netdev - Re: [PATCH net-next 5/7] s390/qeth: improve endianness handling

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Date:   Tue, 11 Apr 2017 12:20:28 +0200
From:   Ursula Braun <ubraun@...ux.vnet.ibm.com>
To:     David Laight <David.Laight@...LAB.COM>,
        "davem@...emloft.net" <davem@...emloft.net>
Cc:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-s390@...r.kernel.org" <linux-s390@...r.kernel.org>,
        "jwi@...ux.vnet.ibm.com" <jwi@...ux.vnet.ibm.com>,
        "schwidefsky@...ibm.com" <schwidefsky@...ibm.com>,
        "heiko.carstens@...ibm.com" <heiko.carstens@...ibm.com>,
        "raspl@...ux.vnet.ibm.com" <raspl@...ux.vnet.ibm.com>,
        Hans Wippel <hwippel@...ux.vnet.ibm.com>
Subject: Re: [PATCH net-next 5/7] s390/qeth: improve endianness handling



On 04/10/2017 05:22 PM, David Laight wrote:
> From: Ursula Braun
>> Sent: 07 April 2017 13:33
>> On 04/07/2017 01:25 PM, David Laight wrote:
>>> From: Ursula Braun
>>>> Sent: 05 April 2017 09:40
>>>> From: Hans Wippel <hwippel@...ux.vnet.ibm.com>
>>>>
>>>> Avoid endianness warnings reported by sparse by (1) using endianness
>>>> conversions for assigning and using network packet fields, and (2)
>>>> removing unnecessary endianness conversions from qeth_l3_rebuild_skb. No
>>>> functional changes.
>>>>
>>>> Signed-off-by: Hans Wippel <hwippel@...ux.vnet.ibm.com>
>>>> Signed-off-by: Ursula Braun <ubraun@...ux.vnet.ibm.com>
>>>> ---
>>>>  drivers/s390/net/qeth_core.h      |  4 ++--
>>>>  drivers/s390/net/qeth_core_main.c | 11 +++++-----
>>>>  drivers/s390/net/qeth_l3_main.c   | 46 +++++++++++++++++++--------------------
>>>>  drivers/s390/net/qeth_l3_sys.c    |  4 ++--
>>>>  4 files changed, 33 insertions(+), 32 deletions(-)
>>>>
>>>> diff --git a/drivers/s390/net/qeth_core.h b/drivers/s390/net/qeth_core.h
>>>> index 22aa2cd..6764ab9 100644
>>>> --- a/drivers/s390/net/qeth_core.h
>>>> +++ b/drivers/s390/net/qeth_core.h
>>>> @@ -844,9 +844,9 @@ static inline int qeth_get_ip_version(struct sk_buff *skb)
>>>>  {
>>>>  	__be16 *p = &((struct ethhdr *)skb->data)->h_proto;
>>>>
>>>> -	if (*p == ETH_P_8021Q)
>>>> +	if (be16_to_cpu(*p) == ETH_P_8021Q)
>>>>  		p += 2;
>>>> -	switch (*p) {
>>>> +	switch (be16_to_cpu(*p)) {
>>>>  	case ETH_P_IPV6:
>>>
>>> These are definitely 'functional changes' on LE systems.
>> s390 is Big Endian; thus the change is basicly a NOP.
> 
>> The only purpose of this kind of patches is getting rid
>> of sparse warnings with our code.
> 
> Then say so in the commit message....
Understood, in future we will try to improve our commit message.
> 
> What you are really doing is fixing the code in case anyone tries
> to use it on a LE system.
> 
> 	David
>