Merge #70

70: Fix LineEvent timestamp doc r=eldruin a=mpi3d

Fix documentation on `LineEvent::timestamp()`.

According to the Linux documentation, the timestamp is `CLOCK_MONOTONIC` by default: [gpio.h#L286](https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/include/uapi/linux/gpio.h#n286).

Please see [#68 comment](#68 (comment)).

Co-authored-by: Matthieu CHARETTE <[email protected]>

Author: bors[bot]

src/lib.rs

@@ -920,8 +920,10 @@ impl LineEvent {
     /// in an interrupt handler so it should be very accurate.
     ///
     /// The nanosecond timestamp value should are captured
-    /// using the `CLOCK_REALTIME` offsets in the kernel and
-    /// should be compared against `CLOCK_REALTIME` values.
+    /// using the `CLOCK_MONOTONIC` offsets in the kernel and
+    /// should be compared against `CLOCK_MONOTONIC` values.
+    /// Note that kernel versions prior to 5.7 used
+    /// `CLOCK_REALTIME` offsets instead.
     pub fn timestamp(&self) -> u64 {
         self.0.timestamp
     }