG Ally + Intel PC supported targets
src/backend-portability.md      # new: backend model, PLAYOS_BACKEND, power sysfs matrix
src/sprints/Sprint-13.md        # this sprint

Agent Task Breakdown

Task Status Grid

Update the Status column as work progresses: not started → in progress → blocked or done.

S13-T1 — Validate GPU discovery by PCI vendor

The compositor already enumerates DRM devices and selects by PCI identity (Sprint 4). Verify on Intel hardware that the selection logic picks the Intel device without code changes. Enforce the fallback order — active connector → AMD → Intel → first valid DRM device → fatal — and log the selected vendor ID, device ID, and device path. Confirm no card0 or vendor-specific hardcoding remains.

Done when: the compositor log shows the Intel vendor ID (0x8086) and device path on an Intel PC, the fallback-order unit test passes with synthetic multi-GPU data, and a grep of playos-compositor finds no card0 hardcoding.

S13-T2 — Add Intel PC kernel configuration

Create br2-external/configs/playos_intel_pc_defconfig from a known Intel-compatible configuration. Add Intel GPU support (CONFIG_DRM_I915 or CONFIG_DRM_XE depending on target generation), Intel audio (CONFIG_SND_HDA_INTEL plus codecs), and Intel power options (CONFIG_X86_INTEL_PSTATE, CONFIG_INTEL_RAPL). Include the i915/ firmware blobs. Disable AMD-only configs (CONFIG_DRM_AMDGPU, CONFIG_X86_AMD_PSTATE) in the Intel defconfig.

Done when: the Intel defconfig builds a kernel where the required Intel config symbols are enabled and the AMD-only symbols are disabled, as shown by the generated .config.

S13-T3 — Enable Mesa Iris backend

Configure Buildroot Mesa with gallium-drivers=iris for Intel Gen 9+ (or i965 for older), keeping GBM, EGL, and OpenGL ES the same as the AMD config. Intel Vulkan (ANV) is deferred. Verify at runtime that Mesa reports an Intel renderer.

Done when: on an Intel PC, Mesa initialization logs Mesa ... on Intel ... (or the equivalent Intel renderer string), and sample-triangle renders with hardware acceleration rather than a software fallback.

S13-T4 — Formalize PlayOSInputBackend

Define the internal backend struct in playos-platform-api/src/ with name, init, get_controller_state, and shutdown members, and dispatch at runtime from the PLAYOS_BACKEND environment variable. The evdev input path remains hardware-agnostic and works unchanged; GPU info queries select by PCI vendor via playos_system.h. Public headers must not change to support the second backend.

Done when: setting PLAYOS_BACKEND selects the requested backend without recompiling public headers, and the AMD backend continues to pass its existing tests unchanged.

S13-T5 — Validate Intel power sysfs paths

Verify the Intel power sysfs paths: CPU temperature via the coretemp thermal zone, GPU temperature via /sys/class/drm/card*/device/hwmon/hwmon*/temp1_input, power profile via /sys/devices/system/cpu/cpu0/cpufreq/energy_performance_preference (the same EPP interface as AMD P-state), and battery via /sys/class/power_supply/BAT*/. Confirm playos_power_request_profile() works on Intel without modification.

Done when: playos_power_get_info() returns valid CPU and battery data on the Intel PC, and playos_system_device_model() returns a non-AMD device string.

S13-T6 — Add make intel-* targets

Add make intel-config, make intel-build, and make intel-usb-image to the playos-refdistro Makefile, plus a gen-intel-usb-image.sh for a USB-bootable Intel PC image. Wire the Intel build into CI as a cross-compilation target.

Done when: make intel-build compiles cleanly in CI and produces the Intel image artifacts alongside the existing AMD artifacts.

S13-T7 — Validate sample-game portability

Run sample-triangle, sample-input, and sample-audio on the Intel PC and confirm hardware-accelerated rendering, controller input (USB gamepad if no built-in controller), audio output, and the system-button/lifecycle flow. Record the results in docs/intel-portability-validation.md.

Done when: all three sample games run on the Intel PC with the same behavior as on AMD, and the portability validation document is committed with per-game evidence.

S13-T8 — Document dual-vendor support

Update the supported-hardware matrix to list both the AMD ROG Ally and the Intel PC, and add backend-portability guidance covering the PlayOSInputBackend model, PLAYOS_BACKEND, GPU selection fallback order, and the power sysfs matrix.

Done when: hardware-matrix.md lists both targets and backend-portability.md is committed and linked from the spec index.

Implementation Guidance

Validate, don't rewrite, the selection logic. The GPU selection already exists from Sprint 4. The goal is to prove it generalizes — add logging and a test, not a second selection path.

No vendor strings in the public API. If Intel support requires a change to playos-platform-api public headers, the abstraction has failed; fix the abstraction instead.

Keep CI compile-only for Intel. Intel runtime tests are device-only. CI validates that the Intel defconfig cross-compiles; do not gate the sprint on Intel hardware in CI.

Disable, don't just omit, AMD options. The Intel defconfig must explicitly disable CONFIG_DRM_AMDGPU and CONFIG_X86_AMD_PSTATE so the result is unambiguous.

Preserve the EPP power interface. Do not fork the power API per vendor; the energy-performance-preference sysfs interface is shared and should stay shared.

Treat Intel Vulkan as explicitly deferred. Do not pull ANV into this sprint's scope; record it as a future-sprint follow-up only.

Verification and Evidence

Acceptance Criteria

• PlayOS boots on an Intel-graphics PC (NUC, laptop, or test machine)
• Compositor selects the Intel DRM device by PCI enumeration (no hardcoded path)
• Compositor log shows Intel vendor ID and Mesa Iris (or i965) renderer
• sample-triangle runs with hardware acceleration on Intel (Mesa reports Intel ...)
• sample-input receives controller input on Intel PC (USB gamepad or built-in)
• sample-audio plays audio on Intel PC
• System button and lifecycle flow works on Intel PC
• playos_power_get_info() returns valid CPU and battery data on Intel
• playos_system_device_model() returns a non-AMD device string
• AMD ROG Ally tests are unaffected — all Sprint 12 acceptance criteria still pass
• No card0, amdgpu, or AMD-specific hardcoded strings in compositor or libplayos public API
• make intel-build succeeds in CI (using a cross-compilation target)

Handoff to Sprint 14

Sprint 14 may assume:

• PlayOS runs the full console lifecycle on both the AMD ROG Ally and an Intel PC.
• The compositor selects the GPU by PCI enumeration with a tested fallback order and no hardcoded paths.
• The playos-platform-api backend model is validated as portable via PlayOSInputBackend and PLAYOS_BACKEND.
• The Mesa Intel (Iris) backend is enabled and hardware acceleration is verified.
• make intel-build and make intel-usb-image targets exist and compile in CI.
• The supported-hardware matrix and backend-portability docs are committed.

Exit Gate

PlayOS runs the full console lifecycle on an Intel-graphics PC. No hardcoded AMD/Intel paths remain in the compositor or libplayos. The playos-platform-api backend model is validated as portable.

Previous: Sprint 12 | Next: Sprint 14