linux-kernel - RE: [PATCH v3 -next 4/4] net: emaclite: Fix restricted cast warning of sparse

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Message-ID: <CH2PR02MB70008E426323BBF4EF3BCCA2C7190@CH2PR02MB7000.namprd02.prod.outlook.com>
Date:   Mon, 10 Feb 2020 14:55:20 +0000
From:   Radhey Shyam Pandey <radheys@...inx.com>
To:     Andrew Lunn <andrew@...n.ch>
CC:     "davem@...emloft.net" <davem@...emloft.net>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Anirudha Sarangi <anirudh@...inx.com>,
        Michal Simek <michals@...inx.com>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "mchehab+samsung@...nel.org" <mchehab+samsung@...nel.org>,
        John Linn <linnj@...inx.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: RE: [PATCH v3 -next 4/4] net: emaclite: Fix restricted cast warning
 of sparse

> -----Original Message-----
> From: Andrew Lunn <andrew@...n.ch>
> Sent: Friday, January 31, 2020 7:19 PM
> To: Radhey Shyam Pandey <radheys@...inx.com>
> Cc: davem@...emloft.net; netdev@...r.kernel.org; linux-
> kernel@...r.kernel.org; Anirudha Sarangi <anirudh@...inx.com>; Michal Simek
> <michals@...inx.com>; gregkh@...uxfoundation.org;
> mchehab+samsung@...nel.org; John Linn <linnj@...inx.com>; linux-arm-
> kernel@...ts.infradead.org
> Subject: Re: [PATCH v3 -next 4/4] net: emaclite: Fix restricted cast warning of
> sparse
> 
> On Fri, Jan 31, 2020 at 05:17:50PM +0530, Radhey Shyam Pandey wrote:
> > Explicitly cast xemaclite_readl return value when it's passed to ntohl.
> > Fixes below reported sparse warnings:
> >
> > xilinx_emaclite.c:411:24: sparse: sparse: cast to restricted __be32
> > xilinx_emaclite.c:420:36: sparse: sparse: cast to restricted __be32
> >
> > Signed-off-by: Radhey Shyam Pandey <radhey.shyam.pandey@...inx.com>
> > Reported-by: kbuild test robot <lkp@...el.com>
> > ---
> >  drivers/net/ethernet/xilinx/xilinx_emaclite.c | 5 +++--
> >  1 file changed, 3 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/net/ethernet/xilinx/xilinx_emaclite.c
> b/drivers/net/ethernet/xilinx/xilinx_emaclite.c
> > index 96e9d21..3273d4f 100644
> > --- a/drivers/net/ethernet/xilinx/xilinx_emaclite.c
> > +++ b/drivers/net/ethernet/xilinx/xilinx_emaclite.c
> > @@ -408,7 +408,8 @@ static u16 xemaclite_recv_data(struct net_local
> *drvdata, u8 *data, int maxlen)
> >
> >  	/* Get the protocol type of the ethernet frame that arrived
> >  	 */
> > -	proto_type = ((ntohl(xemaclite_readl(addr + XEL_HEADER_OFFSET +
> > +	proto_type = ((ntohl((__force __be32)xemaclite_readl(addr +
> > +			XEL_HEADER_OFFSET +
> >  			XEL_RXBUFF_OFFSET)) >> XEL_HEADER_SHIFT) &
> >  			XEL_RPLR_LENGTH_MASK);
> >
> > @@ -417,7 +418,7 @@ static u16 xemaclite_recv_data(struct net_local
> *drvdata, u8 *data, int maxlen)
> >  	 */
> >  	if (proto_type > ETH_DATA_LEN) {
> >  		if (proto_type == ETH_P_IP) {
> > -			length = ((ntohl(xemaclite_readl(addr +
> > +			length = ((ntohl((__force __be32)xemaclite_readl(addr
> +
> >  					XEL_HEADER_IP_LENGTH_OFFSET +
> >  					XEL_RXBUFF_OFFSET)) >>
> >  					XEL_HEADER_SHIFT) &
> 
> If i understand this code correctly, you need the ntohl because you
> are poking around inside the packet. All the other uses of
> xemaclite_readl() are for descriptors etc.
> 
> It would be cleaner if you defined a xemaclite_readlbe32. If you use
> ioread32be() it will do the endinness swap for you, so you don't need
> the ntohl() and the horrible cast.
Thanks for the review. Yes, defining xemaclite_readlbe32 would eliminate the
cast need.  I will address it in the next version. 

> 
>     Andrew