The reiserfs filesystem was only enabled by the ethernut5 which appears to use jffs on nand for all default usecases (Nut/OS, Yocto) and doesn't have USB Storage support enabled, but does have MMC. It's also scheduled for removal in upstream Linux.
Looking at the logs for ethernut5 it doesn't actually appear to be actively maintained either for the best part of 10+ years but I don't remove that as part of this PR but leave it to someone who may know the AT91 ecosystem better than me.
Peter Robinson (2): configs: ethernut5: Drop reiserfs fs: drop reiserfs
cmd/Kconfig | 9 - cmd/reiser.c | 171 ------ configs/ethernut5_defconfig | 1 - fs/Kconfig | 2 - fs/Makefile | 1 - fs/reiserfs/Kconfig | 0 fs/reiserfs/Makefile | 10 - fs/reiserfs/dev.c | 28 - fs/reiserfs/mode_string.c | 124 ----- fs/reiserfs/reiserfs.c | 971 --------------------------------- fs/reiserfs/reiserfs_private.h | 509 ----------------- include/reiserfs.h | 72 --- 12 files changed, 1898 deletions(-) delete mode 100644 cmd/reiser.c delete mode 100644 fs/reiserfs/Kconfig delete mode 100644 fs/reiserfs/Makefile delete mode 100644 fs/reiserfs/dev.c delete mode 100644 fs/reiserfs/mode_string.c delete mode 100644 fs/reiserfs/reiserfs.c delete mode 100644 fs/reiserfs/reiserfs_private.h delete mode 100644 include/reiserfs.h