linux-kernel - Re: [PATCH 4/4] staging: r8188eu: use htons macro instead of __constant

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Message-ID: <Y2Z6h4CvyujWBkZJ@qemulion>
Date:   Sat, 5 Nov 2022 20:30:23 +0530
From:   Deepak R Varma <drv@...lo.com>
To:     Joe Perches <joe@...ches.com>
Cc:     outreachy@...ts.linux.dev, Larry.Finger@...inger.net,
        phil@...lpotter.co.uk, paskripkin@...il.com,
        gregkh@...uxfoundation.org, linux-staging@...ts.linux.dev,
        linux-kernel@...r.kernel.org, kumarpraveen@...ux.microsoft.com,
        saurabh.truth@...il.com
Subject: Re: [PATCH 4/4] staging: r8188eu: use htons macro instead of
 __constant_htons

On Tue, Oct 18, 2022 at 11:08:06PM -0700, Joe Perches wrote:
> On Mon, 2022-10-17 at 18:54 +0530, Deepak R Varma wrote:
> > Macro "htons" is more efficiant and clearer. It should be used for
> > constants instead of the __contast_htons macro. Resolves following
>
> typo: __constant_htons
>
> > checkpatch script complaint:
> > 	WARNING: __constant_htons should be htons
> []
> > diff --git a/drivers/staging/r8188eu/core/rtw_br_ext.c b/drivers/staging/r8188eu/core/rtw_br_ext.c
> []
> > @@ -612,14 +612,14 @@ void dhcp_flag_bcast(struct adapter *priv, struct sk_buff *skb)
> >  	if (!priv->ethBrExtInfo.dhcp_bcst_disable) {
> >  		__be16 protocol = *((__be16 *)(skb->data + 2 * ETH_ALEN));
> >
> > -		if (protocol == __constant_htons(ETH_P_IP)) { /*  IP */
> > +		if (protocol == htons(ETH_P_IP)) { /*  IP */
> >  			struct iphdr *iph = (struct iphdr *)(skb->data + ETH_HLEN);
> >
> >  			if (iph->protocol == IPPROTO_UDP) { /*  UDP */
> >  				struct udphdr *udph = (struct udphdr *)((size_t)iph + (iph->ihl << 2));
> >
> > -				if ((udph->source == __constant_htons(CLIENT_PORT)) &&
> > -				    (udph->dest == __constant_htons(SERVER_PORT))) { /*  DHCP request */
> > +				if ((udph->source == htons(CLIENT_PORT)) &&
> > +				    (udph->dest == htons(SERVER_PORT))) { /*  DHCP request */
>
> OK, this bit seems fine
>
> >  					struct dhcpMessage *dhcph =
> >  						(struct dhcpMessage *)((size_t)udph + sizeof(struct udphdr));
>
> IMO: this existing code however is ugly.
>      Casting a pointer to a size_t isn't great.

Hello Joe,
Other thank looking ugly, is there any impact / risk associated with such
casting? I tried to look for the reasons myself but did not find anything
relevant or to the point.

Thank you,
./drv

>
> Perhaps:
>
> 				struct dhcpMessage *dhcp;
>
> 				dhcp = (void *)udhp + sizeof(struct udphdr);
>
> in a separate patch.
>
> > 					u32 cookie = be32_to_cpu((__be32)dhcph->cookie);
>
> And dhcph->cookie already is a __be32 so the cast is pointless.
>
> drivers/staging/r8188eu/core/rtw_br_ext.c-598-  __be32 cookie;
>