Merge pull request #480 from maximevince/master

Add LFS_READONLY define, to allow smaller builds providing read-only mode

.travis.yml

@@ -208,6 +208,22 @@ jobs:
     script:
       - make test TFLAGS+="-k --valgrind"
 
+  # test compilation in read-only mode
+  - stage: test
+    env:
+      - NAME=littlefs-readonly
+      - CC="arm-linux-gnueabi-gcc --static -mthumb"
+      - CFLAGS="-Werror -DLFS_READONLY"
+    if: branch !~ -prefix$
+    install:
+      - *install-common
+      - sudo apt-get install
+            gcc-arm-linux-gnueabi
+            libc6-dev-armel-cross
+      - arm-linux-gnueabi-gcc --version
+    # report-size will compile littlefs and report the size
+    script: [*report-size]
+
   # self-host with littlefs-fuse for fuzz test
   - stage: test
     env:

lfs.c

@@ -140,6 +140,7 @@ static int lfs_bd_cmp(lfs_t *lfs,
     return LFS_CMP_EQ;
 }
 
+#ifndef LFS_READONLY
 static int lfs_bd_flush(lfs_t *lfs,
         lfs_cache_t *pcache, lfs_cache_t *rcache, bool validate) {
     if (pcache->block != LFS_BLOCK_NULL && pcache->block != LFS_BLOCK_INLINE) {
@@ -172,7 +173,9 @@ static int lfs_bd_flush(lfs_t *lfs,
 
     return 0;
 }
+#endif
 
+#ifndef LFS_READONLY
 static int lfs_bd_sync(lfs_t *lfs,
         lfs_cache_t *pcache, lfs_cache_t *rcache, bool validate) {
     lfs_cache_drop(lfs, rcache);
@@ -186,7 +189,9 @@ static int lfs_bd_sync(lfs_t *lfs,
     LFS_ASSERT(err <= 0);
     return err;
 }
+#endif
 
+#ifndef LFS_READONLY
 static int lfs_bd_prog(lfs_t *lfs,
         lfs_cache_t *pcache, lfs_cache_t *rcache, bool validate,
         lfs_block_t block, lfs_off_t off,
@@ -232,13 +237,16 @@ static int lfs_bd_prog(lfs_t *lfs,
 
     return 0;
 }
+#endif
 
+#ifndef LFS_READONLY
 static int lfs_bd_erase(lfs_t *lfs, lfs_block_t block) {
     LFS_ASSERT(block < lfs->cfg->block_count);
     int err = lfs->cfg->erase(lfs->cfg, block);
     LFS_ASSERT(err <= 0);
     return err;
 }
+#endif
 
 
 /// Small type-level utilities ///
@@ -392,10 +400,12 @@ static void lfs_ctz_fromle32(struct lfs_ctz *ctz) {
     ctz->size = lfs_fromle32(ctz->size);
 }
 
+#ifndef LFS_READONLY
 static void lfs_ctz_tole32(struct lfs_ctz *ctz) {
     ctz->head = lfs_tole32(ctz->head);
     ctz->size = lfs_tole32(ctz->size);
 }
+#endif
 
 static inline void lfs_superblock_fromle32(lfs_superblock_t *superblock) {
     superblock->version     = lfs_fromle32(superblock->version);
@@ -442,6 +452,7 @@ static inline void lfs_mlist_append(lfs_t *lfs, struct lfs_mlist *mlist) {
 
 
 /// Internal operations predeclared here ///
+#ifndef LFS_READONLY
 static int lfs_dir_commit(lfs_t *lfs, lfs_mdir_t *dir,
         const struct lfs_mattr *attrs, int attrcount);
 static int lfs_dir_compact(lfs_t *lfs,
@@ -458,10 +469,13 @@ static lfs_stag_t lfs_fs_parent(lfs_t *lfs, const lfs_block_t dir[2],
         lfs_mdir_t *parent);
 static int lfs_fs_relocate(lfs_t *lfs,
         const lfs_block_t oldpair[2], lfs_block_t newpair[2]);
+#endif
 int lfs_fs_traverseraw(lfs_t *lfs,
         int (*cb)(void *data, lfs_block_t block), void *data,
         bool includeorphans);
+#ifndef LFS_READONLY
 static int lfs_fs_forceconsistency(lfs_t *lfs);
+#endif
 static int lfs_deinit(lfs_t *lfs);
 #ifdef LFS_MIGRATE
 static int lfs1_traverse(lfs_t *lfs,
@@ -469,6 +483,7 @@ static int lfs1_traverse(lfs_t *lfs,
 #endif
 
