linux-kernel - Re: [PATCH 8/8] staging: rtl8188eu: use is_broadcast_ether

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Message-ID: <d4c695a5-39fe-4f96-49fb-58e574ec8cb2@gmail.com>
Date:   Sun, 29 Jul 2018 20:51:56 +0200
From:   Michael Straube <straube.linux@...il.com>
To:     Joe Perches <joe@...ches.com>, gregkh@...uxfoundation.org
Cc:     devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 8/8] staging: rtl8188eu: use is_broadcast_ether_addr

On 07/29/18 20:21, Michael Straube wrote:
> On 07/29/18 19:59, Joe Perches wrote:
>> On Sun, 2018-07-29 at 19:42 +0200, Michael Straube wrote:
>>> On 07/29/18 19:21, Joe Perches wrote:
>>>> On Sun, 2018-07-29 at 19:08 +0200, Michael Straube wrote:
>>>>> Use is_broadcast_ether_addr instead of checking each byte of the
>>>>> address array for 0xff. Shortens the code and improves readability.
>>>>
>>>> You should show in the commit log that sta_addr is __aligned(2)
>>>> as required by is_broadcast_ether_addr, otherwise you could be
>>>> introducing runtime alignment defects.
>>>>
>>>
>>> Ok, sta_addr is used from following structs.
>>>
>>> struct ieee_param {
>>>           u32 cmd;
>>>           u8 sta_addr[ETH_ALEN];
>>>           union {
>>>           ...
>>>           ...
>>>           }; u
>>> };
>>>
>>> struct ieee_param_ex {
>>>     u32 cmd;
>>>     u8 sta_addr[ETH_ALEN];
>>>     u8 data[0];
>>> };
>>>
>>> Well, looking at it now, I'm not sure about the alignment anymore
>>> in the struct that contains the union. Is sta_addr in the first
>>> struct __aligned(2)?
>>>
>>> Should I include the snippets in the commit message, or is just
>>> writing that sta_addr is __aligned(2) enough? (if it is in the
>>> first case...)
>>
>> It's enough to just state that the uses are properly aligned
>> as long as you looked and understand that it's required.
>>
> 
> Ok, thank you.
> 
> I looked at it and understand that it's required.
> But, as mentioned, at second look I'm not sure about the union.
> 
> I guess I need to read a little more about the alignment of unions.

For now I will resend the series without this patch.
I don't feel comfortable with sending something I don't fully understand, yet.

Michael