[PATCH] net: stmmac: xgmac: add missing parentheses to fix precendence error

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* [PATCH] net: stmmac: xgmac: add missing parentheses to fix precendence error
@ 2019-10-02 11:08 Colin King
  2019-10-02 13:33 ` Dan Carpenter
  0 siblings, 1 reply; 6+ messages in thread
From: Colin King @ 2019-10-02 11:08 UTC (permalink / raw)
  To: Giuseppe Cavallaro, Alexandre Torgue, Jose Abreu,
	David S . Miller, Maxime Coquelin, netdev, linux-stm32,
	linux-arm-kernel
  Cc: kernel-janitors, linux-kernel

From: Colin Ian King <colin.king@canonical.com>

The expression !(hw_cap & XGMAC_HWFEAT_RAVSEL) >> 10 is always zero, so
the masking operation is incorrect. Fix this by adding the missing
parentheses to correctly bind the negate operator on the entire expression.

Addresses-Coverity: ("Operands don't affect result")
Fixes: c2b69474d63b ("net: stmmac: xgmac: Correct RAVSEL field interpretation")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
---
 drivers/net/ethernet/stmicro/stmmac/dwxgmac2_dma.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/dwxgmac2_dma.c b/drivers/net/ethernet/stmicro/stmmac/dwxgmac2_dma.c
index 965cbe3e6f51..2e814aa64a5c 100644
--- a/drivers/net/ethernet/stmicro/stmmac/dwxgmac2_dma.c
+++ b/drivers/net/ethernet/stmicro/stmmac/dwxgmac2_dma.c
@@ -369,7 +369,7 @@ static void dwxgmac2_get_hw_feature(void __iomem *ioaddr,
 	dma_cap->eee = (hw_cap & XGMAC_HWFEAT_EEESEL) >> 13;
 	dma_cap->atime_stamp = (hw_cap & XGMAC_HWFEAT_TSSEL) >> 12;
 	dma_cap->av = (hw_cap & XGMAC_HWFEAT_AVSEL) >> 11;
-	dma_cap->av &= !(hw_cap & XGMAC_HWFEAT_RAVSEL) >> 10;
+	dma_cap->av &= !((hw_cap & XGMAC_HWFEAT_RAVSEL) >> 10);
 	dma_cap->arpoffsel = (hw_cap & XGMAC_HWFEAT_ARPOFFSEL) >> 9;
 	dma_cap->rmon = (hw_cap & XGMAC_HWFEAT_MMCSEL) >> 8;
 	dma_cap->pmt_magic_frame = (hw_cap & XGMAC_HWFEAT_MGKSEL) >> 7;
-- 
2.20.1


^ permalink raw reply related	[flat|nested] 6+ messages in thread

* Re: [PATCH] net: stmmac: xgmac: add missing parentheses to fix precendence error
  2019-10-02 11:08 [PATCH] net: stmmac: xgmac: add missing parentheses to fix precendence error Colin King
@ 2019-10-02 13:33 ` Dan Carpenter
  2019-10-02 13:40   ` Colin Ian King
  2019-10-02 13:42   ` Dan Carpenter
  0 siblings, 2 replies; 6+ messages in thread
From: Dan Carpenter @ 2019-10-02 13:33 UTC (permalink / raw)
  To: Colin King
  Cc: Giuseppe Cavallaro, Alexandre Torgue, Jose Abreu,
	David S . Miller, Maxime Coquelin, netdev, linux-stm32,
	linux-arm-kernel, kernel-janitors, linux-kernel

On Wed, Oct 02, 2019 at 12:08:49PM +0100, Colin King wrote:
> From: Colin Ian King <colin.king@canonical.com>
> 
> The expression !(hw_cap & XGMAC_HWFEAT_RAVSEL) >> 10 is always zero, so
> the masking operation is incorrect. Fix this by adding the missing
> parentheses to correctly bind the negate operator on the entire expression.
> 
> Addresses-Coverity: ("Operands don't affect result")
> Fixes: c2b69474d63b ("net: stmmac: xgmac: Correct RAVSEL field interpretation")
> Signed-off-by: Colin Ian King <colin.king@canonical.com>
> ---
>  drivers/net/ethernet/stmicro/stmmac/dwxgmac2_dma.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/stmicro/stmmac/dwxgmac2_dma.c b/drivers/net/ethernet/stmicro/stmmac/dwxgmac2_dma.c
> index 965cbe3e6f51..2e814aa64a5c 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/dwxgmac2_dma.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/dwxgmac2_dma.c
> @@ -369,7 +369,7 @@ static void dwxgmac2_get_hw_feature(void __iomem *ioaddr,
>  	dma_cap->eee = (hw_cap & XGMAC_HWFEAT_EEESEL) >> 13;
>  	dma_cap->atime_stamp = (hw_cap & XGMAC_HWFEAT_TSSEL) >> 12;
>  	dma_cap->av = (hw_cap & XGMAC_HWFEAT_AVSEL) >> 11;
> -	dma_cap->av &= !(hw_cap & XGMAC_HWFEAT_RAVSEL) >> 10;
> +	dma_cap->av &= !((hw_cap & XGMAC_HWFEAT_RAVSEL) >> 10);

