linux-kernel - Re: [PATCH net] staging: rtl8188eu: use is_zero_ether

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Message-ID: <alpine.DEB.2.21.1903120813460.2728@hadrien>
Date:   Tue, 12 Mar 2019 08:14:37 +0100 (CET)
From:   Julia Lawall <julia.lawall@...6.fr>
To:     maowenan <maowenan@...wei.com>
cc:     Joe Perches <joe@...ches.com>, Larry.Finger@...inger.net,
        gregkh@...uxfoundation.org, straube.linux@...il.com,
        jananis37@...il.com, devel@...verdev.osuosl.org,
        linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org,
        davem@...emloft.net
Subject: Re: [PATCH net] staging: rtl8188eu: use is_zero_ether_addr() instead
 of memcmp()



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