spec: Add support for FWFT extension in SBI implementation

This commit introduces the necessary constants for Extension ID (EID) and Function ID (FID) associated with the Firmware Features Table (FWFT) extension, as per the RISC-V SBI specification. Documentation for these constants has also been updated to facilitate better understanding and usage.

Signed-off-by: Longbing Zheng <1211998648@qq.com>

sbi-spec/CHANGELOG.md

@@ -7,7 +7,9 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
 ## [Unreleased]
 
 ### Added
+
 - pmu: add config flags with bitflags in chapter 11
+- fwft: add support for FWFT extension in chapter 18
 
 ### Modified
 

sbi-spec/src/fwft.rs

@@ -0,0 +1,17 @@
+//! Chapter 18. Firmware Features Extension (EID #0x46574654 "FWFT").
+
+/// Extension ID for Firmware Features Extension.
+pub const EID_FWFT: usize = crate::eid_from_str("FWFT") as _;
+pub use fid::*;
+
+/// Declared in §18.3.
+mod fid {
+    /// Set the firmware function of the request based on Value and Flags parameters.
+    ///
+    /// Declared in §18.1.
+    pub const SET: usize = 0;
+    /// Return to the firmware function configuration value.
+    ///
+    /// Declared in §18.2.
+    pub const GET: usize = 1;
+}

sbi-spec/src/lib.rs

@@ -46,7 +46,8 @@ pub mod cppc;
 pub mod nacl;
 // §16
 pub mod sta;
-
+// §18
+pub mod fwft;
 /// Converts SBI EID from str.
 const fn eid_from_str(name: &str) -> i32 {
     match *name.as_bytes() {
@@ -335,4 +336,12 @@ mod tests {
         const_assert_eq!(0x535441, EID_STA);
         const_assert_eq!(0, SET_SHMEM);
     }
+    // §18
+    #[test]
+    fn test_fwft() {
+        use crate::fwft::*;
+        const_assert_eq!(0x46574654, EID_FWFT);
+        const_assert_eq!(0, SET);
+        const_assert_eq!(1, GET);
+    }
 }