linux-kernel - Re: [PATCH 3/5] staging: rtl8188eu: use is_multicast_ether_addr in rtw

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Message-ID: <6da72965-8228-46bf-9c5b-981d761836bb@gmail.com>
Date:   Thu, 9 Aug 2018 20:03:18 +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,
        Alexander Duyck <alexander.h.duyck@...hat.com>,
        "David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH 3/5] staging: rtl8188eu: use is_multicast_ether_addr in
 rtw_xmit.c

On 8/9/18 7:51 PM, Joe Perches wrote:
> On Thu, 2018-08-09 at 19:42 +0200, Michael Straube wrote:
>> On 8/9/18 7:13 PM, Joe Perches wrote:
>>> On Thu, 2018-08-09 at 19:01 +0200, Michael Straube wrote:
>>>> Use is_multicast_ether_addr instead of custom IS_MCAST in
>>>> core/rtw_xmit.c.
>>>
>>> Have you verified that all accesses are __aligned(2) ?
>>>
>>> If so, please state that in the patch description.
>>>
>>>> diff --git a/drivers/staging/rtl8188eu/core/rtw_xmit.c b/drivers/staging/rtl8188eu/core/rtw_xmit.c
>>>
>>> []
>>>> @@ -460,10 +460,10 @@ static s32 update_attrib(struct adapter *padapter, struct sk_buff *pkt, struct p
>>>>    	if ((pattrib->ether_type == ETH_P_ARP) || (pattrib->ether_type == ETH_P_PAE) || (pattrib->dhcp_pkt == 1))
>>>>    		rtw_lps_ctrl_wk_cmd(padapter, LPS_CTRL_SPECIAL_PACKET, 1);
>>>>    
>>>> -	bmcast = IS_MCAST(pattrib->ra);
>>>> +	mcast = is_multicast_ether_addr(pattrib->ra);
>>>
>>> i.e.:  is pattrib->ra __aligned(2) ?
>>>
>>> etc...
>>>
>>
>> Hi Joe,
>>
>> I looked at the function comment for is_multicast_ether_addr in etherdevice.h.
>> There is not mentioned that __aligned(2) is required. If it is, I will check.
>>
>> So, is it required although it's not mentioned for is_multicast_ether_addr?
> 
> Well, it wasn't required initially, but
> 
> commit d54385ce68cd18ab002b46f61246ad197cec92de
> Author: Alexander Duyck <alexander.h.duyck@...hat.com>
> Date:   Thu Apr 30 14:53:54 2015 -0700
> 
>      etherdev: Process is_multicast_ether_addr at same size as other operations
>      
>      This change makes it so that we process the address in
>      is_multicast_ether_addr at the same size as the other calls.  This allows
>      us to avoid duplicate reads when used with other calls such as
>      is_zero_ether_addr or eth_addr_copy.  In addition I have added a 64 bit
>      version of the function so in eth_type_trans we can process the destination
>      address as a 64 bit value throughout.
>      
>      Signed-off-by: Alexander Duyck <alexander.h.duyck@...hat.com>
>      Signed-off-by: David S. Miller <davem@...emloft.net>
> 
> changed it without adding a note in the kernel-doc.
> 
> So this is likely appropriate to avoid unaligned access traps:
> ---
>   include/linux/etherdevice.h | 2 ++
>   1 file changed, 2 insertions(+)
> 
> diff --git a/include/linux/etherdevice.h b/include/linux/etherdevice.h
> index 572e11bb8696..0f7086b4836a 100644
> --- a/include/linux/etherdevice.h
> +++ b/include/linux/etherdevice.h
> @@ -115,6 +115,8 @@ static inline bool is_zero_ether_addr(const u8 *addr)
>    *
>    * Return true if the address is a multicast address.
>    * By definition the broadcast address is also a multicast address.
> + *
> + * Please note: addr must be aligned to u16.
>    */
>   static inline bool is_multicast_ether_addr(const u8 *addr)
>   {
> 

Ok, then I will check and resend the series.
Thanks again.