linux-kernel - Re: [PATCH -next 2/2] staging: r8188eu: use eth_broadcast

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Message-ID: <20210609065302.GA1500@agape.jhs>
Date:   Wed, 9 Jun 2021 08:53:03 +0200
From:   Fabio Aiuto <fabioaiuto83@...il.com>
To:     Liu Shixin <liushixin2@...wei.com>
Cc:     Joe Perches <joe@...ches.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-staging@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH -next 2/2] staging: r8188eu: use eth_broadcast_addr() to
 assign broadcast address

Hi Liu,

On Wed, Jun 09, 2021 at 11:01:18AM +0800, Liu Shixin wrote:
> 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,
> 
> 
> 

I would change the subject line using the proper driver name: 

	'staging: rtl8188eu: ...'

and not the compiled module name that I think it needs to be fixed (r8188eu).

Thank you,

fabio