Validate CRC of incoming data

The data sent with Set_Report requests contains a CRC which we so far
ignored.  This patch adds a Crc struct that uses the CRC peripheral to
calculate the CRC for some data and uses it to validate the CRC of the
received data.

1 files changed, 40 insertions, 0 deletions

diff --git a/src/crc.rs b/src/crc.rs
new file mode 100644
index 0000000..cfcf982
--- /dev/null
+++ b/src/crc.rs
@@ -0,0 +1,40 @@
+// Copyright 2019 Robin Krahl <robin.krahl@ireas.org>
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+use hal::stm32::CRC;
+
+pub struct Crc {
+    crc: CRC,
+}
+
+impl Crc {
+    pub fn new(crc: CRC) -> Self {
+        Crc { crc }
+    }
+
+    pub fn get(&self, data: &[u8]) -> u32 {
+        self.reset();
+        data.chunks(4)
+            .map(slice_to_u32)
+            .for_each(|val| self.write(val));
+        self.read()
+    }
+
+    fn write(&self, val: u32) {
+        self.crc.dr.write(|w| w.dr().bits(val));
+    }
+
+    fn read(&self) -> u32 {
+        self.crc.dr.read().dr().bits()
+    }
+
+    fn reset(&self) {
+        self.crc.cr.write(|w| w.reset().reset());
+    }
+}
+
+fn slice_to_u32(data: &[u8]) -> u32 {
+    data.iter()
+        .enumerate()
+        .fold(0, |acc, (idx, val)| acc + (u32::from(*val) << (idx * 8)))
+}