diff mbox

net: hix5hd2_gmac: avoid integer overload warning

Message ID 4752736.dePgPCNd9q@wuerfel
State Accepted, archived
Delegated to: David Miller
Headers show

Commit Message

Arnd Bergmann Oct. 16, 2015, 10 a.m. UTC 
BITS_RX_EN is an 'unsigned long' constant, so the ones complement of that
has bits set that do not fit into a 32-bit variable on 64-bit architectures,
which causes a harmless gcc warning:

drivers/net/ethernet/hisilicon/hix5hd2_gmac.c: In function 'hix5hd2_port_disable':
drivers/net/ethernet/hisilicon/hix5hd2_gmac.c:374:2: warning: large integer implicitly truncated to unsigned type [-Woverflow]
  writel_relaxed(~(BITS_RX_EN | BITS_TX_EN), priv->base + PORT_EN);

This adds a cast to (u32) to tell gcc that the code is indeed fine.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>


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Comments

David Laight Oct. 16, 2015, 11:14 a.m. UTC | #1 
From: Arnd Bergmann
> Sent: 16 October 2015 11:01
> BITS_RX_EN is an 'unsigned long' constant, so the ones complement of that
> has bits set that do not fit into a 32-bit variable on 64-bit architectures,
> which causes a harmless gcc warning:
...
>  static void hix5hd2_port_disable(struct hix5hd2_priv *priv)
>  {
> -	writel_relaxed(~(BITS_RX_EN | BITS_TX_EN), priv->base + PORT_EN);
> +	writel_relaxed(~(u32)(BITS_RX_EN | BITS_TX_EN), priv->base + PORT_EN);
>  	writel_relaxed(0, priv->base + DESC_WR_RD_ENA);

ISTM that just means that the constants shouldn't be 'long'.

	David

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Arnd Bergmann Oct. 16, 2015, 11:28 a.m. UTC | #2 
On Friday 16 October 2015 11:14:44 David Laight wrote:
> From: Arnd Bergmann
> > Sent: 16 October 2015 11:01
> > BITS_RX_EN is an 'unsigned long' constant, so the ones complement of that
> > has bits set that do not fit into a 32-bit variable on 64-bit architectures,
> > which causes a harmless gcc warning:
> ...
> >  static void hix5hd2_port_disable(struct hix5hd2_priv *priv)
> >  {
> > -     writel_relaxed(~(BITS_RX_EN | BITS_TX_EN), priv->base + PORT_EN);
> > +     writel_relaxed(~(u32)(BITS_RX_EN | BITS_TX_EN), priv->base + PORT_EN);
> >       writel_relaxed(0, priv->base + DESC_WR_RD_ENA);
> 
> ISTM that just means that the constants shouldn't be 'long'.

Right, but that would probably mean changing the BIT() macro or not using it
here. In the past I've argued against using that macro, but I've given
up that fight.

	Arnd
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Joe Perches Oct. 16, 2015, 6:04 p.m. UTC | #3 
On Fri, 2015-10-16 at 13:28 +0200, Arnd Bergmann wrote:
> On Friday 16 October 2015 11:14:44 David Laight wrote:
> > From: Arnd Bergmann
> > > Sent: 16 October 2015 11:01
> > > BITS_RX_EN is an 'unsigned long' constant, so the ones complement of that
> > > has bits set that do not fit into a 32-bit variable on 64-bit architectures,
> > > which causes a harmless gcc warning:
> > ...
> > >  static void hix5hd2_port_disable(struct hix5hd2_priv *priv)
> > >  {
> > > -     writel_relaxed(~(BITS_RX_EN | BITS_TX_EN), priv->base + PORT_EN);
> > > +     writel_relaxed(~(u32)(BITS_RX_EN | BITS_TX_EN), priv->base + PORT_EN);
> > >       writel_relaxed(0, priv->base + DESC_WR_RD_ENA);
> > 
> > ISTM that just means that the constants shouldn't be 'long'.
> 
> Right, but that would probably mean changing the BIT() macro or not using it
> here. In the past I've argued against using that macro, but I've given
> up that fight.

Fight on... (Somebody must have gone to USC here)

There might be value in a BIT_U32 macro.
Maybe BIT_U64 too.



