linux-kernel - Re: [PATCH] staging: rtl8723bs: do not use assignment in if condition

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Message-ID: <36a7227189b8c7602dd9ffd21a5369b7029e61f1.camel@perches.com>
Date:   Fri, 22 Jun 2018 10:28:45 -0700
From:   Joe Perches <joe@...ches.com>
To:     Michael Straube <michael.straube@...teo.de>,
        Dan Carpenter <dan.carpenter@...cle.com>
Cc:     gregkh@...uxfoundation.org, devel@...verdev.osuosl.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] staging: rtl8723bs: do not use assignment in if
 condition

On Fri, 2018-06-22 at 14:48 +0200, Michael Straube wrote:
> On 06/22/18 12:57, Dan Carpenter wrote:
> > On Fri, Jun 22, 2018 at 03:54:22AM -0700, Joe Perches wrote:
> > > On Fri, 2018-06-22 at 13:40 +0300, Dan Carpenter wrote:
> > > > On Thu, Jun 21, 2018 at 08:22:30PM +0200, Michael Straube wrote:
> > > > > Fix checkpatch error 'do not use assignment in if condition'.
> > > []
> > > > > diff --git a/drivers/staging/rtl8723bs/core/rtw_ieee80211.c b/drivers/staging/rtl8723bs/core/rtw_ieee80211.c
> > > > > index e55895632921..87a4ced41028 100644
> > > > > --- a/drivers/staging/rtl8723bs/core/rtw_ieee80211.c
> > > > > +++ b/
> > > > > @@ -1181,9 +1181,8 @@ void rtw_macaddr_cfg(struct device *dev, u8 *mac_addr)
> > > > >   	     (mac[3] == 0xff) && (mac[4] == 0xff) && (mac[5] == 0xff)) ||
> > > > >   	    ((mac[0] == 0x00) && (mac[1] == 0x00) && (mac[2] == 0x00) &&
> > > > >   	     (mac[3] == 0x00) && (mac[4] == 0x00) && (mac[5] == 0x00))) {
> > > 
> > > Should also use is_broadcast_ether_addr and is_zero_ether_addr
> > > 
> > > > > -		if (np &&
> > > > > -		    (addr = of_get_property(np, "local-mac-address", &len)) &&
> > > > > -		    len == ETH_ALEN) {
> > > > > +		addr = of_get_property(np, "local-mac-address", &len);
> > > > > +		if (np && addr && len == ETH_ALEN) {
> > > > 
> > > > You can remove the "np" check.
> > > > 
> > > > 		if (addr && len == ETH_ALEN) {
> > > 
> > > It looks more like the rewrite is incorrect
> > > as np is tested before of_get_property
> > > 
> > 
> > That's what I was worried about too, but if "np" is NULL then
> > of_get_property() just returns NULL so it's fine.
> 
> So it should be this?
> 
>          if (((mac[0] == 0xff) && (mac[1] == 0xff) && (mac[2] == 0xff) &&
>               (mac[3] == 0xff) && (mac[4] == 0xff) && (mac[5] == 0xff)) ||
>              ((mac[0] == 0x00) && (mac[1] == 0x00) && (mac[2] == 0x00) &&
>               (mac[3] == 0x00) && (mac[4] == 0x00) && (mac[5] == 0x00)) &&
>              (is_broadcast_ether_addr(mac) || is_zero_ether_addr(mac))) {

No as the mac[] tests are the same as is_<foo>_ether_addr
and there's nothing really objectionable about embedding
the assignment in the if here.

Output from checkpatch is not gospel and can be ignored
whenever appropriate.

I think the below is ok:

	if ((is_broadcast_ether_addr(mac) || is_zero_ether_addr(mac)) &&
	    ((addr = of_get_property(np, "local-mac-address", &len)) &&
	     len == ETH_ALEN))
		memcpy(mac_addr, addr, ETH_ALEN);
	else
		memcpy(mac_addr, ""\x00\xe0\x4c\x87\x00\x00", ETH_ALEN);

Although the last memcpy of a fixed mac address could
probably use eth_random_addr to reduce the likelihood
of mac address collision so maybe

	if ((is_broadcast_ether_addr(mac) || is_zero_ether_addr(mac)) &&
	    ((addr = of_get_property(np, "local-mac-address", &len)) &&
	
     len == ETH_ALEN))
		memcpy(mac_addr, addr, ETH_ALEN);
	else
		eth_random_addr(mac_addr);

> If yes, I'm not sure how to proceed as these are the very first patches I send.
> Should I send a v2 patch with both changes or just a v2 with "np" removed and
> another one for adding 'is_broadcast_ether_addr' and 'is_zero_ether_addr' checks?

I'd send 1 patch.