Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Tue, 12 Mar 2019 08:14:37 +0100 (CET)
From:   Julia Lawall <julia.lawall@lip6.fr>
To:     maowenan <maowenan@huawei.com>
cc:     Joe Perches <joe@perches.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
Subject: Re: [PATCH net] staging: rtl8188eu: use is_zero_ether_addr() instead
 of memcmp()
In-Reply-To: <22e39cdc-6c66-f08a-f2b3-e2637e0b810b@huawei.com>
Message-ID: <alpine.DEB.2.21.1903120813460.2728@hadrien>
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>
User-Agent: Alpine 2.21 (DEB 202 2017-01-01)
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk


On Tue, 12 Mar 2019, 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 confusing with eth_zero_addr, which is just a memset and
has no alignment requirements.

julia