linux-kernel - Re: [PATCH net-next] net: ethernet: ti: cpdma: rate is not changed

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Message-ID: <20171207194855.GA3022@khorivan>
Date:   Thu, 7 Dec 2017 21:48:56 +0200
From:   Ivan Khoronzhuk <ivan.khoronzhuk@...aro.org>
To:     David Miller <davem@...emloft.net>
Cc:     grygorii.strashko@...com, netdev@...r.kernel.org,
        linux-omap@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next] net: ethernet: ti: cpdma: rate is not changed -
 correct case

On Wed, Dec 06, 2017 at 04:35:45PM -0500, David Miller wrote:
> From: Ivan Khoronzhuk <ivan.khoronzhuk@...aro.org>
> Date: Wed,  6 Dec 2017 16:41:18 +0200
> 
> > If rate is the same as set it's correct case.
> > 
> > Signed-off-by: Ivan Khoronzhuk <ivan.khoronzhuk@...aro.org>
> > ---
> > Based on net-next/master
> > 
> >  drivers/net/ethernet/ti/davinci_cpdma.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/net/ethernet/ti/davinci_cpdma.c b/drivers/net/ethernet/ti/davinci_cpdma.c
> > index e4d6edf..dbe9167 100644
> > --- a/drivers/net/ethernet/ti/davinci_cpdma.c
> > +++ b/drivers/net/ethernet/ti/davinci_cpdma.c
> > @@ -841,7 +841,7 @@ int cpdma_chan_set_rate(struct cpdma_chan *ch, u32 rate)
> >  		return -EINVAL;
> >  
> >  	if (ch->rate == rate)
> > -		return rate;
> > +		return 0;
> 
> Looking at the one and only caller of this function, cpsw_ndo_set_tx_maxrate, it
> makes sure this can never, ever, happen.
In current circumstances yes, it will never happen.
But I caught it while adding related code and better return 0 if upper caller
doesn't have such check. Suppose that cpdma module is responsible for itself
and if it's critical I can send this patch along with whole related series.

> 
> So I would instead remove this check completely since it can never trigger.

-- 
Regards,
Ivan Khoronzhuk