Add an explicit mbedtls_mpi_core_montmul_working_limbs() function
Signed-off-by: Tom Cosgrove <tom.cosgrove@arm.com>
diff --git a/library/bignum_mod_raw.h b/library/bignum_mod_raw.h
index f9968ba..73eaf18 100644
--- a/library/bignum_mod_raw.h
+++ b/library/bignum_mod_raw.h
@@ -178,6 +178,10 @@
* \brief Returns the number of limbs of working memory required for
* a call to `mbedtls_mpi_mod_raw_inv_prime()`.
*
+ * \note This will always be at least
+ * `mbedtls_mpi_core_montmul_working_limbs(AN_limbs)`,
+ * i.e. sufficient for a call to `mbedtls_mpi_core_montmul()`.
+ *
* \param AN_limbs The number of limbs in the input `A` and the modulus `N`
* (they must be the same size) that will be given to
* `mbedtls_mpi_mod_raw_inv_prime()`.