linux-kernel - Re: [PATCH] usb: mtu3: cleanup with list_first_entry_or

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Date:   Thu, 25 May 2017 14:26:20 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Chunfeng Yun <chunfeng.yun@...iatek.com>
Cc:     Masahiro Yamada <yamada.masahiro@...ionext.com>,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] usb: mtu3: cleanup with list_first_entry_or_null()

On Mon, May 22, 2017 at 09:21:33AM +0800, Chunfeng Yun wrote:
> Hi,
> On Sat, 2017-05-20 at 21:19 +0200, Greg Kroah-Hartman wrote:
> > On Sun, May 21, 2017 at 02:05:31AM +0900, Masahiro Yamada wrote:
> > > The combo of list_empty() and list_first_entry() can be replaced with
> > > list_first_entry_or_null().
> > > 
> > > Signed-off-by: Masahiro Yamada <yamada.masahiro@...ionext.com>
> > > ---
> > > 
> > >  drivers/usb/mtu3/mtu3.h | 8 ++------
> > >  1 file changed, 2 insertions(+), 6 deletions(-)
> > > 
> > > diff --git a/drivers/usb/mtu3/mtu3.h b/drivers/usb/mtu3/mtu3.h
> > > index aa6fd6a..7b6dc23 100644
> > > --- a/drivers/usb/mtu3/mtu3.h
> > > +++ b/drivers/usb/mtu3/mtu3.h
> > > @@ -356,12 +356,8 @@ static inline struct mtu3_ep *to_mtu3_ep(struct usb_ep *ep)
> > >  
> > >  static inline struct mtu3_request *next_request(struct mtu3_ep *mep)
> > >  {
> > > -	struct list_head *queue = &mep->req_list;
> > > -
> > > -	if (list_empty(queue))
> > > -		return NULL;
> > > -
> > > -	return list_first_entry(queue, struct mtu3_request, list);
> > > +	return list_first_entry_or_null(&mep->req_list, struct mtu3_request,
> > > +					list);
> > 
> > Even better, why is this an inlined function at all?  Why not just have
> > it "open coded" everywhere it is used?
> > 
> This can avoid repeated function definition, currently it is used in
> three files.

Ok, makes sense.

greg k-h