There is no point to the shift at all.

regards,
dan carpenter


^ permalink raw reply	[flat|nested] 6+ messages in thread

* Re: [PATCH] net: stmmac: xgmac: add missing parentheses to fix precendence error
  2019-10-02 13:33 ` Dan Carpenter
@ 2019-10-02 13:40   ` Colin Ian King
  2019-10-02 13:42   ` Dan Carpenter
  1 sibling, 0 replies; 6+ messages in thread
From: Colin Ian King @ 2019-10-02 13:40 UTC (permalink / raw)
  To: Dan Carpenter
  Cc: Giuseppe Cavallaro, Alexandre Torgue, Jose Abreu,
	David S . Miller, Maxime Coquelin, netdev, linux-stm32,
	linux-arm-kernel, kernel-janitors, linux-kernel

On 02/10/2019 14:33, Dan Carpenter wrote:
> On Wed, Oct 02, 2019 at 12:08:49PM +0100, Colin King wrote:
>> From: Colin Ian King <colin.king@canonical.com>
>>
>> The expression !(hw_cap & XGMAC_HWFEAT_RAVSEL) >> 10 is always zero, so
>> the masking operation is incorrect. Fix this by adding the missing
>> parentheses to correctly bind the negate operator on the entire expression.
>>
>> Addresses-Coverity: ("Operands don't affect result")
>> Fixes: c2b69474d63b ("net: stmmac: xgmac: Correct RAVSEL field interpretation")
>> Signed-off-by: Colin Ian King <colin.king@canonical.com>
>> ---
>>  drivers/net/ethernet/stmicro/stmmac/dwxgmac2_dma.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/net/ethernet/stmicro/stmmac/dwxgmac2_dma.c b/drivers/net/ethernet/stmicro/stmmac/dwxgmac2_dma.c
>> index 965cbe3e6f51..2e814aa64a5c 100644
>> --- a/drivers/net/ethernet/stmicro/stmmac/dwxgmac2_dma.c
>> +++ b/drivers/net/ethernet/stmicro/stmmac/dwxgmac2_dma.c
>> @@ -369,7 +369,7 @@ static void dwxgmac2_get_hw_feature(void __iomem *ioaddr,
>>  	dma_cap->eee = (hw_cap & XGMAC_HWFEAT_EEESEL) >> 13;
>>  	dma_cap->atime_stamp = (hw_cap & XGMAC_HWFEAT_TSSEL) >> 12;
>>  	dma_cap->av = (hw_cap & XGMAC_HWFEAT_AVSEL) >> 11;
>> -	dma_cap->av &= !(hw_cap & XGMAC_HWFEAT_RAVSEL) >> 10;
>> +	dma_cap->av &= !((hw_cap & XGMAC_HWFEAT_RAVSEL) >> 10);
> 
> There is no point to the shift at all.

I must admit I was so focused on figuring out the original intent of the
code I totally missed that optimization step. I'll send a V2.

> 
> regards,
> dan carpenter
> 


^ permalink raw reply	[flat|nested] 6+ messages in thread

* Re: [PATCH] net: stmmac: xgmac: add missing parentheses to fix precendence error
  2019-10-02 13:33 ` Dan Carpenter
  2019-10-02 13:40   ` Colin Ian King
@ 2019-10-02 13:42   ` Dan Carpenter
  2019-10-02 13:53     ` Colin Ian King
  1 sibling, 1 reply; 6+ messages in thread
From: Dan Carpenter @ 2019-10-02 13:42 UTC (permalink / raw)
  To: Colin King
  Cc: Giuseppe Cavallaro, Alexandre Torgue, Jose Abreu,
	David S . Miller, Maxime Coquelin, netdev, linux-stm32,
	linux-arm-kernel, kernel-janitors, linux-kernel

