firmware: arm_ffa: Explicitly cast return value from NOTIFICATION_INFO_GET

The return value ret.a2 is of type unsigned long and FFA_RET_NO_DATA is
a negative value.

Since the return value from the firmware can be just 32-bit even on
64-bit systems as FFA specification mentions it as int32 error code in
w0 register, explicitly casting to s32 ensures correct sign interpretation
when comparing against a signed error code FFA_RET_NO_DATA.

Without casting, comparison between unsigned long and a negative
constant could lead to unintended results due to type promotions.

Fixes: 3522be48d82b ("firmware: arm_ffa: Implement the NOTIFICATION_INFO_GET interface")
Reported-by: Andrei Homescu <ahomescu@google.com>
Message-Id: <20250221095633.506678-2-sudeep.holla@arm.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>

diff --git a/drivers/firmware/arm_ffa/driver.c b/drivers/firmware/arm_ffa/driver.c
index 7c288ae74f97c34e616edaef4e43d8e6562493d9..37305f37132cecaf19ee2ab717492df0f2456557 100644 (file)
--- a/drivers/firmware/arm_ffa/driver.c
+++ b/drivers/firmware/arm_ffa/driver.c
@@ -976,7 +976,7 @@ static void ffa_notification_info_get(void)
                          }, &ret);
 
                if (ret.a0 != FFA_FN_NATIVE(SUCCESS) && ret.a0 != FFA_SUCCESS) {
-                       if (ret.a2 != FFA_RET_NO_DATA)
+                       if ((s32)ret.a2 != FFA_RET_NO_DATA)
                                pr_err("Notification Info fetch failed: 0x%lx (0x%lx)",
                                       ret.a0, ret.a2);
                        return;