make build BOARD=k210 sucessfully

os/src/fs/stdio.rs

@@ -1,6 +1,12 @@
 use super::File;
-use crate::drivers::chardev::{CharDevice, UART};
+use crate::drivers::chardev::CharDevice;
+#[cfg(feature = "board_qemu")]
+use crate::drivers::chardev::UART;
 use crate::mm::UserBuffer;
+#[cfg(feature = "board_k210")]
+use crate::sbi::console_getchar;
+#[cfg(feature = "board_k210")]
+use crate::task::suspend_current_and_run_next;
 
 pub struct Stdin;
 pub struct Stdout;
@@ -12,6 +18,7 @@ impl File for Stdin {
     fn writable(&self) -> bool {
         false
     }
+    #[cfg(feature = "board_qemu")]
     fn read(&self, mut user_buf: UserBuffer) -> usize {
         assert_eq!(user_buf.len(), 1);
         //println!("before UART.read() in Stdin::read()");
@@ -21,6 +28,27 @@ impl File for Stdin {
         }
         1
     }
+    #[cfg(feature = "board_k210")]
+    fn read(&self, mut user_buf: UserBuffer) -> usize {
+        assert_eq!(user_buf.len(), 1);
+        // busy loop
+        let mut c: usize;
+        loop {
+            c = console_getchar();
+            if c == 0 {
+                suspend_current_and_run_next();
+                continue;
+            } else {
+                break;
+            }
+        }
+        let ch = c as u8;
+        unsafe {
+            user_buf.buffers[0].as_mut_ptr().write_volatile(ch);
+        }
+        1
+    }
+
     fn write(&self, _user_buf: UserBuffer) -> usize {
         panic!("Cannot write to stdin!");
     }