On Wed, Oct 02, 2019 at 04:33:57PM +0300, Dan Carpenter wrote:
> On Wed, Oct 02, 2019 at 12:08:49PM +0100, Colin King wrote:
> > From: Colin Ian King <colin.king@canonical.com>
> > 
> > The expression !(hw_cap & XGMAC_HWFEAT_RAVSEL) >> 10 is always zero, so
> > the masking operation is incorrect. Fix this by adding the missing
> > parentheses to correctly bind the negate operator on the entire expression.
> > 
> > Addresses-Coverity: ("Operands don't affect result")
> > Fixes: c2b69474d63b ("net: stmmac: xgmac: Correct RAVSEL field interpretation")
> > Signed-off-by: Colin Ian King <colin.king@canonical.com>
> > ---
> >  drivers/net/ethernet/stmicro/stmmac/dwxgmac2_dma.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/net/ethernet/stmicro/stmmac/dwxgmac2_dma.c b/drivers/net/ethernet/stmicro/stmmac/dwxgmac2_dma.c
> > index 965cbe3e6f51..2e814aa64a5c 100644
> > --- a/drivers/net/ethernet/stmicro/stmmac/dwxgmac2_dma.c
> > +++ b/drivers/net/ethernet/stmicro/stmmac/dwxgmac2_dma.c
> > @@ -369,7 +369,7 @@ static void dwxgmac2_get_hw_feature(void __iomem *ioaddr,
> >  	dma_cap->eee = (hw_cap & XGMAC_HWFEAT_EEESEL) >> 13;
> >  	dma_cap->atime_stamp = (hw_cap & XGMAC_HWFEAT_TSSEL) >> 12;
> >  	dma_cap->av = (hw_cap & XGMAC_HWFEAT_AVSEL) >> 11;
> > -	dma_cap->av &= !(hw_cap & XGMAC_HWFEAT_RAVSEL) >> 10;
> > +	dma_cap->av &= !((hw_cap & XGMAC_HWFEAT_RAVSEL) >> 10);
> 
> There is no point to the shift at all.

Sorry I meant to say it should be a bitwise NOT, right?  I was just
looking at some other dma_cap stuff that did this same thing...  I can't
find it now...

regards,
dan carpenter


^ permalink raw reply	[flat|nested] 6+ messages in thread

* Re: [PATCH] net: stmmac: xgmac: add missing parentheses to fix precendence error
  2019-10-02 13:42   ` Dan Carpenter
@ 2019-10-02 13:53     ` Colin Ian King
  2019-10-02 14:07       ` Dan Carpenter
  0 siblings, 1 reply; 6+ messages in thread
From: Colin Ian King @ 2019-10-02 13:53 UTC (permalink / raw)
  To: Dan Carpenter
  Cc: Giuseppe Cavallaro, Alexandre Torgue, Jose Abreu,
	David S . Miller, Maxime Coquelin, netdev, linux-stm32,
	linux-arm-kernel, kernel-janitors, linux-kernel

On 02/10/2019 14:42, Dan Carpenter wrote:
> On Wed, Oct 02, 2019 at 04:33:57PM +0300, Dan Carpenter wrote:
>> On Wed, Oct 02, 2019 at 12:08:49PM +0100, Colin King wrote:
>>> From: Colin Ian King <colin.king@canonical.com>
>>>
>>> The expression !(hw_cap & XGMAC_HWFEAT_RAVSEL) >> 10 is always zero, so
>>> the masking operation is incorrect. Fix this by adding the missing
>>> parentheses to correctly bind the negate operator on the entire expression.
>>>
>>> Addresses-Coverity: ("Operands don't affect result")
>>> Fixes: c2b69474d63b ("net: stmmac: xgmac: Correct RAVSEL field interpretation")
>>> Signed-off-by: Colin Ian King <colin.king@canonical.com>
>>> ---
>>>  drivers/net/ethernet/stmicro/stmmac/dwxgmac2_dma.c | 2 +-
>>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/net/ethernet/stmicro/stmmac/dwxgmac2_dma.c b/drivers/net/ethernet/stmicro/stmmac/dwxgmac2_dma.c
>>> index 965cbe3e6f51..2e814aa64a5c 100644
>>> --- a/drivers/net/ethernet/stmicro/stmmac/dwxgmac2_dma.c
>>> +++ b/drivers/net/ethernet/stmicro/stmmac/dwxgmac2_dma.c
>>> @@ -369,7 +369,7 @@ static void dwxgmac2_get_hw_feature(void __iomem *ioaddr,
>>>  	dma_cap->eee = (hw_cap & XGMAC_HWFEAT_EEESEL) >> 13;
>>>  	dma_cap->atime_stamp = (hw_cap & XGMAC_HWFEAT_TSSEL) >> 12;
>>>  	dma_cap->av = (hw_cap & XGMAC_HWFEAT_AVSEL) >> 11;
>>> -	dma_cap->av &= !(hw_cap & XGMAC_HWFEAT_RAVSEL) >> 10;
>>> +	dma_cap->av &= !((hw_cap & XGMAC_HWFEAT_RAVSEL) >> 10);
>>
>> There is no point to the shift at all.
> 
> Sorry I meant to say it should be a bitwise NOT, right?  I was just
> looking at some other dma_cap stuff that did this same thing...  I can't
> find it now...