 /// Block allocator ///
+#ifndef LFS_READONLY
 static int lfs_alloc_lookahead(void *p, lfs_block_t block) {
     lfs_t *lfs = (lfs_t*)p;
     lfs_block_t off = ((block - lfs->free.off)
@@ -480,6 +495,7 @@ static int lfs_alloc_lookahead(void *p, lfs_block_t block) {
 
     return 0;
 }
+#endif
 
 // indicate allocated blocks have been committed into the filesystem, this
 // is to prevent blocks from being garbage collected in the middle of a
@@ -496,6 +512,7 @@ static void lfs_alloc_drop(lfs_t *lfs) {
     lfs_alloc_ack(lfs);
 }
 
+#ifndef LFS_READONLY
 static int lfs_alloc(lfs_t *lfs, lfs_block_t *block) {
     while (true) {
         while (lfs->free.i != lfs->free.size) {
@@ -541,6 +558,7 @@ static int lfs_alloc(lfs_t *lfs, lfs_block_t *block) {
         }
     }
 }
+#endif
 
 /// Metadata pair and directory operations ///
 static lfs_stag_t lfs_dir_getslice(lfs_t *lfs, const lfs_mdir_t *dir,
@@ -673,6 +691,7 @@ static int lfs_dir_getread(lfs_t *lfs, const lfs_mdir_t *dir,
     return 0;
 }
 
+#ifndef LFS_READONLY
 static int lfs_dir_traverse_filter(void *p,
         lfs_tag_t tag, const void *buffer) {
     lfs_tag_t *filtertag = p;
@@ -700,7 +719,9 @@ static int lfs_dir_traverse_filter(void *p,
 
     return false;
 }
+#endif
 
+#ifndef LFS_READONLY
 static int lfs_dir_traverse(lfs_t *lfs,
         const lfs_mdir_t *dir, lfs_off_t off, lfs_tag_t ptag,
         const struct lfs_mattr *attrs, int attrcount,
@@ -794,6 +815,7 @@ static int lfs_dir_traverse(lfs_t *lfs,
         }
     }
 }
+#endif
 
 static lfs_stag_t lfs_dir_fetchmatch(lfs_t *lfs,
         lfs_mdir_t *dir, const lfs_block_t pair[2],
@@ -1233,6 +1255,7 @@ struct lfs_commit {
     lfs_off_t end;
 };
 
+#ifndef LFS_READONLY
 static int lfs_dir_commitprog(lfs_t *lfs, struct lfs_commit *commit,
         const void *buffer, lfs_size_t size) {
     int err = lfs_bd_prog(lfs,
@@ -1247,7 +1270,9 @@ static int lfs_dir_commitprog(lfs_t *lfs, struct lfs_commit *commit,
     commit->off += size;
     return 0;
 }
+#endif
 
+#ifndef LFS_READONLY
 static int lfs_dir_commitattr(lfs_t *lfs, struct lfs_commit *commit,
         lfs_tag_t tag, const void *buffer) {
     // check if we fit
@@ -1292,7 +1317,9 @@ static int lfs_dir_commitattr(lfs_t *lfs, struct lfs_commit *commit,
     commit->ptag = tag & 0x7fffffff;
     return 0;
 }
+#endif
 
+#ifndef LFS_READONLY
 static int lfs_dir_commitcrc(lfs_t *lfs, struct lfs_commit *commit) {
     // align to program units
     const lfs_off_t end = lfs_alignup(commit->off + 2*sizeof(uint32_t),
@@ -1392,7 +1419,9 @@ static int lfs_dir_commitcrc(lfs_t *lfs, struct lfs_commit *commit) {
 
     return 0;
 }
+#endif
 
+#ifndef LFS_READONLY
 static int lfs_dir_alloc(lfs_t *lfs, lfs_mdir_t *dir) {
     // allocate pair of dir blocks (backwards, so we write block 1 first)
     for (int i = 0; i < 2; i++) {
@@ -1430,7 +1459,9 @@ static int lfs_dir_alloc(lfs_t *lfs, lfs_mdir_t *dir) {
     // don't write out yet, let caller take care of that
     return 0;
 }
+#endif
 
+#ifndef LFS_READONLY
 static int lfs_dir_drop(lfs_t *lfs, lfs_mdir_t *dir, lfs_mdir_t *tail) {
     // steal state
     int err = lfs_dir_getgstate(lfs, tail, &lfs->gdelta);
@@ -1449,7 +1480,9 @@ static int lfs_dir_drop(lfs_t *lfs, lfs_mdir_t *dir, lfs_mdir_t *tail) {
 
     return 0;
 }
+#endif
 
+#ifndef LFS_READONLY
 static int lfs_dir_split(lfs_t *lfs,
         lfs_mdir_t *dir, const struct lfs_mattr *attrs, int attrcount,
         lfs_mdir_t *source, uint16_t split, uint16_t end) {
@@ -1482,7 +1515,9 @@ static int lfs_dir_split(lfs_t *lfs,
 
     return 0;
 }
+#endif
 
+#ifndef LFS_READONLY
 static int lfs_dir_commit_size(void *p, lfs_tag_t tag, const void *buffer) {
     lfs_size_t *size = p;
     (void)buffer;
@@ -1490,17 +1525,23 @@ static int lfs_dir_commit_size(void *p, lfs_tag_t tag, const void *buffer) {
     *size += lfs_tag_dsize(tag);
     return 0;
 }
+#endif
 
