Re: [PATCH] Bluetooth: btusb: Use DECLARE_FLEX_ARRAY() for memdump segment data

[Zijun Hu]

On 11/8/2026 12:20 PM, Hex Lindqvist wrote:
> struct qhci_vse_memdump declares segdata as a zero-length array in a
> union. Zero-length arrays are deprecated [1], so use DECLARE_FLEX_ARRAY()
> instead.
> 
> No functional change: segdata is only used with offsetof(). With debug
> info stripped, btusb.o is byte-for-byte identical before and after,
> built with GCC 16 and Clang 21 on x86_64 and GCC 16 on arm64, with
> UBSAN_BOUNDS and FORTIFY_SOURCE enabled.
> 
> An AI assistant helped find and check this change and drafted this
> message.
> 
> Link: https://docs.kernel.org/process/deprecated.html#zero-length-and-one-element-arrays [1]
> Signed-off-by: Hex Lindqvist <hex@xxxxxxxxxxxxx>
> ---
>  drivers/bluetooth/btusb_qcom.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/bluetooth/btusb_qcom.c b/drivers/bluetooth/btusb_qcom.c
> index cc4cfcde2afa..97be9078e045 100644
> --- a/drivers/bluetooth/btusb_qcom.c
> +++ b/drivers/bluetooth/btusb_qcom.c
> @@ -533,7 +533,7 @@ struct qhci_vse_memdump {
>  	__le16 seqno;
>  	u8     subsys;
>  	union {
> -		u8 segdata[0];
> +		DECLARE_FLEX_ARRAY(u8, segdata);
>  		struct {
>  			__le32 dump_size;
>  			u8 first_segdata[];

NAK. Please keep this as-is. since:

1) segdata[0] is a familiar GNU C idiom and, since it is only used as an offsetof() anchor, is more straightforward than the
  DECLARE_FLEX_ARRAY() expansion.

2) I guess this kind of isolated cleanup may not be welcome.As noted in Documentation/process/maintainer-netdev.rst, simple cleanups outside
   the context of other work are discouraged