[PATCH][next] iio: proximity: cros_ec_mkbp_proximity: Avoid -Wflex-array-member-not-at-end warning

[PATCH][next] iio: proximity: cros_ec_mkbp_proximity: Avoid -Wflex-array-member-not-at-end warning

[Gustavo A. R. Silva]

-Wflex-array-member-not-at-end was introduced in GCC-14, and we are
getting ready to enable it, globally.

Use the `DEFINE_RAW_FLEX()` helper for an on-stack definition of
a flexible structure where the size of the flexible-array member
is known at compile-time, and refactor the rest of the code,
accordingly.

So, with these changes, fix the following warning:

drivers/iio/proximity/cros_ec_mkbp_proximity.c:63:40: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]

Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
---

This looks pretty much like the following patch for RTC:

https://lore.kernel.org/linux-hardening/Z9PpPg06OK8ghNvm@kspp/

Thanks

 drivers/iio/proximity/cros_ec_mkbp_proximity.c | 14 ++++----------
 1 file changed, 4 insertions(+), 10 deletions(-)

diff --git a/drivers/iio/proximity/cros_ec_mkbp_proximity.c b/drivers/iio/proximity/cros_ec_mkbp_proximity.c
index 667369be0555..4fe3d84e2729 100644
--- a/drivers/iio/proximity/cros_ec_mkbp_proximity.c
+++ b/drivers/iio/proximity/cros_ec_mkbp_proximity.c
@@ -59,16 +59,10 @@ static int cros_ec_mkbp_proximity_parse_state(const void *data)
 static int cros_ec_mkbp_proximity_query(struct cros_ec_device *ec_dev,
 					int *state)
 {
-	struct {
-		struct cros_ec_command msg;
-		union {
-			struct ec_params_mkbp_info params;
-			u32 switches;
-		};
-	} __packed buf = { };
-	struct ec_params_mkbp_info *params = &buf.params;
-	struct cros_ec_command *msg = &buf.msg;
-	u32 *switches = &buf.switches;
+	DEFINE_RAW_FLEX(struct cros_ec_command, buf, data, sizeof(u32));
+	struct ec_params_mkbp_info *params = (struct ec_params_mkbp_info *)buf->data;
+	struct cros_ec_command *msg = buf;
+	u32 *switches = (u32 *)buf->data;
 	size_t insize = sizeof(*switches);
 	int ret;
 
-- 
2.43.0

Re: [PATCH][next] iio: proximity: cros_ec_mkbp_proximity: Avoid -Wflex-array-member-not-at-end warning

[Tzung-Bi Shih]

On Mon, Mar 17, 2025 at 11:25:40AM +1030, Gustavo A. R. Silva wrote:
>  static int cros_ec_mkbp_proximity_query(struct cros_ec_device *ec_dev,
>  					int *state)
>  {
> -	struct {
> -		struct cros_ec_command msg;
> -		union {
> -			struct ec_params_mkbp_info params;
> -			u32 switches;
> -		};
> -	} __packed buf = { };
> -	struct ec_params_mkbp_info *params = &buf.params;
> -	struct cros_ec_command *msg = &buf.msg;
> -	u32 *switches = &buf.switches;
> +	DEFINE_RAW_FLEX(struct cros_ec_command, buf, data, sizeof(u32));

max(sizeof(struct ec_params_mkbp_info), sizeof(u32))?

Re: [PATCH][next] iio: proximity: cros_ec_mkbp_proximity: Avoid -Wflex-array-member-not-at-end warning

[Jonathan Cameron]

On Mon, 17 Mar 2025 01:36:58 +0000
Tzung-Bi Shih <tzungbi@kernel.org> wrote:

> On Mon, Mar 17, 2025 at 11:25:40AM +1030, Gustavo A. R. Silva wrote:
> >  static int cros_ec_mkbp_proximity_query(struct cros_ec_device *ec_dev,
> >  					int *state)
> >  {
> > -	struct {
> > -		struct cros_ec_command msg;
> > -		union {
> > -			struct ec_params_mkbp_info params;
> > -			u32 switches;
> > -		};
> > -	} __packed buf = { };
> > -	struct ec_params_mkbp_info *params = &buf.params;
> > -	struct cros_ec_command *msg = &buf.msg;
> > -	u32 *switches = &buf.switches;
> > +	DEFINE_RAW_FLEX(struct cros_ec_command, buf, data, sizeof(u32));  
> 
> max(sizeof(struct ec_params_mkbp_info), sizeof(u32))?

If not (I assume same reason as previous case), then maybe an assert
that sizeof(struct ec_params_mkbp_info) <= sizeof(u32)?