> On 7 Oct 2022, at 20:04, Devendra Tewari <devendra.tewari@xxxxxxxxx> wrote:
>
>
>
>> No dia 7 de out. de 2022, às 18:58, Kieran Bingham <kieran.bingham@xxxxxxxxxxxxxxxx> escreveu:
>>
>> Hi Devendra,
>>
>> Quoting Devendra Tewari (2022-04-22 20:20:31)
>>> Fixes clang warning: field within 'v4l2_ext_control' is less than
>>
>> Can you detail which version of clang this occurs with? Have you tried
>> more than one version?
>>
>
> This started happening with version 14.0.1 and I continue to see it with version 15.
>
>>
>>> 'v4l2_ext_control::(anonymous union
>>>
>>> Signed-off-by: Devendra Tewari <devendra.tewari@xxxxxxxxx>
>>> ---
>>> include/uapi/linux/videodev2.h | 2 +-
>>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
>>> index 3768a0a80830..767c52c722cd 100644
>>> --- a/include/uapi/linux/videodev2.h
>>> +++ b/include/uapi/linux/videodev2.h
>>> @@ -1765,7 +1765,7 @@ struct v4l2_ext_control {
>>> struct v4l2_ctrl_vp9_compressed_hdr __user *p_vp9_compressed_hdr_probs;
>>> struct v4l2_ctrl_vp9_frame __user *p_vp9_frame;
>>> void __user *ptr;
>>> - };
>>> + } __attribute__ ((packed));
>>
>> This is a curious fix. It's applying a packed attribute to the union,
>> which I presume means that it's then applying the packed attribute to
>> any item in the union.
>>
>> The items are all either: __s32, __s64, values - or pointers.
>>
>> While applying this attribute here may fix the compiler warning, I'm not
>> sure it's clear why this is required. This file also has other
>> locations where a union inside a packed struct is not marked as packed.
>> Should all unions be marked with the attribute?
>
> Interesting - I need to look deeper into packed.
The only explanation I can think of is that this may be the only instance where a union inside a packed struct has other structs that are not packed.
>
>> Is there any more context from the compiler warning beyond what is
>> reported above?
>
> I'll post a more detailed log asap.
>
>>
>> --
>> Kieran
>>
>>
>>> } __attribute__ ((packed));
>>>
>>> struct v4l2_ext_controls {
>>> --
>>> 2.25.1
>>>
> Thanks,
> Devendra
Resending because mail daemon rejected rich text message.
Thanks,
Devendra
