linux-kernel - Re: [RESEND PATCH v2 9/9] ath5k: Constify ioreadX() iomem argument (as in generic implementation)

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Message-ID: <20200224124744.GA1949@pi3>
Date:   Mon, 24 Feb 2020 13:47:44 +0100
From:   Krzysztof Kozlowski <krzk@...nel.org>
To:     Jiri Slaby <jirislaby@...il.com>
Cc:     Richard Henderson <rth@...ddle.net>,
        Ivan Kokshaysky <ink@...assic.park.msu.ru>,
        Matt Turner <mattst88@...il.com>,
        Alexey Brodkin <abrodkin@...opsys.com>,
        Vineet Gupta <vgupta@...opsys.com>,
        "James E.J. Bottomley" <James.Bottomley@...senpartnership.com>,
        Helge Deller <deller@....de>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Yoshinori Sato <ysato@...rs.sourceforge.jp>,
        Rich Felker <dalias@...c.org>,
        Dave Airlie <airlied@...hat.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Ben Skeggs <bskeggs@...hat.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Nick Kossifidis <mickflemm@...il.com>,
        Luis Chamberlain <mcgrof@...nel.org>,
        Kalle Valo <kvalo@...eaurora.org>,
        "David S. Miller" <davem@...emloft.net>,
        Dave Jiang <dave.jiang@...el.com>,
        Jon Mason <jdmason@...zu.us>, Allen Hubbe <allenbh@...il.com>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        Arnd Bergmann <arnd@...db.de>,
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Subject: Re: [RESEND PATCH v2 9/9] ath5k: Constify ioreadX() iomem argument
 (as in generic implementation)

On Thu, Feb 20, 2020 at 10:48:33AM +0100, Jiri Slaby wrote:
> On 19. 02. 20, 18:50, Krzysztof Kozlowski wrote:
> > The ioreadX() helpers have inconsistent interface.  On some architectures
> > void *__iomem address argument is a pointer to const, on some not.
> > 
> > Implementations of ioreadX() do not modify the memory under the address
> > so they can be converted to a "const" version for const-safety and
> > consistency among architectures.
> > 
> > Signed-off-by: Krzysztof Kozlowski <krzk@...nel.org>
> > Acked-by: Kalle Valo <kvalo@...eaurora.org>
> > ---
> >  drivers/net/wireless/ath/ath5k/ahb.c | 10 +++++-----
> >  1 file changed, 5 insertions(+), 5 deletions(-)
> > 
> > diff --git a/drivers/net/wireless/ath/ath5k/ahb.c b/drivers/net/wireless/ath/ath5k/ahb.c
> > index 2c9cec8b53d9..8bd01df369fb 100644
> > --- a/drivers/net/wireless/ath/ath5k/ahb.c
> > +++ b/drivers/net/wireless/ath/ath5k/ahb.c
> > @@ -138,18 +138,18 @@ static int ath_ahb_probe(struct platform_device *pdev)
> >  
> >  	if (bcfg->devid >= AR5K_SREV_AR2315_R6) {
> >  		/* Enable WMAC AHB arbitration */
> > -		reg = ioread32((void __iomem *) AR5K_AR2315_AHB_ARB_CTL);
> > +		reg = ioread32((const void __iomem *) AR5K_AR2315_AHB_ARB_CTL);
> 
> While I understand why the parameter of ioread32 should be const, I
> don't see a reason for these casts on the users' side. What does it
> bring except longer code to read?

Because the argument is an int:

drivers/net/wireless/ath/ath5k/ahb.c: In function ‘ath_ahb_probe’:
drivers/net/wireless/ath/ath5k/ahb.c:141:18: warning: passing argument 1 of ‘ioread32’ makes pointer from integer without a cast [-Wint-conversion]
   reg = ioread32(AR5K_AR2315_AHB_ARB_CTL);

Best regards,
Krzysztof