linux-kernel - Re: [PATCH v3] usb: musb: remove unused variable 'devctl'

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Date:   Thu, 10 Dec 2020 16:01:03 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Sergei Shtylyov <sergei.shtylyov@...il.com>
Cc:     min.guo@...iatek.com, Bin Liu <b-liu@...com>,
        Alan Stern <stern@...land.harvard.edu>,
        Matthias Brugger <matthias.bgg@...il.com>,
        chunfeng.yun@...iatek.com, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org
Subject: Re: [PATCH v3] usb: musb: remove unused variable 'devctl'

On Tue, Nov 24, 2020 at 12:13:42PM +0300, Sergei Shtylyov wrote:
> Hello!
> 
> On 24.11.2020 11:49, min.guo@...iatek.com wrote:
> 
> > From: Min Guo <min.guo@...iatek.com>
> > 
> > Remove unused 'devctl' variable to fix compile warnings:
> > 
> >      drivers/usb/musb/musbhsdma.c: In function 'dma_controller_irq':
> >      drivers/usb/musb/musbhsdma.c:324:8: warning: variable 'devctl' set
> >      but not used [-Wunused-but-set-variable]
> > 
> > Signed-off-by: Min Guo <min.guo@...iatek.com>
> > ---
> > changes in v3
> > suggested by Greg Kroah-Hartman:
> > Add a comment.
> > 
> > changes in v2
> > suggested by Alan Stern:
> > Add void before musb_read to indicate that the register MUSB_DEVCTL
> > was intended to be read and discarded.
> > ---
> >   drivers/usb/musb/musbhsdma.c | 8 +++++---
> >   1 file changed, 5 insertions(+), 3 deletions(-)
> > 
> > diff --git a/drivers/usb/musb/musbhsdma.c b/drivers/usb/musb/musbhsdma.c
> > index 0aacfc8be5a1..2a345b4ad015 100644
> > --- a/drivers/usb/musb/musbhsdma.c
> > +++ b/drivers/usb/musb/musbhsdma.c
> [...]
> > @@ -336,7 +334,11 @@ irqreturn_t dma_controller_irq(int irq, void *private_data)
> >   						< musb_channel->len) ?
> >   					"=> reconfig 0" : "=> complete");
> > -				devctl = musb_readb(mbase, MUSB_DEVCTL);
> > +				/*
> > +				 * Some hardware may need to read the
> > +				 * MUSB_DEVCTL register once to take effect.
> > +				 */
> > +				(void)musb_readb(mbase, MUSB_DEVCTL);
> 
>    Hm, forcibly reading DevCtl in the DMA driver... sounds quite
> nonsensically. Lemme take a look...

What happened to your look?

thanks,

greg k-h