diff --git a/crate/bbl/src/sbi.rs b/crate/bbl/src/sbi.rs
index b8782b7..87007cd 100644
--- a/crate/bbl/src/sbi.rs
+++ b/crate/bbl/src/sbi.rs
@@ -1,5 +1,13 @@
 //! Port from sbi.h
+//! 
+//! This code is used for OS to use hardware outside with calling these implements
 
+/*
+**  @brief  translate implement calling message to RISCV asm
+**  @param  which: usize                ecall type
+**          arg0, arg1, arg2: usize     ecall args
+**  @retval ret: usize                  the result of the asm
+*/
 #[inline(always)]
 fn sbi_call(which: usize, arg0: usize, arg1: usize, arg2: usize) -> usize {
     let ret;
@@ -13,18 +21,38 @@ fn sbi_call(which: usize, arg0: usize, arg1: usize, arg2: usize) -> usize {
     ret
 }
 
+/*
+**  @brief  output char to console
+**  @param  ch: usize       the char to output to console
+**  @retval none
+*/
 pub fn console_putchar(ch: usize) {
     sbi_call(SBI_CONSOLE_PUTCHAR, ch, 0, 0);
 }
 
+/*
+**  @brief  input char from console
+**  @param  none
+**  @retval ch: usize       the char get from console
+*/
 pub fn console_getchar() -> usize {
     sbi_call(SBI_CONSOLE_GETCHAR, 0, 0, 0)
 }
 
+/*
+**  @brief  call this function to shutdown
+**  @param  none
+**  @retval none
+*/
 pub fn shutdown() {
     sbi_call(SBI_SHUTDOWN, 0, 0, 0);
 }
 
+/*
+**  @brief  set a timer when running
+**  @param  stime_value: u64    time to be set
+**  @retval none
+*/
 pub fn set_timer(stime_value: u64) {
     #[cfg(target_pointer_width = "32")]
     sbi_call(SBI_SET_TIMER, stime_value as usize, (stime_value >> 32) as usize, 0);
@@ -32,22 +60,47 @@ pub fn set_timer(stime_value: u64) {
     sbi_call(SBI_SET_TIMER, stime_value as usize, 0, 0);
 }
 
+/*
+**  @brief  clear the ipi
+**  @param  none
+**  @retval none
+*/
 pub fn clear_ipi() {
     sbi_call(SBI_CLEAR_IPI, 0, 0, 0);
 }
 
+/*
+**  @brief  
+**  @param  
+**  @retval none
+*/
 pub fn send_ipi(hart_mask: *const usize) {
     sbi_call(SBI_SEND_IPI, hart_mask as usize, 0, 0);
 }
 
+/*
+**  @brief  
+**  @param  
+**  @retval none
+*/
 pub fn remote_fence_i(hart_mask: *const usize) {
     sbi_call(SBI_REMOTE_FENCE_I, hart_mask as usize, 0, 0);
 }
 
+/*
+**  @brief  
+**  @param  
+**  @retval none
+*/
 pub fn remote_sfence_vma(hart_mask: *const usize, _start: usize, _size: usize) {
     sbi_call(SBI_REMOTE_SFENCE_VMA, hart_mask as usize, 0, 0);
 }
 
+/*
+**  @brief  
+**  @param  
+**  @retval none
+*/
 pub fn remote_sfence_vma_asid(hart_mask: *const usize, _start: usize, _size: usize, _asid: usize) {
     sbi_call(SBI_REMOTE_SFENCE_VMA_ASID, hart_mask as usize, 0, 0);
 }