floss: fix some rust warnings

* Add serde feature in hcidoc_packets (the generated files has serde
  configuration feature)
* Allow dead code in hcidoc parser (the structs correctly represent
  the actual packet despite the value is never read)
* Don't use DateTime::from_timestamp_micros in hcidoc parser because
  it needs chrono version above what's available on our rust_crates
* Use underscore for default match arm
* Remove unused FromPrimitive trait

Bug: None
Test: m -j
Flag: EXEMPT, floss only changes
Change-Id: Ie81c021b02ca5fa7d142fc64e8cec061c6566f2c

4 files changed, 17 insertions, 3 deletions

diff --git a/floss/hcidoc/packets/Cargo.toml b/floss/hcidoc/packets/Cargo.toml
index cd633bb88c..0b65fa4b26 100644
--- a/floss/hcidoc/packets/Cargo.toml
+++ b/floss/hcidoc/packets/Cargo.toml
@@ -37,3 +37,6 @@ walkdir = "2.2"
 [lib]
 path = "lib.rs"
 crate-type = ["rlib"]
+
+[features]
+serde = []
diff --git a/floss/hcidoc/src/parser.rs b/floss/hcidoc/src/parser.rs
index 26659bc424..572040cabe 100644
--- a/floss/hcidoc/src/parser.rs
+++ b/floss/hcidoc/src/parser.rs
@@ -103,6 +103,7 @@ const SNOOP_Y0_TO_Y1970_US: i64 = 62_168_256_000_000_000;
 
 /// Snoop file packet format.
 #[derive(Debug, Clone)]
+#[allow(dead_code)]
 pub struct SnoopPacketPreamble {
     /// The original length of the captured packet as received via a network.
     pub original_length: u32,
@@ -177,7 +178,15 @@ pub trait GeneralSnoopPacket {
     fn get_timestamp(&self) -> Option<NaiveDateTime> {
         let preamble = self.preamble();
         let ts_i64 = i64::try_from(preamble.timestamp_us).unwrap_or(i64::MAX);
-        DateTime::from_timestamp_micros(ts_i64 - SNOOP_Y0_TO_Y1970_US).map(|date| date.naive_utc())
+
+        // TODO: directly use Datetime::from_timestamp_micros() once chrono package is re-vendored
+        //       to v0.4.35. Below is the actual implementation of that function.
+        let from_timestamp_micros = |micros: i64| -> Option<DateTime<_>> {
+            let secs = micros.div_euclid(1_000_000);
+            let nsecs = micros.rem_euclid(1_000_000) as u32 * 1000;
+            DateTime::from_timestamp(secs, nsecs)
+        };
+        from_timestamp_micros(ts_i64 - SNOOP_Y0_TO_Y1970_US).map(|date| date.naive_utc())
     }
 }
 
@@ -420,6 +429,7 @@ impl<'a> TryFrom<&'a dyn GeneralSnoopPacket> for PacketChild {
 
 /// A single processable packet of data.
 #[derive(Debug, Clone)]
+#[allow(dead_code)]
 pub struct Packet {
     /// Timestamp of this packet
     pub ts: NaiveDateTime,
@@ -454,6 +464,7 @@ impl<'a> TryFrom<(usize, &'a dyn GeneralSnoopPacket)> for Packet {
     }
 }
 
+#[allow(dead_code)]
 pub enum AclContent {
     Control(Control),
     LeControl(LeControl),
diff --git a/system/gd/rust/topshim/src/btif.rs b/system/gd/rust/topshim/src/btif.rs
index b5df64fb7e..b7e8dbbac6 100644
--- a/system/gd/rust/topshim/src/btif.rs
+++ b/system/gd/rust/topshim/src/btif.rs
@@ -435,7 +435,7 @@ impl ToString for BtVendorProductInfo {
             match self.vendor_id_src {
                 1 => "bluetooth",
                 2 => "usb",
-                default => "unknown",
+                _ => "unknown",
             },
             self.vendor_id,
             self.product_id,
diff --git a/system/gd/rust/topshim/src/syslog.rs b/system/gd/rust/topshim/src/syslog.rs
index 5af01c4948..628d6682c4 100644
--- a/system/gd/rust/topshim/src/syslog.rs
+++ b/system/gd/rust/topshim/src/syslog.rs
@@ -5,7 +5,7 @@
 //! to tune log levels for syslog.
 
 use num_derive::{FromPrimitive, ToPrimitive};
-use num_traits::cast::{FromPrimitive, ToPrimitive};
+use num_traits::cast::ToPrimitive;
 use std::ffi::CString;
 use std::os::raw::c_char;