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Message-ID: <0bee5aaaff4a4769d8f531552298feb2452f9026.camel@perches.com>
Subject: Re: [PATCH net] staging: rtl8188eu: use is_zero_ether_addr()
 instead of memcmp()
From:   Joe Perches <joe@perches.com>
To:     maowenan <maowenan@huawei.com>, Larry.Finger@lwfinger.net,
        gregkh@linuxfoundation.org, straube.linux@gmail.com,
        jananis37@gmail.com, devel@driverdev.osuosl.org,
        linux-kernel@vger.kernel.org, kernel-janitors@vger.kernel.org,
        davem@davemloft.net
Date:   Tue, 12 Mar 2019 00:06:04 -0700
In-Reply-To: <22e39cdc-6c66-f08a-f2b3-e2637e0b810b@huawei.com>
References: <20190309032600.98732-1-maowenan@huawei.com>
         <951c83d2-fa0d-11ed-96a9-cee620c9c096@huawei.com>
         <e192c19b35ba5a07ed6bea571546800cc3235282.camel@perches.com>
         <22e39cdc-6c66-f08a-f2b3-e2637e0b810b@huawei.com>
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On Tue, 2019-03-12 at 14:58 +0800, maowenan wrote:
> On 2019/3/12 14:35, Joe Perches wrote:
> > On Tue, 2019-03-12 at 14:29 +0800, maowenan wrote:
> > > ping...
> > > 
> > > On 2019/3/9 11:26, Mao Wenan wrote:
> > > > Using is_zero_ether_addr() instead of directly use
> > > > memcmp() to determine if the ethernet address is all
> > > > zeros.
> > []
> > > > diff --git a/drivers/staging/rtl8188eu/core/rtw_mlme.c b/drivers/staging/rtl8188eu/core/rtw_mlme.c
> > []
> > > > @@ -180,9 +180,8 @@ struct wlan_network *rtw_find_network(struct __queue *scanned_queue, u8 *addr)
> > > >  {
> > > >  	struct list_head *phead, *plist;
> > > >  	struct wlan_network *pnetwork = NULL;
> > > > -	u8 zero_addr[ETH_ALEN] = {0, 0, 0, 0, 0, 0};
> > > >  
> > > > -	if (!memcmp(zero_addr, addr, ETH_ALEN)) {
> > > > +	if (is_zero_ether_addr(addr)) {
> > 
> > How did you verify that addr is __aligned(2)?
> 
> /**
>  * is_zero_ether_addr - Determine if give Ethernet address is all zeros.
>  * @addr: Pointer to a six-byte array containing the Ethernet address
>  *
>  * Return true if the address is all zeroes.
>  */
> I think they are completely equivalent functions, no need to check addr is __aligned(2),
> because addr may be defined as unsigned char MacAddress[ETH_ALEN]; the length is 6.

Perhaps you are reading old documentation.
(though the "Please note:" line is from 2013)

include/linux/etherdevice.h-/**
include/linux/etherdevice.h- * is_zero_ether_addr - Determine if give Ethernet address is all zeros.
include/linux/etherdevice.h- * @addr: Pointer to a six-byte array containing the Ethernet address
include/linux/etherdevice.h- *
include/linux/etherdevice.h- * Return true if the address is all zeroes.
include/linux/etherdevice.h- *
include/linux/etherdevice.h- * Please note: addr must be aligned to u16.