sys/storage: gate the sysfs device discovery to unix

src/core/utils/sys/storage.rs

@@ -1,17 +1,27 @@
 //! System utilities related to devices/peripherals
-
+//!
+//! Discovery reads sysfs under `/sys/dev/block/` and stats the device through
+//! `MetadataExt`, neither of which exists outside the unix family. Non-unix
+//! targets get arms that report nothing found, so callers need no condition of
+//! their own.
+
+use std::path::Path;
+#[cfg(unix)]
 use std::{
 	ffi::OsStr,
 	fs,
 	fs::{FileType, read_to_string},
-	path::{Path, PathBuf},
+	path::PathBuf,
 };
 
+#[cfg(unix)]
 use itertools::Itertools;
+#[cfg(unix)]
 use libc::dev_t;
 
+use crate::Result;
+#[cfg(unix)]
 use crate::{
-	Result,
 	result::FlatOk,
 	utils::{result::LogDebugErr, string::SplitInfallible},
 };
@@ -53,6 +63,7 @@ pub struct Queue {
 }
 
 /// Get properties of a MultiDevice (md) storage system
+#[cfg(unix)]
 #[must_use]
 pub fn md_discover(path: &Path) -> MultiDevice {
 	let dev_id = dev_from_path(path)
@@ -97,7 +108,16 @@ pub fn md_discover(path: &Path) -> MultiDevice {
 	}
 }
 
+/// Get properties of a MultiDevice (md) storage system.
+///
+/// Reports no raid on a target without sysfs, which is what the unix arm also
+/// returns for a path that is not on one.
+#[cfg(not(unix))]
+#[must_use]
+pub fn md_discover(_path: &Path) -> MultiDevice { MultiDevice::default() }
+
 /// Get properties of a MultiQueue within a MultiDevice.
+#[cfg(unix)]
 #[must_use]
 fn mq_discover(path: &Path) -> MultiQueue {
 	let mq_path = path.join("mq/");
@@ -129,6 +149,7 @@ fn mq_discover(path: &Path) -> MultiQueue {
 }
 
 /// Get properties of a Queue within a MultiQueue.
+#[cfg(unix)]
 fn queue_discover(dir: &Path) -> Queue {
 	let queue_id = dir.file_name();
 
@@ -161,6 +182,7 @@ fn queue_discover(dir: &Path) -> Queue {
 }
 
 /// Get the name of the block device on which Path is mounted.
+#[cfg(unix)]
 pub fn name_from_path(path: &Path) -> Result<String> {
 	use std::io::{Error, ErrorKind::NotFound};
 
@@ -177,9 +199,20 @@ pub fn name_from_path(path: &Path) -> Result<String> {
 		.map(Into::into)
 }
 
+/// Get the name of the block device on which Path is mounted.
+///
+/// Naming the device requires sysfs, so this reports the target cannot do it.
+/// The unix arm already returns an error when the name is not there to be read.
+#[cfg(not(unix))]
+pub fn name_from_path(_path: &Path) -> Result<String> {
+	use std::io::{Error, ErrorKind::Unsupported};
+
+	Err(Error::new(Unsupported, "Block device discovery requires sysfs.").into())
+}
+
 /// Get the (major, minor) of the block device on which Path is mounted.
+#[cfg(unix)]
 fn dev_from_path(path: &Path) -> Result<(dev_t, dev_t)> {
-	#[cfg(target_family = "unix")]
 	use std::os::unix::fs::MetadataExt;
 
 	let stat = fs::metadata(path)?;
@@ -210,6 +243,7 @@ fn dev_from_path(path: &Path) -> Result<(dev_t, dev_t)> {
 	Ok((major, minor))
 }
 
+#[cfg(unix)]
 fn block_path((major, minor): (dev_t, dev_t)) -> PathBuf {
 	format!("/sys/dev/block/{major}:{minor}/").into()
 }