From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from szxga03-in.huawei.com (szxga03-in.huawei.com [45.249.212.189]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E499372 for ; Wed, 9 Jun 2021 03:01:23 +0000 (UTC) Received: from dggemv703-chm.china.huawei.com (unknown [172.30.72.55]) by szxga03-in.huawei.com (SkyGuard) with ESMTP id 4G0Bbr6pQ0z6vPw; Wed, 9 Jun 2021 10:57:28 +0800 (CST) Received: from dggpemm500009.china.huawei.com (7.185.36.225) by dggemv703-chm.china.huawei.com (10.3.19.46) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2176.2; Wed, 9 Jun 2021 11:01:18 +0800 Received: from [10.174.179.24] (10.174.179.24) by dggpemm500009.china.huawei.com (7.185.36.225) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2176.2; Wed, 9 Jun 2021 11:01:18 +0800 Subject: Re: [PATCH -next 2/2] staging: r8188eu: use eth_broadcast_addr() to assign broadcast address To: Joe Perches , Greg Kroah-Hartman References: <20210608141620.525521-1-liushixin2@huawei.com> CC: , From: Liu Shixin Message-ID: <4773dedc-dd39-ce1c-f7a6-58a93799fd92@huawei.com> Date: Wed, 9 Jun 2021 11:01:18 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.7.1 X-Mailing-List: linux-staging@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.179.24] X-ClientProxiedBy: dggems701-chm.china.huawei.com (10.3.19.178) To dggpemm500009.china.huawei.com (7.185.36.225) X-CFilter-Loop: Reflected On 2021/6/9 1:34, Joe Perches wrote: > On Tue, 2021-06-08 at 19:01 +0200, Greg Kroah-Hartman wrote: >> On Tue, Jun 08, 2021 at 09:45:49AM -0700, Joe Perches wrote: >>> On Tue, 2021-06-08 at 16:12 +0200, Greg Kroah-Hartman wrote: >>>> On Tue, Jun 08, 2021 at 10:16:20PM +0800, Liu Shixin wrote: >>>>> Use eth_broadcast_addr() to assign broadcast address. >>>> That says what you do, but not _why_ you are doing this? >>>> >>>> Why make this change? What benifit does it provide? >>> The commit message is clear and concise as using available kernel >>> mechanisms is better than homegrown or duplicative ones. >>> >>> Are you asking merely becuse Liu Shixin hasn't had many staging >>> commits? >> I'm asking because this changelog text does not explain why this is >> needed at all and needs to be changed to do so. > IYO. > > IMO it's obvious and fine as is and you are asking for overly > fine-grained analyses in commit messages. > > The subject is clear though the commit message is merely duplicative. > > It _could_ show the reduction in object size for some versions of gcc. > > $ size drivers/staging/rtl8188eu/core/rtw_mlme_ext.o* > text data bss dec hex filename > 53259 372 2430 56061 dafd drivers/staging/rtl8188eu/core/rtw_mlme_ext.o.gcc6.new > 53355 372 2430 56157 db5d drivers/staging/rtl8188eu/core/rtw_mlme_ext.o.gcc6.old > 54673 372 2430 57475 e083 drivers/staging/rtl8188eu/core/rtw_mlme_ext.o.gcc10.new > 54673 372 2430 57475 e083 drivers/staging/rtl8188eu/core/rtw_mlme_ext.o.gcc10.old > > It _could_ describe how the kernel mechanisms depend on a minimum > alignment of __aligned(2) in the tested address and also show that > the address is properly minimum aligned. > > struct ieee80211_hdr { > __le16 frame_control; > __le16 duration_id; > u8 addr1[ETH_ALEN]; > u8 addr2[ETH_ALEN]; > u8 addr3[ETH_ALEN]; > __le16 seq_ctrl; > u8 addr4[ETH_ALEN]; > } __packed __aligned(2); > [...] > struct ieee80211_hdr *pwlanhdr; > [...] > - ether_addr_copy(pwlanhdr->addr1, bc_addr); > + eth_broadcast_addr(pwlanhdr->addr1); > > It _could_ show that the commit has some effect on runtime. > It _could_ show that it passes some (unavailable) regression test. > > IMO: None of those are really necessary here. > > > . > The variable bc_addr is repeated many times in the code and looks like magic number. I want to simplify the code by remoing unnecessary bc_addr. And I think it's better using eth_broadcast_addr() directly rather than using ether_addr_copy() + bc_addr. Thanks to Joe for the data. Thanks,