netdev - Re: [PATCH 3/3] gianfar: fix endianness for hardware timestamp

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Date:	Wed, 24 Feb 2016 19:14:27 +0900
From:	YOSHIFUJI Hideaki <hideaki.yoshifuji@...aclelinux.com>
To:	Yangbo Lu <yangbo.lu@....com>,
	Richard Cochran <richardcochran@...il.com>
Cc:	hideaki.yoshifuji@...aclelinux.com,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	Claudiu Manoil <claudiu.manoil@...escale.com>
Subject: Re: [PATCH 3/3] gianfar: fix endianness for hardware timestamp

Hi,

Yangbo Lu wrote:
>> -----Original Message-----
>> From: Richard Cochran [mailto:richardcochran@...il.com]
>> Sent: Monday, February 22, 2016 4:48 PM
>> To: Yangbo Lu
>> Cc: netdev@...r.kernel.org; Claudiu Manoil
>> Subject: Re: [PATCH 3/3] gianfar: fix endianness for hardware timestamp
>>
>> On Mon, Feb 22, 2016 at 02:49:33PM +0800, Yangbo Lu wrote:
>>> @@ -2708,6 +2708,7 @@ static void gfar_clean_tx_ring(struct
>> gfar_priv_tx_q *tx_queue)
>>>  			struct skb_shared_hwtstamps shhwtstamps;
>>>  			u64 *ns = (u64 *)(((uintptr_t)skb->data + 0x10) &
>>>  					  ~0x7UL);
>>> +			*ns = be64_to_cpu(*ns);
>>>
>>>  			memset(&shhwtstamps, 0, sizeof(shhwtstamps));
>>>  			shhwtstamps.hwtstamp = ns_to_ktime(*ns);
>>
>> There is no point in modifying the buffer data in place.
>>
>> Instead, do this:
>>
>> 			memset(&shhwtstamps, 0, sizeof(shhwtstamps));
>> 			shhwtstamps.hwtstamp = ns_to_ktime(be64_to_cpu(*ns));
>>
>> or this:
>>
>> 			u64 ns, *ptr = (u64 *)(((uintptr_t)skb->data + 0x10) &
>> 					       ~0x7UL);
>> 			ns = be64_to_cpu(*ptr);
>>
>> 			memset(&shhwtstamps, 0, sizeof(shhwtstamps));
>> 			shhwtstamps.hwtstamp = ns_to_ktime(ns);
>>
> 
> [Lu Yangbo-B47093] I will modify codes according your suggestion.
> Thank you so much!

You may want to use PTR_ALIGN() and be64_to_cpup() here.

--yoshfuji

>  
>>> @@ -3037,6 +3038,7 @@ static void gfar_process_frame(struct net_device
>> *ndev, struct sk_buff *skb)
>>>  	if (priv->hwts_rx_en) {
>>>  		struct skb_shared_hwtstamps *shhwtstamps = skb_hwtstamps(skb);
>>>  		u64 *ns = (u64 *) skb->data;
>>> +		*ns = be64_to_cpu(*ns);
>>>
>>>  		memset(shhwtstamps, 0, sizeof(*shhwtstamps));
>>>  		shhwtstamps->hwtstamp = ns_to_ktime(*ns);
>>
>> Same here.
>>
>> Thanks,
>> Richard

-- 
Hideaki Yoshifuji <hideaki.yoshifuji@...aclelinux.com>
Technical Division, MIRACLE LINUX CORPORATION