+#ifndef LFS_READONLY
 struct lfs_dir_commit_commit {
     lfs_t *lfs;
     struct lfs_commit *commit;
 };
+#endif
 
+#ifndef LFS_READONLY
 static int lfs_dir_commit_commit(void *p, lfs_tag_t tag, const void *buffer) {
     struct lfs_dir_commit_commit *commit = p;
     return lfs_dir_commitattr(commit->lfs, commit->commit, tag, buffer);
 }
+#endif
 
+#ifndef LFS_READONLY
 static int lfs_dir_compact(lfs_t *lfs,
         lfs_mdir_t *dir, const struct lfs_mattr *attrs, int attrcount,
         lfs_mdir_t *source, uint16_t begin, uint16_t end) {
@@ -1755,7 +1796,9 @@ relocate:
 
     return 0;
 }
+#endif
 
+#ifndef LFS_READONLY
 static int lfs_dir_commit(lfs_t *lfs, lfs_mdir_t *dir,
         const struct lfs_mattr *attrs, int attrcount) {
     // check for any inline files that aren't RAM backed and
@@ -1943,9 +1986,11 @@ compact:
 
     return 0;
 }
+#endif
 
 
 /// Top level directory operations ///
+#ifndef LFS_READONLY
 int lfs_mkdir(lfs_t *lfs, const char *path) {
     LFS_TRACE("lfs_mkdir(%p, \"%s\")", (void*)lfs, path);
     // deorphan if we haven't yet, needed at most once after poweron
@@ -2044,6 +2089,7 @@ int lfs_mkdir(lfs_t *lfs, const char *path) {
     LFS_TRACE("lfs_mkdir -> %d", 0);
     return 0;
 }
+#endif
 
 int lfs_dir_open(lfs_t *lfs, lfs_dir_t *dir, const char *path) {
     LFS_TRACE("lfs_dir_open(%p, %p, \"%s\")", (void*)lfs, (void*)dir, path);
@@ -2273,6 +2319,7 @@ static int lfs_ctz_find(lfs_t *lfs,
     return 0;
 }
 
+#ifndef LFS_READONLY
 static int lfs_ctz_extend(lfs_t *lfs,
         lfs_cache_t *pcache, lfs_cache_t *rcache,
         lfs_block_t head, lfs_size_t size,
@@ -2370,6 +2417,7 @@ relocate:
         lfs_cache_drop(lfs, pcache);
     }
 }
+#endif
 
 static int lfs_ctz_traverse(lfs_t *lfs,
         const lfs_cache_t *pcache, lfs_cache_t *rcache,
@@ -2425,6 +2473,9 @@ int lfs_file_opencfg(lfs_t *lfs, lfs_file_t *file,
             (void*)cfg, cfg->buffer, (void*)cfg->attrs, cfg->attr_count);
     LFS_ASSERT(!lfs_mlist_isopen(lfs->mlist, (struct lfs_mlist*)file));
 
+#ifdef LFS_READONLY
+    LFS_ASSERT((flags & 3) == LFS_O_RDONLY);
+#else
     // deorphan if we haven't yet, needed at most once after poweron
     if ((flags & LFS_O_RDWR) != LFS_O_RDONLY) {
         int err = lfs_fs_forceconsistency(lfs);
@@ -2433,6 +2484,7 @@ int lfs_file_opencfg(lfs_t *lfs, lfs_file_t *file,
             return err;
         }
     }
+#endif
 
     // setup simple file details
     int err;
@@ -2453,6 +2505,11 @@ int lfs_file_opencfg(lfs_t *lfs, lfs_file_t *file,
     file->type = LFS_TYPE_REG;
     lfs_mlist_append(lfs, (struct lfs_mlist *)file);
 
+#ifdef LFS_READONLY
+    if (tag == LFS_ERR_NOENT) {
+        err = LFS_ERR_NOENT;
+        goto cleanup;
+#else
     if (tag == LFS_ERR_NOENT) {
         if (!(flags & LFS_O_CREAT)) {
             err = LFS_ERR_NOENT;
@@ -2480,13 +2537,16 @@ int lfs_file_opencfg(lfs_t *lfs, lfs_file_t *file,
     } else if (flags & LFS_O_EXCL) {
         err = LFS_ERR_EXIST;
         goto cleanup;
+#endif
     } else if (lfs_tag_type3(tag) != LFS_TYPE_REG) {
         err = LFS_ERR_ISDIR;
         goto cleanup;
+#ifndef LFS_READONLY
     } else if (flags & LFS_O_TRUNC) {
         // truncate if requested
         tag = LFS_MKTAG(LFS_TYPE_INLINESTRUCT, file->id, 0);
         file->flags |= LFS_F_DIRTY;
+#endif
     } else {
         // try to load what's on disk, if it's inlined we'll fix it later
         tag = lfs_dir_get(lfs, &file->m, LFS_MKTAG(0x700, 0x3ff, 0),
@@ -2500,7 +2560,8 @@ int lfs_file_opencfg(lfs_t *lfs, lfs_file_t *file,
 
