Document that MBEDTLS_PSA_CRYPTO_SPM needs crypto_spe.h
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/include/mbedtls/mbedtls_config.h b/include/mbedtls/mbedtls_config.h
index e9354da..1c541ca 100644
--- a/include/mbedtls/mbedtls_config.h
+++ b/include/mbedtls/mbedtls_config.h
@@ -1410,6 +1410,13 @@
* NSPE (Non-Secure Process Environment) and an SPE (Secure Process
* Environment).
*
+ * If you enable this option, your build environment must include a header
+ * file `"crypto_spe.h"` (either in the `psa` subdirectory of the Mbed TLS
+ * header files, or in another directory on the compiler's include search
+ * path). Alternatively, your platform may customize the header
+ * `psa/crypto_platform.h`, in which case it can skip or replace the
+ * inclusion of `"crypto_spe.h"`.
+ *
* Module: library/psa_crypto.c
* Requires: MBEDTLS_PSA_CRYPTO_C
*