[RFC] wifi: iwlwifi: mei: Remove unused flexible-array member in struct iwl_sap_hdr?

[RFC] wifi: iwlwifi: mei: Remove unused flexible-array member in struct iwl_sap_hdr?

[Gustavo A. R. Silva]

Hi all,

At first sight, it seems that the flexible-array member `payload`
in the struct below it's not being used:

drivers/net/wireless/intel/iwlwifi/mei/sap.h:
298 /**
299  * struct iwl_sap_hdr - prefixes any SAP message
300  * @type: See &enum iwl_sap_msg.
301  * @len: The length of the message (header not included).
302  * @seq_num: For debug.
303  * @payload: The payload of the message.
304  */
305 struct iwl_sap_hdr {
306         __le16 type;
307         __le16 len;
308         __le32 seq_num;
309         u8 payload[];
310 };

If we remove it, we'd get rid of 14 of the following type of warnings:

drivers/net/wireless/intel/iwlwifi/mei/sap.h:318:28: warning: structure containing a flexible array member is not at the end of another structure 
[-Wflex-array-member-not-at-end]

Is there any case where this array is actually used that I might
be missing?

Thanks!
-Gustavo

Re: [RFC] wifi: iwlwifi: mei: Remove unused flexible-array member in struct iwl_sap_hdr?

[Johannes Berg]

On Mon, 2025-08-11 at 17:23 +0900, Gustavo A. R. Silva wrote:
> Hi all,
> 
> At first sight, it seems that the flexible-array member `payload`
> in the struct below it's not being used:
> 
> drivers/net/wireless/intel/iwlwifi/mei/sap.h:
> 298 /**
> 299  * struct iwl_sap_hdr - prefixes any SAP message
> 300  * @type: See &enum iwl_sap_msg.
> 301  * @len: The length of the message (header not included).
> 302  * @seq_num: For debug.
> 303  * @payload: The payload of the message.
> 304  */
> 305 struct iwl_sap_hdr {
> 306         __le16 type;
> 307         __le16 len;
> 308         __le32 seq_num;
> 309         u8 payload[];
> 310 };
> 
> If we remove it, we'd get rid of 14 of the following type of warnings:
> 
> drivers/net/wireless/intel/iwlwifi/mei/sap.h:318:28: warning: structure containing a flexible array member is not at the end of another structure 
> [-Wflex-array-member-not-at-end]
> 
> Is there any case where this array is actually used that I might
> be missing?

Check if it builds? But I don't see it used in our internal (and
possibly more recent) version of this either.

johannes

Re: [RFC] wifi: iwlwifi: mei: Remove unused flexible-array member in struct iwl_sap_hdr?

[Gustavo A. R. Silva]

On 25/08/25 10:20, Johannes Berg wrote:
> On Mon, 2025-08-11 at 17:23 +0900, Gustavo A. R. Silva wrote:
>> Hi all,
>>
>> At first sight, it seems that the flexible-array member `payload`
>> in the struct below it's not being used:
>>
>> drivers/net/wireless/intel/iwlwifi/mei/sap.h:
>> 298 /**
>> 299  * struct iwl_sap_hdr - prefixes any SAP message
>> 300  * @type: See &enum iwl_sap_msg.
>> 301  * @len: The length of the message (header not included).
>> 302  * @seq_num: For debug.
>> 303  * @payload: The payload of the message.
>> 304  */
>> 305 struct iwl_sap_hdr {
>> 306         __le16 type;
>> 307         __le16 len;
>> 308         __le32 seq_num;
>> 309         u8 payload[];
>> 310 };
>>
>> If we remove it, we'd get rid of 14 of the following type of warnings:
>>
>> drivers/net/wireless/intel/iwlwifi/mei/sap.h:318:28: warning: structure containing a flexible array member is not at the end of another structure
>> [-Wflex-array-member-not-at-end]
>>
>> Is there any case where this array is actually used that I might
>> be missing?
> 
> Check if it builds? But I don't see it used in our internal (and
> possibly more recent) version of this either.

It seems that the whole thing is actually broken, see commit 8997f5c8a627
("wifi: iwlwifi: Mark IWLMEI as broken").

However, nothing complains when built without that array. So, I've just
submitted a patch.

Thanks!
-Gustavo