     // fetch attrs
     for (unsigned i = 0; i < file->cfg->attr_count; i++) {
-        if ((file->flags & LFS_O_RDWR) != LFS_O_WRONLY) {
+        // if opened for read / read-write operations
+        if ((file->flags & LFS_O_RDONLY) == LFS_O_RDONLY) {
             lfs_stag_t res = lfs_dir_get(lfs, &file->m,
                     LFS_MKTAG(0x7ff, 0x3ff, 0),
                     LFS_MKTAG(LFS_TYPE_USERATTR + file->cfg->attrs[i].type,
@@ -2512,7 +2573,9 @@ int lfs_file_opencfg(lfs_t *lfs, lfs_file_t *file,
             }
         }
 
-        if ((file->flags & LFS_O_RDWR) != LFS_O_RDONLY) {
+#ifndef LFS_READONLY
+        // if opened for write / read-write operations
+        if ((file->flags & LFS_O_WRONLY) == LFS_O_WRONLY) {
             if (file->cfg->attrs[i].size > lfs->attr_max) {
                 err = LFS_ERR_NOSPC;
                 goto cleanup;
@@ -2520,6 +2583,7 @@ int lfs_file_opencfg(lfs_t *lfs, lfs_file_t *file,
 
             file->flags |= LFS_F_DIRTY;
         }
+#endif
     }
 
     // allocate buffer if needed
@@ -2564,7 +2628,9 @@ int lfs_file_opencfg(lfs_t *lfs, lfs_file_t *file,
 
 cleanup:
     // clean up lingering resources
+#ifndef LFS_READONLY
     file->flags |= LFS_F_ERRED;
+#endif
     lfs_file_close(lfs, file);
     LFS_TRACE("lfs_file_opencfg -> %d", err);
     return err;
@@ -2584,7 +2650,11 @@ int lfs_file_close(lfs_t *lfs, lfs_file_t *file) {
     LFS_TRACE("lfs_file_close(%p, %p)", (void*)lfs, (void*)file);
     LFS_ASSERT(file->flags & LFS_F_OPENED);
 
+#ifdef LFS_READONLY
+    int err = 0;
+#else
     int err = lfs_file_sync(lfs, file);
+#endif
 
     // remove from list of mdirs
     lfs_mlist_remove(lfs, (struct lfs_mlist*)file);
@@ -2599,6 +2669,8 @@ int lfs_file_close(lfs_t *lfs, lfs_file_t *file) {
     return err;
 }
 
+
+#ifndef LFS_READONLY
 static int lfs_file_relocate(lfs_t *lfs, lfs_file_t *file) {
     LFS_ASSERT(file->flags & LFS_F_OPENED);
 
@@ -2669,7 +2741,9 @@ relocate:
         lfs_cache_drop(lfs, &lfs->pcache);
     }
 }
+#endif
 
+#ifndef LFS_READONLY
 static int lfs_file_outline(lfs_t *lfs, lfs_file_t *file) {
     file->off = file->pos;
     lfs_alloc_ack(lfs);
@@ -2681,7 +2755,9 @@ static int lfs_file_outline(lfs_t *lfs, lfs_file_t *file) {
     file->flags &= ~LFS_F_INLINE;
     return 0;
 }
+#endif
 
+#ifndef LFS_READONLY
 static int lfs_file_flush(lfs_t *lfs, lfs_file_t *file) {
     LFS_ASSERT(file->flags & LFS_F_OPENED);
 
@@ -2761,7 +2837,9 @@ relocate:
 
     return 0;
 }
+#endif
 
+#ifndef LFS_READONLY
 int lfs_file_sync(lfs_t *lfs, lfs_file_t *file) {
     LFS_TRACE("lfs_file_sync(%p, %p)", (void*)lfs, (void*)file);
     LFS_ASSERT(file->flags & LFS_F_OPENED);
@@ -2779,6 +2857,7 @@ int lfs_file_sync(lfs_t *lfs, lfs_file_t *file) {
         return err;
     }
 