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Sergei Shtylyov Oct. 16, 2015, 6:50 p.m. UTC | #4 
On 10/16/2015 09:04 PM, Joe Perches wrote:

>>>> BITS_RX_EN is an 'unsigned long' constant, so the ones complement of that
>>>> has bits set that do not fit into a 32-bit variable on 64-bit architectures,
>>>> which causes a harmless gcc warning:
>>> ...
>>>>   static void hix5hd2_port_disable(struct hix5hd2_priv *priv)
>>>>   {
>>>> -     writel_relaxed(~(BITS_RX_EN | BITS_TX_EN), priv->base + PORT_EN);
>>>> +     writel_relaxed(~(u32)(BITS_RX_EN | BITS_TX_EN), priv->base + PORT_EN);
>>>>        writel_relaxed(0, priv->base + DESC_WR_RD_ENA);
>>>
>>> ISTM that just means that the constants shouldn't be 'long'.
>>
>> Right, but that would probably mean changing the BIT() macro or not using it
>> here. In the past I've argued against using that macro, but I've given
>> up that fight.
>
> Fight on... (Somebody must have gone to USC here)
>
> There might be value in a BIT_U32 macro.
> Maybe BIT_U64 too.

    There's BIT_ULL() already.

MBR, Sergei

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Joe Perches Oct. 16, 2015, 9:22 p.m. UTC | #5 
On Fri, 2015-10-16 at 21:50 +0300, Sergei Shtylyov wrote:
> On 10/16/2015 09:04 PM, Joe Perches wrote:
> 
> >>>> BITS_RX_EN is an 'unsigned long' constant, so the ones complement of that
> >>>> has bits set that do not fit into a 32-bit variable on 64-bit architectures,
> >>>> which causes a harmless gcc warning:
> >>> ...
> >>>>   static void hix5hd2_port_disable(struct hix5hd2_priv *priv)
> >>>>   {
> >>>> -     writel_relaxed(~(BITS_RX_EN | BITS_TX_EN), priv->base + PORT_EN);
> >>>> +     writel_relaxed(~(u32)(BITS_RX_EN | BITS_TX_EN), priv->base + PORT_EN);
> >>>>        writel_relaxed(0, priv->base + DESC_WR_RD_ENA);
> >>>
> >>> ISTM that just means that the constants shouldn't be 'long'.
> >>
> >> Right, but that would probably mean changing the BIT() macro or not using it
> >> here. In the past I've argued against using that macro, but I've given
> >> up that fight.
> >
> > Fight on... (Somebody must have gone to USC here)
> >
> > There might be value in aefin BIT_U32 macro.
> > Maybe BIT_U64 too.
> 
>     There's BIT_ULL() already.

I know, but symmetry is good.
I think there'd be no harm in adding it.
Perhaps adding all the sized variants would be useful.

Something like:

#define BIT_OF_TYPE(type, nr)						\
({									\
	typeof(type) rtn;						\
	BUILD_BUG_ON(__builtin_constant_p(nr) &&			\
		     ((nr) < 0 ||					\
		      (nr) >= sizeof(type) * BITS_PER_BYTE));		\
	rtn = ((type)1) << (nr);					\
	rtn;								\
})

#define BIT_U8(nr)	BIT_OF_TYPE(u8, nr)
#define BIT_U16(nr)	BIT_OF_TYPE(u16, nr)
#define BIT_U32(nr)	BIT_OF_TYPE(u32, nr)
#define BIT_U64(nr)	BIT_OF_TYPE(u64, nr)


