Add Intel Xe GPU driver support

[deveworld]

Summary

This PR adds support for Intel GPUs using the Xe kernel driver, which is required for newer hardware like Lunar Lake, Battlemage, and other recent Intel GPUs.

Closes #1407

Changes

• Add Xe namespace in btop_collect.cpp with PMU-based GPU monitoring
• Add minimal xe_drm.h header with UAPI definitions from Linux kernel
• Detect driver type (xe vs i915) and route to appropriate code path
• Dynamic PMU device discovery for discrete Intel GPUs (also addresses [BUG] Failed to find Intel GPU engines. Intel Arc A310. Linux x86_64 6.6.65 #938)

Implementation Approach

Per maintainer feedback on PR #1408, this implementation:

• Does NOT modify any files in src/linux/intel_gpu_top/ (IGT files)
• Adds Xe support entirely within the existing btop_collect.cpp structure
• Uses the same integration pattern as the existing i915 code

Supported Metrics (Xe driver)

Metric	Support	Source
GPU Utilization	✅	engine-active-ticks / engine-total-ticks PMU events
GPU Clock Speed	✅	gt-actual-frequency PMU event
Memory Usage	❌	Not available via PMU
Power Usage	❌	Not available via PMU
Temperature	❌	Not available via PMU

Testing

• ✅ Compiles successfully with make GPU_SUPPORT=true
• Tested only in Arc 130V.
• ⚠️ Needs testing on actual hardware (Arc A310, etc.)

Technical Notes

• Uses perf_event_open() syscall directly for PMU counter access
• Enumerates engines via DRM_IOCTL_XE_DEVICE_QUERY ioctl
• Reports max utilization across all GPU engines (render, copy, compute, etc.)
• Properly handles both integrated and discrete Intel GPUs with device-specific PMU names

[Copilot]

Pull request overview

This PR adds support for Intel GPUs using the Xe kernel driver, which is required for newer Intel hardware like Lunar Lake and Battlemage that don't use the legacy i915 driver.

Changes:

• Added minimal xe_drm.h header with UAPI definitions for interfacing with the Xe driver
• Implemented Xe namespace with PMU-based GPU monitoring using perf events
• Added dynamic driver detection and PMU device discovery to support both i915 and Xe drivers
• Routes collection to appropriate code path based on detected driver type

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 14 comments.

File	Description
src/linux/xe_drm.h	New header file containing minimal Xe DRM UAPI definitions (structs and ioctls) for device query and engine enumeration
src/linux/btop_collect.cpp	Added Xe namespace with PMU-based monitoring, dynamic driver detection, PMU device discovery, and routing logic to switch between i915 and Xe code paths

Comments suppressed due to low confidence (1)

src/linux/btop_collect.cpp:2103

• Missing free() call for gpu_path on error path. If get_intel_device_id() returns null, the function returns false without freeing gpu_path that was allocated by find_intel_gpu_dir().

			char *gpu_device_id = get_intel_device_id(gpu_path);
			if (!gpu_device_id) {
				Logger::debug("Failed to find Intel GPU device ID, Intel GPUs will not be detected");
				return false;

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[TheSovietPancakes]

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