ghostdog: add subcommand detect-efa for EFA Device Detection

Signed-off-by: Yutong Sun <yutongsu@amazon.com>

Author: ytsssun

sources/Cargo.lock

@@ -13,6 +13,7 @@ argh.workspace = true
 gptman.workspace = true
 hex-literal.workspace = true
 lazy_static.workspace = true
+pciclient.workspace = true
 signpost.workspace = true
 snafu.workspace = true
 

sources/ghostdog/Cargo.toml

@@ -4,6 +4,7 @@ Current version: 0.1.0
 
 ghostdog is a tool to manage ephemeral disks.
 It can be called as a udev helper program to identify ephemeral disks.
+It can also be called for EFA device detection which can be used for ExecCondition in systemd units.
 
 ## Colophon
 

sources/ghostdog/README.md

@@ -1,6 +1,7 @@
 /*!
 ghostdog is a tool to manage ephemeral disks.
 It can be called as a udev helper program to identify ephemeral disks.
+It can also be called for EFA device detection which can be used for ExecCondition in systemd units.
 */
 
 use argh::FromArgs;
@@ -30,8 +31,14 @@ struct Args {
 enum SubCommand {
     Scan(ScanArgs),
     EbsDeviceName(EbsDeviceNameArgs),
+    EfaPresent(EfaPresentArgs),
 }
 
+#[derive(FromArgs, PartialEq, Debug)]
+#[argh(subcommand, name = "efa-present")]
+/// Detect if EFA devices are attached.
+struct EfaPresentArgs {}
+
 #[derive(FromArgs, PartialEq, Debug)]
 #[argh(subcommand, name = "scan")]
 /// Scan a device to see if it is an ephemeral disk.
@@ -63,10 +70,21 @@ fn run() -> Result<()> {
             let device_name = find_device_name(format!("{}", path.display()))?;
             emit_device_name(&device_name);
         }
+        SubCommand::EfaPresent(_) => {
+            is_efa_attached()?;
+        }
     }
     Ok(())
 }
 
+fn is_efa_attached() -> Result<()> {
+    if pciclient::is_efa_attached().context(error::CheckEfaFailureSnafu)? {
+        Ok(())
+    } else {
+        Err(error::Error::NoEfaPresent)
+    }
+}
+
 /// Find the device type by examining the partition table, if present.
 fn find_device_type<R>(reader: &mut R) -> Result<String>
 where
@@ -176,6 +194,10 @@ mod error {
         },
         #[snafu(display("Invalid device info for device '{}'", path.display()))]
         InvalidDeviceInfo { path: std::path::PathBuf },
+        #[snafu(display("Failed to check if EFA device is attached: {}", source))]
+        CheckEfaFailure { source: pciclient::PciClientError },
+        #[snafu(display("Did not detect EFA"))]
+        NoEfaPresent,
     }
 }