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Arnd Bergmann Oct. 16, 2015, 9:42 p.m. UTC | #6 
On Friday 16 October 2015 14:22:15 Joe Perches wrote:
> On Fri, 2015-10-16 at 21:50 +0300, Sergei Shtylyov wrote:
> > On 10/16/2015 09:04 PM, Joe Perches wrote:
> > 
> > >>>> BITS_RX_EN is an 'unsigned long' constant, so the ones complement of that
> > >>>> has bits set that do not fit into a 32-bit variable on 64-bit architectures,
> > >>>> which causes a harmless gcc warning:
> > >>> ...
> > >>>>   static void hix5hd2_port_disable(struct hix5hd2_priv *priv)
> > >>>>   {
> > >>>> -     writel_relaxed(~(BITS_RX_EN | BITS_TX_EN), priv->base + PORT_EN);
> > >>>> +     writel_relaxed(~(u32)(BITS_RX_EN | BITS_TX_EN), priv->base + PORT_EN);
> > >>>>        writel_relaxed(0, priv->base + DESC_WR_RD_ENA);
> > >>>
> > >>> ISTM that just means that the constants shouldn't be 'long'.
> > >>
> > >> Right, but that would probably mean changing the BIT() macro or not using it
> > >> here. In the past I've argued against using that macro, but I've given
> > >> up that fight.
> > >
> > > Fight on... (Somebody must have gone to USC here)

Ok, I'll try:

Please stop this nonsense!

;-)

> > > There might be value in aefin BIT_U32 macro.
> > > Maybe BIT_U64 too.
> > 
> >     There's BIT_ULL() already.
> 
> I know, but symmetry is good.
> I think there'd be no harm in adding it.
> Perhaps adding all the sized variants would be useful.
> 
> Something like:
> 
> #define BIT_OF_TYPE(type, nr)						\
> ({									\
> 	typeof(type) rtn;						\
> 	BUILD_BUG_ON(__builtin_constant_p(nr) &&			\
> 		     ((nr) < 0 ||					\
> 		      (nr) >= sizeof(type) * BITS_PER_BYTE));		\
> 	rtn = ((type)1) << (nr);					\
> 	rtn;								\
> })
> 
> #define BIT_U8(nr)	BIT_OF_TYPE(u8, nr)
> #define BIT_U16(nr)	BIT_OF_TYPE(u16, nr)
> #define BIT_U32(nr)	BIT_OF_TYPE(u32, nr)
> #define BIT_U64(nr)	BIT_OF_TYPE(u64, nr)

As I said, I'd rather see less uses of BIT() instead of more. While
using 'BIT(23)' is often than the open-coded '1 << 23', I wish more
people would write that as '0x00800000' instead. It's easier to
match with data sheets, and to compare to printk output, plus
it's non-ambiguous if you are dealing with data sheets that use
the IBM convention of counting the bits from the other end.

	Arnd
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David Miller Oct. 19, 2015, 3:01 a.m. UTC | #7 
From: Arnd Bergmann <arnd@arndb.de>
Date: Fri, 16 Oct 2015 12:00:51 +0200

> BITS_RX_EN is an 'unsigned long' constant, so the ones complement of that
> has bits set that do not fit into a 32-bit variable on 64-bit architectures,
> which causes a harmless gcc warning:
> 
> drivers/net/ethernet/hisilicon/hix5hd2_gmac.c: In function 'hix5hd2_port_disable':
> drivers/net/ethernet/hisilicon/hix5hd2_gmac.c:374:2: warning: large integer implicitly truncated to unsigned type [-Woverflow]
>   writel_relaxed(~(BITS_RX_EN | BITS_TX_EN), priv->base + PORT_EN);
> 
> This adds a cast to (u32) to tell gcc that the code is indeed fine.
> 
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>

Applied.
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diff mbox

Patch

diff --git a/drivers/net/ethernet/hisilicon/hix5hd2_gmac.c b/drivers/net/ethernet/hisilicon/hix5hd2_gmac.c
index a5e077eac99a..e51892d518ff 100644
--- a/drivers/net/ethernet/hisilicon/hix5hd2_gmac.c
+++ b/drivers/net/ethernet/hisilicon/hix5hd2_gmac.c
@@ -371,7 +371,7 @@  static void hix5hd2_port_enable(struct hix5hd2_priv *priv)
 
 static void hix5hd2_port_disable(struct hix5hd2_priv *priv)
 {
-	writel_relaxed(~(BITS_RX_EN | BITS_TX_EN), priv->base + PORT_EN);
+	writel_relaxed(~(u32)(BITS_RX_EN | BITS_TX_EN), priv->base + PORT_EN);
 	writel_relaxed(0, priv->base + DESC_WR_RD_ENA);
 }