+
     if ((file->flags & LFS_F_DIRTY) &&
             !lfs_pair_isnull(file->m.pair)) {
         // update dir entry
@@ -2818,17 +2897,21 @@ int lfs_file_sync(lfs_t *lfs, lfs_file_t *file) {
     LFS_TRACE("lfs_file_sync -> %d", 0);
     return 0;
 }
+#endif
 
 lfs_ssize_t lfs_file_read(lfs_t *lfs, lfs_file_t *file,
         void *buffer, lfs_size_t size) {
     LFS_TRACE("lfs_file_read(%p, %p, %p, %"PRIu32")",
             (void*)lfs, (void*)file, buffer, size);
     LFS_ASSERT(file->flags & LFS_F_OPENED);
+#ifndef LFS_READONLY
     LFS_ASSERT((file->flags & LFS_O_RDWR) != LFS_O_WRONLY);
+#endif
 
     uint8_t *data = buffer;
     lfs_size_t nsize = size;
 
+#ifndef LFS_READONLY
     if (file->flags & LFS_F_WRITING) {
         // flush out any writes
         int err = lfs_file_flush(lfs, file);
@@ -2837,6 +2920,7 @@ lfs_ssize_t lfs_file_read(lfs_t *lfs, lfs_file_t *file,
             return err;
         }
     }
+#endif
 
     if (file->pos >= file->ctz.size) {
         // eof if past end
@@ -2899,6 +2983,7 @@ lfs_ssize_t lfs_file_read(lfs_t *lfs, lfs_file_t *file,
     return size;
 }
 
+#ifndef LFS_READONLY
 lfs_ssize_t lfs_file_write(lfs_t *lfs, lfs_file_t *file,
         const void *buffer, lfs_size_t size) {
     LFS_TRACE("lfs_file_write(%p, %p, %p, %"PRIu32")",
@@ -3029,6 +3114,7 @@ relocate:
     LFS_TRACE("lfs_file_write -> %"PRId32, size);
     return size;
 }
+#endif
 
 lfs_soff_t lfs_file_seek(lfs_t *lfs, lfs_file_t *file,
         lfs_soff_t off, int whence) {
@@ -3036,12 +3122,14 @@ lfs_soff_t lfs_file_seek(lfs_t *lfs, lfs_file_t *file,
             (void*)lfs, (void*)file, off, whence);
     LFS_ASSERT(file->flags & LFS_F_OPENED);
 
+#ifndef LFS_READONLY
     // write out everything beforehand, may be noop if rdonly
     int err = lfs_file_flush(lfs, file);
     if (err) {
         LFS_TRACE("lfs_file_seek -> %d", err);
         return err;
     }
+#endif
 
     // find new pos
     lfs_off_t npos = file->pos;
@@ -3065,6 +3153,7 @@ lfs_soff_t lfs_file_seek(lfs_t *lfs, lfs_file_t *file,
     return npos;
 }
 
+#ifndef LFS_READONLY
 int lfs_file_truncate(lfs_t *lfs, lfs_file_t *file, lfs_off_t size) {
     LFS_TRACE("lfs_file_truncate(%p, %p, %"PRIu32")",
             (void*)lfs, (void*)file, size);
@@ -3128,6 +3217,7 @@ int lfs_file_truncate(lfs_t *lfs, lfs_file_t *file, lfs_off_t size) {
     LFS_TRACE("lfs_file_truncate -> %d", 0);
     return 0;
 }
+#endif
 
 lfs_soff_t lfs_file_tell(lfs_t *lfs, lfs_file_t *file) {
     LFS_TRACE("lfs_file_tell(%p, %p)", (void*)lfs, (void*)file);
@@ -3153,14 +3243,16 @@ lfs_soff_t lfs_file_size(lfs_t *lfs, lfs_file_t *file) {
     LFS_TRACE("lfs_file_size(%p, %p)", (void*)lfs, (void*)file);
     LFS_ASSERT(file->flags & LFS_F_OPENED);
     (void)lfs;
+
+#ifndef LFS_READONLY
     if (file->flags & LFS_F_WRITING) {
         LFS_TRACE("lfs_file_size -> %"PRId32,
                 lfs_max(file->pos, file->ctz.size));
         return lfs_max(file->pos, file->ctz.size);
-    } else {
-        LFS_TRACE("lfs_file_size -> %"PRId32, file->ctz.size);
-        return file->ctz.size;
     }
+#endif
+    LFS_TRACE("lfs_file_size -> %"PRId32, file->ctz.size);
+    return file->ctz.size;
 }
 
 
@@ -3179,8 +3271,10 @@ int lfs_stat(lfs_t *lfs, const char *path, struct lfs_info *info) {
     return err;
 }
 
+#ifndef LFS_READONLY
 int lfs_remove(lfs_t *lfs, const char *path) {
     LFS_TRACE("lfs_remove(%p, \"%s\")", (void*)lfs, path);
+
     // deorphan if we haven't yet, needed at most once after poweron
     int err = lfs_fs_forceconsistency(lfs);
     if (err) {
@@ -3259,7 +3353,9 @@ int lfs_remove(lfs_t *lfs, const char *path) {
     LFS_TRACE("lfs_remove -> %d", 0);
     return 0;
 }
+#endif
 
