firmware: arm_scmi: avoid returning uninialized data

From: Arnd Bergmann <[email protected]>

Clang notices that there is a code path through
scmi_powercap_notify_supported() that returns an
undefined value:

drivers/firmware/arm_scmi/powercap.c:821:11: error: variable 'supported' is used uninitialized whenever 'if' condition is false [-Werror,-Wsometimes-uninitialized]
821 | else if (evt_id == SCMI_EVENT_POWERCAP_MEASUREMENTS_CHANGED)

      |                  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/firmware/arm_scmi/powercap.c:824:9: note: uninitialized use occurs here
  824 |         return supported;
      |                ^~~~~~~~~
drivers/firmware/arm_scmi/powercap.c:821:7: note: remove the 'if' if its condition is always true
  821 |         else if (evt_id == SCMI_EVENT_POWERCAP_MEASUREMENTS_CHANGED)
      |              ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  822 |                 supported = dom_info->notify_powercap_measurement_change;

drivers/firmware/arm_scmi/powercap.c:811:16: note: initialize the variable 'supported' to silence this warning
811 | bool supported;
| ^

Return 'false' here, which is probably what was intended.

Fixes c92a75fe84ce ("firmware: arm_scmi: Implement Powercap .is_notify_supported callback")

Signed-off-by Arnd Bergmann <[email protected]>

---
 drivers/firmware/arm_scmi/powercap.c | 2 ++
 1 file changed, 2 insertions(+)

drivers/firmware/arm_scmi/powercap.c +2 -0

index aae91f47303e..8ee3be8776b0 100644
@@ -820,6 +820,8 @@ scmi_powercap_notify_supported(const struct scmi_protocol_handle *ph,
 		supported = dom_info->notify_powercap_cap_change;
 	else if (evt_id == SCMI_EVENT_POWERCAP_MEASUREMENTS_CHANGED)
 		supported = dom_info->notify_powercap_measurement_change;
+	else
+		supported = false;
 
 	return supported;
 }

Signature · 1 line

2.39.2

Quoted 6 lines · Arnd Bergmann

From: Arnd Bergmann <[email protected]>

Clang notices that there is a code path through
scmi_powercap_notify_supported() that returns an
undefined value:

thanks for looking at this, this series that I've just posted is still to be reviewd at all, so I would expect issues :D...BUT in this case I dont think that the clang report is valid since, inside the culprit function scmi_powercap_notify_supported(), a few lines before the reported usage of unitialized data there is a check (@line 816) on the 'bounds' of evt_id itself

	if (evt_id >= ARRAY_SIZE(evt_2_cmd) || src_id >= pi->num_domains)
		return false;

so basically the mentioned if/else WILL be evaluated in some of its branches for sure and supported wont be uninitialized.

Indeed, I removed from here (and from all the series) the explicit initialization at definition time right before posting the series.

Having saidm that...maybe it is just brain-dead this approach of mine since it is able to fool clang & friends...I would add bACK an explicit initialization of supported all across this series in V2, if this sounds good to you.