add smalldb flag, which builds a PDDB with a size of 4MiB

do not interchange this on devices with the full sized
PDDB, you may corrupt the database

services/pddb/Cargo.toml

@@ -88,4 +88,6 @@ hwtest = []
 # routines to help with performance profiling of the PDDB in hosted mode
 pddb-flamegraph = ["hex"]
 perfcounter = ["perflib"]
+# make the PDDB very small (4MiB). Note that booting a device with an incompatible `smalldb` setting will break the PDDB image. Use with caution.
+smalldb = []
 default = ["mbbb"]

services/pddb/src/api.rs

@@ -43,10 +43,10 @@ pub(crate) const PDDB_VERSION: u32 = 0x00_00_02_01;
 #[allow(dead_code)]
 // PDDB_A_LEN may be shorter than xous::PDDB_LEN, to speed up testing.
 #[allow(dead_code)]
-#[cfg(not(any(feature="pddbtest",feature="autobasis",feature="ci")))]
+#[cfg(not(any(feature="pddbtest",feature="autobasis",feature="ci",feature="smalldb")))]
 pub(crate) const PDDB_A_LEN: usize = xous::PDDB_LEN as usize;
 #[allow(dead_code)]
-#[cfg(any(feature="pddbtest",feature="autobasis",feature="ci"))]
+#[cfg(any(feature="pddbtest",feature="autobasis",feature="ci",feature="smalldb"))]
 pub const PDDB_A_LEN: usize = 4 * 1024 * 1024;
 
 /// range for the starting point of a journal number, picked from a random seed