Improve the interface to access CSRs in extensions.

1 files changed, 20 insertions, 0 deletions

diff --git a/model/riscv_csr_ext.sail b/model/riscv_csr_ext.sail
new file mode 100644
index 0000000..ea4f065
--- /dev/null
+++ b/model/riscv_csr_ext.sail
@@ -0,0 +1,20 @@
+/* Extensions may want to add additional CSR registers to the CSR address map.
+ * These functions support access to such registers.
+ *
+ * The default implementation provides access to the CSRs added by the 'N'
+ * extension.
+ */
+
+/* returns whether a CSR is defined and accessible at a given address
+ * and privilege
+ */
+function ext_is_CSR_defined(csr : csreg, p : Privilege) -> bool =
+  is_NExt_CSR_defined(csr, p)   // 'N' extension
+
+/* returns the value of the CSR if it is defined */
+function ext_read_CSR(csr : csreg) -> option(xlenbits) =
+  read_NExt_CSR(csr)
+
+/* returns false if the CSR is not defined or if the write is unsuccessful */
+function ext_write_CSR(csr : csreg, value : xlenbits) -> bool =
+  write_NExt_CSR(csr, value)