+#ifndef LFS_READONLY
 int lfs_rename(lfs_t *lfs, const char *oldpath, const char *newpath) {
     LFS_TRACE("lfs_rename(%p, \"%s\", \"%s\")", (void*)lfs, oldpath, newpath);
 
@@ -3404,6 +3500,7 @@ int lfs_rename(lfs_t *lfs, const char *oldpath, const char *newpath) {
     LFS_TRACE("lfs_rename -> %d", 0);
     return 0;
 }
+#endif
 
 lfs_ssize_t lfs_getattr(lfs_t *lfs, const char *path,
         uint8_t type, void *buffer, lfs_size_t size) {
@@ -3446,6 +3543,7 @@ lfs_ssize_t lfs_getattr(lfs_t *lfs, const char *path,
     return size;
 }
 
+#ifndef LFS_READONLY
 static int lfs_commitattr(lfs_t *lfs, const char *path,
         uint8_t type, const void *buffer, lfs_size_t size) {
     lfs_mdir_t cwd;
@@ -3467,7 +3565,9 @@ static int lfs_commitattr(lfs_t *lfs, const char *path,
     return lfs_dir_commit(lfs, &cwd, LFS_MKATTRS(
             {LFS_MKTAG(LFS_TYPE_USERATTR + type, id, size), buffer}));
 }
+#endif
 
+#ifndef LFS_READONLY
 int lfs_setattr(lfs_t *lfs, const char *path,
         uint8_t type, const void *buffer, lfs_size_t size) {
     LFS_TRACE("lfs_setattr(%p, \"%s\", %"PRIu8", %p, %"PRIu32")",
@@ -3481,13 +3581,16 @@ int lfs_setattr(lfs_t *lfs, const char *path,
     LFS_TRACE("lfs_setattr -> %d", err);
     return err;
 }
+#endif
 
+#ifndef LFS_READONLY
 int lfs_removeattr(lfs_t *lfs, const char *path, uint8_t type) {
     LFS_TRACE("lfs_removeattr(%p, \"%s\", %"PRIu8")", (void*)lfs, path, type);
     int err = lfs_commitattr(lfs, path, type, NULL, 0x3ff);
     LFS_TRACE("lfs_removeattr -> %d", err);
     return err;
 }
+#endif
 
 
 /// Filesystem operations ///
@@ -3615,6 +3718,7 @@ static int lfs_deinit(lfs_t *lfs) {
     return 0;
 }
 
+#ifndef LFS_READONLY
 int lfs_format(lfs_t *lfs, const struct lfs_config *cfg) {
     LFS_TRACE("lfs_format(%p, %p {.context=%p, "
                 ".read=%p, .prog=%p, .erase=%p, .sync=%p, "
@@ -3632,6 +3736,7 @@ int lfs_format(lfs_t *lfs, const struct lfs_config *cfg) {
             cfg->block_cycles, cfg->cache_size, cfg->lookahead_size,
             cfg->read_buffer, cfg->prog_buffer, cfg->lookahead_buffer,
             cfg->name_max, cfg->file_max, cfg->attr_max);
+
     int err = 0;
     {
         err = lfs_init(lfs, cfg);
@@ -3694,7 +3799,9 @@ cleanup:
     lfs_deinit(lfs);
     LFS_TRACE("lfs_format -> %d", err);
     return err;
+
 }
+#endif
 
 int lfs_mount(lfs_t *lfs, const struct lfs_config *cfg) {
     LFS_TRACE("lfs_mount(%p, %p {.context=%p, "
@@ -3921,6 +4028,7 @@ int lfs_fs_traverseraw(lfs_t *lfs,
         }
     }
 
+#ifndef LFS_READONLY
     // iterate over any open files
     for (lfs_file_t *f = (lfs_file_t*)lfs->mlist; f; f = f->next) {
         if (f->type != LFS_TYPE_REG) {
@@ -3943,6 +4051,7 @@ int lfs_fs_traverseraw(lfs_t *lfs,
             }
         }
     }
+#endif
 
     return 0;
 }
@@ -3956,6 +4065,7 @@ int lfs_fs_traverse(lfs_t *lfs,
     return err;
 }
 
+#ifndef LFS_READONLY
 static int lfs_fs_pred(lfs_t *lfs,
         const lfs_block_t pair[2], lfs_mdir_t *pdir) {
     // iterate over all directory directory entries
@@ -3981,12 +4091,16 @@ static int lfs_fs_pred(lfs_t *lfs,
 
     return LFS_ERR_NOENT;
 }
+#endif
 
+#ifndef LFS_READONLY
 struct lfs_fs_parent_match {
     lfs_t *lfs;
     const lfs_block_t pair[2];
 };
+#endif
 
