fix lint and add doc

Cargo.toml

@@ -11,7 +11,6 @@ members = [
     "crates/axfs_ramfs",
     "crates/axfs_vfs",
     "crates/axio",
-    "crates/eventfd",
     "crates/capability",
     "crates/crate_interface",
     "crates/driver_block",

crates/eventfd/src/lib.rs

@@ -1,37 +1,52 @@
-use bitflags::bitflags;
-
-bitflags! {
-    /// https://sites.uclouvain.be/SystInfo/usr/include/sys/eventfd.h.html
+/// The EventFd object to be used by syscall
+#![no_std]
+use core::convert::From;
+use core::convert::Into;
+
+bitflags::bitflags! {
+    /// The flags used to create an EventFd object
+    /// <https://sites.uclouvain.be/SystInfo/usr/include/sys/eventfd.h.html>
     #[derive(Clone, Copy, Debug)]
     pub struct EventFdFlag: u32 {
+        /// SEMAPHORE flag
         const EFD_SEMAPHORE = 0x1;
+        /// NONBLOCK flag
         const EFD_NONBLOCK  = 0x800;
+        /// CLOEXEC flag
         const EFD_CLOEXEC   = 0x80000;
     }
 }
 
+/// the result of writing to a EventFd object
 #[derive(Clone, Copy, Debug, PartialEq)]
 pub enum EventFdWriteResult {
+    /// the write is done successfully
     OK,
+
     /// an attempt is made to write the value 0xffffffffffffffff (f64::MAX)
     BadInput,
+
+    /// it's not writable yet
     NotReady,
 }
 
-/// https://man7.org/linux/man-pages/man2/eventfd2.2.html
+/// <https://man7.org/linux/man-pages/man2/eventfd2.2.html>
 pub struct EventFd {
     value: u64,
     flags: u32,
 }
 
+/// the EventFd data type
 impl EventFd {
+    /// create an EventFd object with initial value and flags
     pub fn new(initval: u64, flags: u32) -> EventFd {
         EventFd {
             value: initval,
             flags,
         }
     }
 
+    /// read the EventFd
     pub fn read(&mut self) -> Option<u64> {
         // If EFD_SEMAPHORE was not specified and the eventfd counter has a nonzero value, then a read returns 8 bytes containing that value,
         // and the counter's value is reset to zero.
@@ -54,6 +69,7 @@ impl EventFd {
         None
     }
 
+    /// write to EventFd
     pub fn write(&mut self, val: u64) -> EventFdWriteResult {
         if val == u64::MAX {
             return EventFdWriteResult::BadInput;
@@ -70,6 +86,7 @@ impl EventFd {
         }
     }
 
+    /// check if the specified flag is set or not
     pub fn is_flag_set(&self, flag: EventFdFlag) -> bool {
         self.flags & flag.bits() != 0
     }
@@ -79,21 +96,19 @@ impl EventFd {
     }
 }
 
-/// create eventfd with flags of zero default value
+/// create an EventFd object with flags of zero default value
 pub fn create_eventfd(value: u64) -> EventFd {
     value.into()
 }
 
+/// the util function to create an Eventfd object
 pub fn create_eventfd_with_flags(value: u64, flags: u32) -> EventFd {
     (value, flags).into()
 }
 
 impl From<u64> for EventFd {
     fn from(value: u64) -> Self {
-        EventFd {
-            value: value,
-            flags: 0,
-        }
+        EventFd { value, flags: 0 }
     }
 }