Make GPU support optional to enable RISC-V builds without libdrm

- Add 'gpu' feature flag (enabled by default)
- Make gfxinfo dependency optional
- Provide no-op GPU metrics when gpu feature disabled
- Disable GPU support for RISC-V builds in CI (libdrm unavailable)
- All other architectures (amd64, arm64, armhf) still get GPU support

.github/workflows/build-deb.yml

@@ -115,10 +115,16 @@ jobs:
         run: |
           cargo deb --package socktop --target ${{ matrix.target }} --no-strip
 
-      - name: Build socktop_agent .deb package
+      - name: Build socktop_agent .deb package (with GPU support)
+        if: matrix.target != 'riscv64gc-unknown-linux-gnu'
         run: |
           cargo deb --package socktop_agent --target ${{ matrix.target }} --no-strip
 
+      - name: Build socktop_agent .deb package (without GPU support for RISC-V)
+        if: matrix.target == 'riscv64gc-unknown-linux-gnu'
+        run: |
+          cargo deb --package socktop_agent --target ${{ matrix.target }} --no-strip --no-default-features
+
       - name: Copy packages to debs directory
         run: |
           mkdir -p debs

socktop_agent/Cargo.toml

@@ -23,7 +23,7 @@ flate2 = { version = "1", default-features = false, features = ["rust_backend"]
 futures-util = "0.3.31"
 tracing = { version = "0.1", optional = true }
 tracing-subscriber = { version = "0.3", features = ["env-filter"], optional = true }
-gfxinfo = "0.1.2"
+gfxinfo = { version = "0.1.2", optional = true }
 once_cell = "1.19"
 axum-server = { version = "0.7", features = ["tls-rustls"] }
 rustls = { version = "0.23", features = ["aws-lc-rs"] }
@@ -35,7 +35,8 @@ prost = { workspace = true }
 time = { version = "0.3", default-features = false, features = ["formatting", "macros", "parsing" ] }
 
 [features]
-default = []
+default = ["gpu"]
+gpu = ["gfxinfo"]
 logging = ["tracing", "tracing-subscriber"]
 
 [build-dependencies]

socktop_agent/src/gpu.rs

@@ -1,4 +1,5 @@
 // gpu.rs
+#[cfg(feature = "gpu")]
 use gfxinfo::active_gpu;
 
 #[derive(Debug, Clone, serde::Serialize)]
@@ -9,6 +10,7 @@ pub struct GpuMetrics {
     pub mem_total_bytes: u64,
 }
 
+#[cfg(feature = "gpu")]
 pub fn collect_all_gpus() -> Result<Vec<GpuMetrics>, Box<dyn std::error::Error>> {
     let gpu = active_gpu()?; // Use ? to unwrap Result
     let info = gpu.info();
@@ -22,3 +24,9 @@ pub fn collect_all_gpus() -> Result<Vec<GpuMetrics>, Box<dyn std::error::Error>>
 
     Ok(vec![metrics])
 }
+
+#[cfg(not(feature = "gpu"))]
+pub fn collect_all_gpus() -> Result<Vec<GpuMetrics>, Box<dyn std::error::Error>> {
+    // GPU support not available on this platform
+    Ok(vec![])
+}