+#ifndef LFS_READONLY
 static int lfs_fs_parent_match(void *data,
         lfs_tag_t tag, const void *buffer) {
     struct lfs_fs_parent_match *find = data;
@@ -4005,7 +4119,9 @@ static int lfs_fs_parent_match(void *data,
     lfs_pair_fromle32(child);
     return (lfs_pair_cmp(child, find->pair) == 0) ? LFS_CMP_EQ : LFS_CMP_LT;
 }
+#endif
 
+#ifndef LFS_READONLY
 static lfs_stag_t lfs_fs_parent(lfs_t *lfs, const lfs_block_t pair[2],
         lfs_mdir_t *parent) {
     // use fetchmatch with callback to find pairs
@@ -4032,7 +4148,9 @@ static lfs_stag_t lfs_fs_parent(lfs_t *lfs, const lfs_block_t pair[2],
 
     return LFS_ERR_NOENT;
 }
+#endif
 
+#ifndef LFS_READONLY
 static int lfs_fs_relocate(lfs_t *lfs,
         const lfs_block_t oldpair[2], lfs_block_t newpair[2]) {
     // update internal root
@@ -4127,14 +4245,18 @@ static int lfs_fs_relocate(lfs_t *lfs,
 
     return 0;
 }
+#endif
 
+#ifndef LFS_READONLY
 static void lfs_fs_preporphans(lfs_t *lfs, int8_t orphans) {
     LFS_ASSERT(lfs_tag_size(lfs->gstate.tag) > 0 || orphans >= 0);
     lfs->gstate.tag += orphans;
     lfs->gstate.tag = ((lfs->gstate.tag & ~LFS_MKTAG(0x800, 0, 0)) |
             ((uint32_t)lfs_gstate_hasorphans(&lfs->gstate) << 31));
 }
+#endif
 
+#ifndef LFS_READONLY
 static void lfs_fs_prepmove(lfs_t *lfs,
         uint16_t id, const lfs_block_t pair[2]) {
     lfs->gstate.tag = ((lfs->gstate.tag & ~LFS_MKTAG(0x7ff, 0x3ff, 0)) |
@@ -4142,7 +4264,9 @@ static void lfs_fs_prepmove(lfs_t *lfs,
     lfs->gstate.pair[0] = (id != 0x3ff) ? pair[0] : 0;
     lfs->gstate.pair[1] = (id != 0x3ff) ? pair[1] : 0;
 }
+#endif
 
+#ifndef LFS_READONLY
 static int lfs_fs_demove(lfs_t *lfs) {
     if (!lfs_gstate_hasmove(&lfs->gdisk)) {
         return 0;
@@ -4172,7 +4296,9 @@ static int lfs_fs_demove(lfs_t *lfs) {
 
     return 0;
 }
+#endif
 
+#ifndef LFS_READONLY
 static int lfs_fs_deorphan(lfs_t *lfs) {
     if (!lfs_gstate_hasorphans(&lfs->gstate)) {
         return 0;
@@ -4246,7 +4372,9 @@ static int lfs_fs_deorphan(lfs_t *lfs) {
     lfs_fs_preporphans(lfs, -lfs_gstate_getorphans(&lfs->gstate));
     return 0;
 }
+#endif
 
+#ifndef LFS_READONLY
 static int lfs_fs_forceconsistency(lfs_t *lfs) {
     int err = lfs_fs_demove(lfs);
     if (err) {
@@ -4260,6 +4388,7 @@ static int lfs_fs_forceconsistency(lfs_t *lfs) {
 
     return 0;
 }
+#endif
 
 static int lfs_fs_size_count(void *p, lfs_block_t block) {
     (void)block;

lfs.h

@@ -123,18 +123,24 @@ enum lfs_type {
 enum lfs_open_flags {
     // open flags
     LFS_O_RDONLY = 1,         // Open a file as read only
+#ifndef LFS_READONLY
     LFS_O_WRONLY = 2,         // Open a file as write only
     LFS_O_RDWR   = 3,         // Open a file as read and write
     LFS_O_CREAT  = 0x0100,    // Create a file if it does not exist
     LFS_O_EXCL   = 0x0200,    // Fail if a file already exists
     LFS_O_TRUNC  = 0x0400,    // Truncate the existing file to zero size
     LFS_O_APPEND = 0x0800,    // Move to end of file on every write
+#endif
 
     // internally used flags
+#ifndef LFS_READONLY
     LFS_F_DIRTY   = 0x010000, // File does not match storage
     LFS_F_WRITING = 0x020000, // File has been written since last flush
+#endif
     LFS_F_READING = 0x040000, // File has been read since last flush
-    LFS_F_ERRED   = 0x080000, // An error occured during write
+#ifndef LFS_READONLY
+    LFS_F_ERRED   = 0x080000, // An error occurred during write
+#endif
     LFS_F_INLINE  = 0x100000, // Currently inlined in directory entry
     LFS_F_OPENED  = 0x200000, // File has been opened
 };
@@ -399,6 +405,7 @@ typedef struct lfs {
 
