[feat]: add LG200 DRM device discovery

[guohuan78]

Summary

• discover LG200 DRM devices under /sys/class/drm using the loonggpu driver identity;
• expose a small C API for device enumeration and optional utilization/memory statistics;
• add lg200_info for runtime inspection;
• add a synthetic sysfs test that does not require Loongson hardware.

Scope

This PR contains device information retrieval only. It intentionally does not add an LG200 HwQueue, HwCommand, callback wrapper, scheduler policy, benchmark, model, or application demo.

Generic application work can continue to use XSched's existing HwCommandCreateCallback API. Hardware-specific KCD queue deactivation is being prepared as a separate Level-2 follow-up after this discovery layer is reviewed.

Build and test

cmake -S . -B build-lg200 \
  -DPLATFORM_LG200=ON \
  -DPLATFORM_OPENCL=ON \
  -DBUILD_TEST=ON
cmake --build build-lg200 --target lg200_info lg200_resource_test
./build-lg200/platforms/lg200/test/lg200_resource_test

Validation

• Ubuntu 24.04: hallg200, lg200_info, and lg200_resource_test build with -Wall -Wextra -Werror;
• synthetic DRM/sysfs enumeration test passes;
• public hal.h compiles as C11;
• git diff --check passes.

Validation run: https://github.com/guohuan78/xsched/actions/runs/30079872796

Runtime behavior

Lg200DeviceEnumerate() accepts the loonggpu driver name (or an explicit LG200 product identity) rather than treating the Loongson PCI vendor id alone as proof of a GPU. Statistics are optional: unavailable utilization is returned as -1.0, and unavailable memory counters as zero.

[Copilot]

Pull request overview

This PR introduces an LG200 “discovery-only” layer that enumerates Loongson LG200 DRM devices via sysfs and exposes a small C API for device listing and optional utilization/memory stats, plus a CLI/tool and a synthetic sysfs test to validate discovery without hardware.

Changes:

• Add Lg200DeviceEnumerate() / Lg200DeviceReadStats() C API and Linux sysfs-backed implementation.
• Add lg200_info tool for runtime inspection of discovered devices and optional stats.
• Add a synthetic /sys/class/drm-like test harness (lg200_resource_test) and wire up LG200 platform/test CMake.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
platforms/lg200/hal/src/resource.cpp	Implements sysfs-based DRM discovery and optional stats reads for LG200.
platforms/lg200/hal/include/xsched/lg200/hal.h	Defines the public LG200 C API structs and function declarations.
platforms/lg200/hal/include/xsched/lg200/hal/resource.h	Declares internal C++ discovery helper returning a std::vector.
platforms/lg200/tools/lg200_info.cpp	Adds a CLI utility to enumerate devices and print optional stats.
platforms/lg200/test/lg200_resource_test.cpp	Adds a synthetic sysfs/DRM layout test for discovery + stats behavior.
platforms/lg200/test/CMakeLists.txt	Builds and links the LG200 synthetic resource test on Linux.
platforms/lg200/CMakeLists.txt	Adds the LG200 HAL library, CLI tool, install rules, and test subdir hook.
platforms/lg200/README.md	Documents build steps and the LG200 discovery/statistics API behavior.

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