linux-kernel - Re: [PATCH v2] ath6kl: replace one-element array with flexible-array member

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Date:   Mon, 7 Aug 2023 07:13:20 -0700
From:   Jeff Johnson <quic_jjohnson@...cinc.com>
To:     Greg KH <gregkh@...uxfoundation.org>, Kalle Valo <kvalo@...nel.org>
CC:     Atul Raut <rauji.raut@...il.com>,
        <linux-kernel-mentees@...ts.linuxfoundation.org>,
        <linux-wireless@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] ath6kl: replace one-element array with flexible-array
 member

On 8/4/2023 2:30 AM, Greg KH wrote:
> On Fri, Aug 04, 2023 at 10:10:37AM +0300, Kalle Valo wrote:
>> Greg KH <gregkh@...uxfoundation.org> writes:
>>
>>> On Thu, Aug 03, 2023 at 09:55:54PM -0700, Atul Raut wrote:
>>>
>>>> One-element arrays are no longer relevant, and their
>>>> place has been taken by flexible array members thus,
>>>> use a flexible-array member to replace the one-element
>>>> array in struct ath6kl_usb_ctrl_diag_cmd_write
>>>>
>>>> This fixes warnings such as:
>>>> ./drivers/net/wireless/ath/ath6kl/usb.c:109:8-12: WARNING use flexible-array member instead (https://www.kernel.org/doc/html/latest/process/deprecated.html#zero-length-and-one-element-arrays)
>>>>
>>>> Signed-off-by: Atul Raut <rauji.raut@...il.com>
>>>> ---
>>>>   drivers/net/wireless/ath/ath6kl/usb.c | 2 +-
>>>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>>>
>>>> diff --git a/drivers/net/wireless/ath/ath6kl/usb.c b/drivers/net/wireless/ath/ath6kl/usb.c
>>>> index 5220809841a6..c8ecc9e85897 100644
>>>> --- a/drivers/net/wireless/ath/ath6kl/usb.c
>>>> +++ b/drivers/net/wireless/ath/ath6kl/usb.c
>>>> @@ -106,7 +106,7 @@ struct ath6kl_usb_ctrl_diag_cmd_write {
>>>>   	__le32 cmd;
>>>>   	__le32 address;
>>>>   	__le32 value;
>>>> -	__le32 _pad[1];
>>>> +	__le32 _pad[];
>>>
>>> Are you sure this is actually a variable length array?
>>
>> It's not, it's just padding. We both told this in v1:
>>
>> https://patchwork.kernel.org/project/linux-wireless/patch/20230731012941.21875-1-rauji.raut@gmail.com/
> 
> Hey, I'm consistent, nice!  :)
> 
> But Atul, that's not good to ignore our review comments.  Usually that
> ends up meaning that everyone will then just ignore your submissions,
> generally a not-good resolution.
> 
> thanks,
> 
> greg k-h

Since the 'pad' field is never directly accessed, suggest the author 
respin this this to use simply:
	__le32 _pad;

That will prevent others from trying to "fix" this actual one-element 
array in the future.