diff --git a/docs/proposed/psa-driver-interface.md b/docs/proposed/psa-driver-interface.md
index 18b15ed7f..a0e16e1f3 100644
--- a/docs/proposed/psa-driver-interface.md
+++ b/docs/proposed/psa-driver-interface.md
@@ -840,6 +840,19 @@ psa_set_key_lifetime(&attributes, PSA_KEY_LIFETIME_FROM_PERSISTENCE_AND_LOCATION
 
 ## Open questions
 
+### Value representation
+
+#### Integers
+
+It would be better if there was a uniform requirement on integer values. Do they have to be JSON integers? C preprocessor integers (which could be e.g. a macro defined in some header file)? C compile-time constants (allowing `sizeof`)?
+
+This choice is partly driven by the use of the values, so they might not be uniform. Note that if the value can be zero and it's plausible that the core would want to statically allocate an array of the given size, the core needs to know whether the value is 0 so that it could use code like
+```
+#if ACME_FOO_SIZE != 0
+    uint8_t foo[ACME_FOO_SIZE];
+#endif
+```
+
 ### Driver declarations
 
 #### Declaring driver entry points