Add unstable-littlefs-patched feature

In #27, we updated littlefs to a patched version that backports a change
from littlefs v2.11 (filesystem shrinking) and adds a feature that has
not been merged upstream yet (config flag to disable block count check
on mount). To be able to cut a new release without rolling out these
changes to all users, this patch adds the new unstable-littlefs-patched
feature that enables these changes.

Author: robin-nitrokey

.github/workflows/ci.yml

@@ -41,7 +41,9 @@ jobs:
           cargo check --all-features
 
       - name: Build
-        run: cargo build --release --verbose
+        run: |
+          cargo build --release
+          cargo build --release --features unstable-littlefs
 
       - name: Run clippy
         if: matrix.target == 'x86_64-unknown-linux-gnu'

.gitmodules

@@ -1,3 +1,6 @@
 [submodule "littlefs"]
 	path = littlefs
+	url = https://github.com/ARMmbed/littlefs
+[submodule "littlefs-patched"]
+	path = littlefs-patched
 	url = https://github.com/trussed-dev/littlefs

CHANGELOG.md

@@ -9,6 +9,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Added
 
 - Derive `Default` if possible
+- Add `unstable-littlefs-patched` feature.  Enabling this feature may break semantic versioning guarantees. If this feature is enabled, a patched version of littlefs ([v2.9-trussed.1](https://github.com/trussed-dev/littlefs/releases/tag/v2.9-trussed.1)) is used with the following changes from v2.9.3:
+  - [Add config flag to disable block count check on mount](https://github.com/trussed-dev/littlefs/commit/5328ae4b2ad95088a8079c0dfbc623df45598a88)
+  - [Add support for shrinking a filesystem](https://github.com/trussed-dev/littlefs/commit/9a6ef46eb43e7edfdfdba04e50c602a8173b456c)
 
 ## [0.3.1] - 2025-02-27
 

Cargo.toml

@@ -19,3 +19,8 @@ trace = []
 malloc = []
 software-intrinsics = []
 multiversion = []
+
+# unstable features -- enabling one of the following features may break semantic versioning guarantees
+
+# use a patched version of littlefs: https://github.com/trussed-dev/littlefs/releases/tag/v2.9-trussed.1
+unstable-littlefs-patched = []

build.rs

@@ -2,6 +2,11 @@ use std::env;
 use std::path::PathBuf;
 
 fn main() -> Result<(), Box<dyn std::error::Error>> {
+    let littlefs_path = if cfg!(feature = "unstable-littlefs-patched") {
+        "littlefs-patched"
+    } else {
+        "littlefs"
+    };
     let out_path = PathBuf::from(env::var("OUT_DIR").unwrap());
 
     // Patch lfs.h to remove the lfs_util import because clang fails to locate the
@@ -10,8 +15,9 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
     // which comes as a distribution with these utils.
     // Turns out lfs_utils is not used in lfs.h, and clang properly finds stdint.h and stdbool,
     // but not string.h
-    let lfs_h = std::fs::read_to_string("littlefs/lfs.h").expect("Reading lfs.h succeeds");
-    println!("cargo::rerun-if-changed=littlefs/lfs.h");
+    let lfs_h =
+        std::fs::read_to_string(format!("{littlefs_path}/lfs.h")).expect("Reading lfs.h succeeds");
+    println!("cargo::rerun-if-changed={littlefs_path}/lfs.h");
     let out_lfs_h = out_path.join("lfs.h");
     std::fs::write(
         &out_lfs_h,
@@ -29,9 +35,9 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
         .flag("-DLFS_NO_WARN")
         .flag("-DLFS_NO_ERROR")
         .include(&out_path)
-        .include("littlefs")
-        .file("littlefs/lfs.c")
-        .file("littlefs/lfs_util.c")
+        .include(littlefs_path)
+        .file(format!("{littlefs_path}/lfs.c"))
+        .file(format!("{littlefs_path}/lfs_util.c"))
         .file("string.c");
 
     #[cfg(feature = "software-intrinsics")]