linux-kernel - Re: [PATCH RFC net-next v2 03/12] net: mdio: mdiobus

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Message-ID: <Y7SqCRkYkhQCLs8z@shell.armlinux.org.uk>
Date:   Tue, 3 Jan 2023 22:19:53 +0000
From:   "Russell King (Oracle)" <linux@...linux.org.uk>
To:     Michael Walle <michael@...le.cc>
Cc:     Heiner Kallweit <hkallweit1@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Jose Abreu <Jose.Abreu@...opsys.com>,
        Sergey Shtylyov <s.shtylyov@....ru>,
        Wei Fang <wei.fang@....com>,
        Shenwei Wang <shenwei.wang@....com>,
        Clark Wang <xiaoning.wang@....com>,
        NXP Linux Team <linux-imx@....com>,
        Sean Wang <sean.wang@...iatek.com>,
        Landen Chao <Landen.Chao@...iatek.com>,
        DENG Qingfang <dqfext@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Vladimir Oltean <olteanv@...il.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-renesas-soc@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, Andrew Lunn <andrew@...n.ch>,
        Geert Uytterhoeven <geert+renesas@...der.be>
Subject: Re: [PATCH RFC net-next v2 03/12] net: mdio: mdiobus_register:
 update validation test

Hi Michael,

On Tue, Jan 03, 2023 at 11:21:08AM +0100, Michael Walle wrote:
> Hi Russell,
> 
> Am 2023-01-03 11:13, schrieb Russell King (Oracle):
> > On Wed, Dec 28, 2022 at 12:07:19AM +0100, Michael Walle wrote:
> > > +	if (!bus || !bus->name)
> > > +		return -EINVAL;
> > > +
> > > +	/* An access method always needs both read and write operations */
> > > +	if ((bus->read && !bus->write) ||
> > > +	    (!bus->read && bus->write) ||
> > > +	    (bus->read_c45 && !bus->write_c45) ||
> > > +	    (!bus->read_c45 && bus->write_c45))
> > 
> > I wonder whether the following would be even more readable:
> > 
> > 	if (!bus->read != !bus->write || !bus->read_c45 != !bus->write_c45)
> 
> That's what Andrew had originally. But there was a comment from Sergey [1]
> which I agree with. I had a hard time wrapping my head around that, so I
> just listed all the possible bad cases.

The only reason I suggested it was because when looked at your code,
it also took several reads to work out what it was trying to do!

Would using !!bus->read != !!bus->write would help or make it worse,
!!ptr being the more normal way to convert something to a boolean?

-- 
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