Re: [PATCH v2] kconfig: Add transitional symbol attribute for migration support

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On 01/09/2025 18:56, Kees Cook wrote:
@@ -459,13 +462,15 @@ void sym_calc_value(struct symbol *sym)
   			sym_calc_choice(choice_menu);
   			newval.tri = sym->curr.tri;
   		} else {
-			if (sym->visible != no) {
+			if (sym->usable) {
   				/* if the symbol is visible use the user value
   				 * if available, otherwise try the default value
   				 */
   				if (sym_has_value(sym)) {
+					tristate value = sym->transitional ?
+						sym->def[S_DEF_USER].tri : sym->visible;
   					newval.tri = EXPR_AND(sym->def[S_DEF_USER].tri,
-							      sym->visible);
+							      value);
This looks a bit odd to me. Just thinking out loud: your new logic is
there to be able to use a value even though it's not visible. In the
case where it's transitional you use the .config value instead of the
condition that makes it visible.

Could you simply change sym_calc_visibility() instead to always return
'yes' when the symbol is transitional? Wouldn't that simplify everything
in sym_calc_value()?
It's a tristate, so "m" is also possible besides "y". (sym->visible is
also a tristate. 🙂

That would be fine, right?

We'd pass the if (sym->visible != no) check... we'd do the

newval.tri = EXPR_AND(sym->def[S_DEF_USER].tri, sym->visible);

EXPR_AND() is basically min() (with n=0, m=1, y=2), so effectively it
would end up doing

newval.tri = min(sym->def[S_DEF_USER].tri, 2);

which is the same as

newval.tri = sym->def[S_DEF_USER].tri;

That's what your code is currently doing too, but in a much more
roundabout way.


Vegard




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