In drivers/net/ethernet/stmicro/stmmac/stmmac_tc.c it is being used like
a boolean and not a bitmask'd value:

        if (!priv->dma_cap.av)

so the original logic is to do boolean flag merging rather than bit-wise
logic.

> 
> regards,
> dan carpenter
> 


^ permalink raw reply	[flat|nested] 6+ messages in thread

* Re: [PATCH] net: stmmac: xgmac: add missing parentheses to fix precendence error
  2019-10-02 13:53     ` Colin Ian King
@ 2019-10-02 14:07       ` Dan Carpenter
  0 siblings, 0 replies; 6+ messages in thread
From: Dan Carpenter @ 2019-10-02 14:07 UTC (permalink / raw)
  To: Colin Ian King
  Cc: Giuseppe Cavallaro, Alexandre Torgue, Jose Abreu,
	David S . Miller, Maxime Coquelin, netdev, linux-stm32,
	linux-arm-kernel, kernel-janitors, linux-kernel

On Wed, Oct 02, 2019 at 02:53:17PM +0100, Colin Ian King wrote:
> On 02/10/2019 14:42, Dan Carpenter wrote:
> > On Wed, Oct 02, 2019 at 04:33:57PM +0300, Dan Carpenter wrote:
> >> On Wed, Oct 02, 2019 at 12:08:49PM +0100, Colin King wrote:
> >>> From: Colin Ian King <colin.king@canonical.com>
> >>>
> >>> The expression !(hw_cap & XGMAC_HWFEAT_RAVSEL) >> 10 is always zero, so
> >>> the masking operation is incorrect. Fix this by adding the missing
> >>> parentheses to correctly bind the negate operator on the entire expression.
> >>>
> >>> Addresses-Coverity: ("Operands don't affect result")
> >>> Fixes: c2b69474d63b ("net: stmmac: xgmac: Correct RAVSEL field interpretation")
> >>> Signed-off-by: Colin Ian King <colin.king@canonical.com>
> >>> ---
> >>>  drivers/net/ethernet/stmicro/stmmac/dwxgmac2_dma.c | 2 +-
> >>>  1 file changed, 1 insertion(+), 1 deletion(-)
> >>>
> >>> diff --git a/drivers/net/ethernet/stmicro/stmmac/dwxgmac2_dma.c b/drivers/net/ethernet/stmicro/stmmac/dwxgmac2_dma.c
> >>> index 965cbe3e6f51..2e814aa64a5c 100644
> >>> --- a/drivers/net/ethernet/stmicro/stmmac/dwxgmac2_dma.c
> >>> +++ b/drivers/net/ethernet/stmicro/stmmac/dwxgmac2_dma.c
> >>> @@ -369,7 +369,7 @@ static void dwxgmac2_get_hw_feature(void __iomem *ioaddr,
> >>>  	dma_cap->eee = (hw_cap & XGMAC_HWFEAT_EEESEL) >> 13;
> >>>  	dma_cap->atime_stamp = (hw_cap & XGMAC_HWFEAT_TSSEL) >> 12;
> >>>  	dma_cap->av = (hw_cap & XGMAC_HWFEAT_AVSEL) >> 11;
> >>> -	dma_cap->av &= !(hw_cap & XGMAC_HWFEAT_RAVSEL) >> 10;
> >>> +	dma_cap->av &= !((hw_cap & XGMAC_HWFEAT_RAVSEL) >> 10);
> >>
> >> There is no point to the shift at all.
> > 
> > Sorry I meant to say it should be a bitwise NOT, right?  I was just
> > looking at some other dma_cap stuff that did this same thing...  I can't
> > find it now...
> 
> In drivers/net/ethernet/stmicro/stmmac/stmmac_tc.c it is being used like
> a boolean and not a bitmask'd value:
> 
>         if (!priv->dma_cap.av)
> 
> so the original logic is to do boolean flag merging rather than bit-wise
> logic.

Oh yeah.  Thanks.  This code is hard to read.

It would be better to just write it like this:

	if (hw_cap & XGMAC_HWFEAT_AVSEL) && !(hw_cap & XGMAC_HWFEAT_RAVSEL)
		dma_cap->av = true;
	else
		dma_cap->av = false;

All these very shifts are concise but they introduce bugs like this one
you have found.

regards,
dan carpenter


^ permalink raw reply	[flat|nested] 6+ messages in thread

end of thread, other threads:[~2019-10-02 14:08 UTC | newest]

Thread overview: 6+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2019-10-02 11:08 [PATCH] net: stmmac: xgmac: add missing parentheses to fix precendence error Colin King
2019-10-02 13:33 ` Dan Carpenter
2019-10-02 13:40   ` Colin Ian King
2019-10-02 13:42   ` Dan Carpenter
2019-10-02 13:53     ` Colin Ian King
2019-10-02 14:07       ` Dan Carpenter

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