linux-kernel - Re: [PATCH] drm/amdkfd: Replace one-element array with flexible-array member

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Message-ID: <0eeaa0b7-7ae6-c244-cfcd-86333d8f9b8b@amd.com>
Date:   Fri, 18 Feb 2022 17:29:27 +0100
From:   Christian König <christian.koenig@....com>
To:     Felix Kuehling <felix.kuehling@....com>, cgel.zte@...il.com
Cc:     alexander.deucher@....com, Xinhui.Pan@....com, airlied@...ux.ie,
        daniel@...ll.ch, amd-gfx@...ts.freedesktop.org,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        Changcheng Deng <deng.changcheng@....com.cn>,
        Zeal Robot <zealci@....com.cn>
Subject: Re: [PATCH] drm/amdkfd: Replace one-element array with flexible-array
 member

Well in that case somebody could argue that we should probably remove 
the structure altogether.

Regards,
Christian.

Am 18.02.22 um 17:15 schrieb Felix Kuehling:
> It looks like this structure isn't being used at all. So I'm OK with 
> this change, in case we ever use it in the future.
>
> Regards,
>   Felix
>
>
> Am 2022-02-18 um 02:47 schrieb Christian König:
>> Felix need to comment as well, but I don't think that this will work 
>> that easily.
>>
>> By changing the entry from 1 to 0 your are also changing the size of 
>> the structure.
>>
>> Regards,
>> Christian.
>>
>> Am 18.02.22 um 04:09 schrieb cgel.zte@...il.com:
>>> From: Changcheng Deng <deng.changcheng@....com.cn>
>>>
>>> There is a regular need in the kernel to provide a way to declare 
>>> having
>>> a dynamically sized set of trailing elements in a structure. Kernel 
>>> code
>>> should always use "flexible array members" for these cases. The older
>>> style of one-element or zero-length arrays should no longer be used.
>>> Reference:
>>> https://www.kernel.org/doc/html/latest/process/deprecated.html#zero-length-and-one-element-arrays 
>>>
>>>
>>> Reported-by: Zeal Robot <zealci@....com.cn>
>>> Signed-off-by: Changcheng Deng <deng.changcheng@....com.cn>
>>> ---
>>>   drivers/gpu/drm/amd/amdkfd/kfd_crat.h | 2 +-
>>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_crat.h 
>>> b/drivers/gpu/drm/amd/amdkfd/kfd_crat.h
>>> index 482ba84a728d..d7c38fbc533e 100644
>>> --- a/drivers/gpu/drm/amd/amdkfd/kfd_crat.h
>>> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_crat.h
>>> @@ -310,7 +310,7 @@ struct cdit_header {
>>>       uint32_t    creator_revision;
>>>       uint32_t    total_entries;
>>>       uint16_t    num_domains;
>>> -    uint8_t        entry[1];
>>> +    uint8_t        entry[];
>>>   };
>>>     #pragma pack()
>>