 /// Filesystem functions ///
 
+#ifndef LFS_READONLY
 // Format a block device with the littlefs
 //
 // Requires a littlefs object and config struct. This clobbers the littlefs
@@ -407,6 +414,7 @@ typedef struct lfs {
 //
 // Returns a negative error code on failure.
 int lfs_format(lfs_t *lfs, const struct lfs_config *config);
+#endif
 
 // Mounts a littlefs
 //
@@ -426,12 +434,15 @@ int lfs_unmount(lfs_t *lfs);
 
 /// General operations ///
 
+#ifndef LFS_READONLY
 // Removes a file or directory
 //
 // If removing a directory, the directory must be empty.
 // Returns a negative error code on failure.
 int lfs_remove(lfs_t *lfs, const char *path);
+#endif
 
+#ifndef LFS_READONLY
 // Rename or move a file or directory
 //
 // If the destination exists, it must match the source in type.
@@ -439,6 +450,7 @@ int lfs_remove(lfs_t *lfs, const char *path);
 //
 // Returns a negative error code on failure.
 int lfs_rename(lfs_t *lfs, const char *oldpath, const char *newpath);
+#endif
 
 // Find info about a file or directory
 //
@@ -461,6 +473,7 @@ int lfs_stat(lfs_t *lfs, const char *path, struct lfs_info *info);
 lfs_ssize_t lfs_getattr(lfs_t *lfs, const char *path,
         uint8_t type, void *buffer, lfs_size_t size);
 
+#ifndef LFS_READONLY
 // Set custom attributes
 //
 // Custom attributes are uniquely identified by an 8-bit type and limited
@@ -470,13 +483,16 @@ lfs_ssize_t lfs_getattr(lfs_t *lfs, const char *path,
 // Returns a negative error code on failure.
 int lfs_setattr(lfs_t *lfs, const char *path,
         uint8_t type, const void *buffer, lfs_size_t size);
+#endif
 
+#ifndef LFS_READONLY
 // Removes a custom attribute
 //
 // If an attribute is not found, nothing happens.
 //
 // Returns a negative error code on failure.
 int lfs_removeattr(lfs_t *lfs, const char *path, uint8_t type);
+#endif
 
 
 /// File operations ///
@@ -525,6 +541,7 @@ int lfs_file_sync(lfs_t *lfs, lfs_file_t *file);
 lfs_ssize_t lfs_file_read(lfs_t *lfs, lfs_file_t *file,
         void *buffer, lfs_size_t size);
 
+#ifndef LFS_READONLY
 // Write data to file
 //
 // Takes a buffer and size indicating the data to write. The file will not
@@ -533,6 +550,7 @@ lfs_ssize_t lfs_file_read(lfs_t *lfs, lfs_file_t *file,
 // Returns the number of bytes written, or a negative error code on failure.
 lfs_ssize_t lfs_file_write(lfs_t *lfs, lfs_file_t *file,
         const void *buffer, lfs_size_t size);
+#endif
 
 // Change the position of the file
 //
@@ -541,10 +559,12 @@ lfs_ssize_t lfs_file_write(lfs_t *lfs, lfs_file_t *file,
 lfs_soff_t lfs_file_seek(lfs_t *lfs, lfs_file_t *file,
         lfs_soff_t off, int whence);
 
+#ifndef LFS_READONLY
 // Truncates the size of the file to the specified size
 //
 // Returns a negative error code on failure.
 int lfs_file_truncate(lfs_t *lfs, lfs_file_t *file, lfs_off_t size);
+#endif
 
 // Return the position of the file
 //
@@ -567,10 +587,12 @@ lfs_soff_t lfs_file_size(lfs_t *lfs, lfs_file_t *file);
 
 /// Directory operations ///
 
+#ifndef LFS_READONLY
 // Create a directory
 //
 // Returns a negative error code on failure.
 int lfs_mkdir(lfs_t *lfs, const char *path);
+#endif
 
 // Open a directory
 //
@@ -632,6 +654,7 @@ lfs_ssize_t lfs_fs_size(lfs_t *lfs);
 // Returns a negative error code on failure.
 int lfs_fs_traverse(lfs_t *lfs, int (*cb)(void*, lfs_block_t), void *data);
 
+#ifndef LFS_READONLY
 #ifdef LFS_MIGRATE
 // Attempts to migrate a previous version of littlefs
 //
@@ -646,6 +669,7 @@ int lfs_fs_traverse(lfs_t *lfs, int (*cb)(void*, lfs_block_t), void *data);
 // Returns a negative error code on failure.
 int lfs_migrate(lfs_t *lfs, const struct lfs_config *cfg);
 #endif
+#endif
 
 
 #ifdef __cplusplus