[PATCH] PCI: brcmstb: Fix control flow issue

[PATCH] PCI: brcmstb: Fix control flow issue

[Qianqiang Liu]

The type of "num_inbound_wins" is "u8", so the less-than-zero
comparison of an unsigned value is never true.

Signed-off-by: Qianqiang Liu <qianqiang.liu@163.com>
---
 drivers/pci/controller/pcie-brcmstb.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/pci/controller/pcie-brcmstb.c b/drivers/pci/controller/pcie-brcmstb.c
index 55311dc47615..3e4572c3eeb1 100644
--- a/drivers/pci/controller/pcie-brcmstb.c
+++ b/drivers/pci/controller/pcie-brcmstb.c
@@ -1090,9 +1090,11 @@ static int brcm_pcie_setup(struct brcm_pcie *pcie)
 	u32p_replace_bits(&tmp, 1, PCIE_MISC_MISC_CTRL_PCIE_RCB_64B_MODE_MASK);
 	writel(tmp, base + PCIE_MISC_MISC_CTRL);
 
-	num_inbound_wins = brcm_pcie_get_inbound_wins(pcie, inbound_wins);
-	if (num_inbound_wins < 0)
-		return num_inbound_wins;
+	ret = brcm_pcie_get_inbound_wins(pcie, inbound_wins);
+	if (ret < 0)
+		return ret;
+
+	num_inbound_wins = (u8)ret;
 
 	set_inbound_win_registers(pcie, inbound_wins, num_inbound_wins);
 
-- 
2.39.2

Re: [PATCH] PCI: brcmstb: Fix control flow issue

[Bjorn Helgaas]

On Wed, Sep 11, 2024 at 10:50:59AM +0800, Qianqiang Liu wrote:
> The type of "num_inbound_wins" is "u8", so the less-than-zero
> comparison of an unsigned value is never true.

I think this was fixed slightly differently but with the same effect;
please check this to make sure:

https://git.kernel.org/pub/scm/linux/kernel/git/pci/pci.git/tree/drivers/pci/controller/pcie-brcmstb.c?h=controller/brcmstb#n1034

> ---
>  drivers/pci/controller/pcie-brcmstb.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/pci/controller/pcie-brcmstb.c b/drivers/pci/controller/pcie-brcmstb.c
> index 55311dc47615..3e4572c3eeb1 100644
> --- a/drivers/pci/controller/pcie-brcmstb.c
> +++ b/drivers/pci/controller/pcie-brcmstb.c
> @@ -1090,9 +1090,11 @@ static int brcm_pcie_setup(struct brcm_pcie *pcie)
>  	u32p_replace_bits(&tmp, 1, PCIE_MISC_MISC_CTRL_PCIE_RCB_64B_MODE_MASK);
>  	writel(tmp, base + PCIE_MISC_MISC_CTRL);
>  
> -	num_inbound_wins = brcm_pcie_get_inbound_wins(pcie, inbound_wins);
> -	if (num_inbound_wins < 0)
> -		return num_inbound_wins;
> +	ret = brcm_pcie_get_inbound_wins(pcie, inbound_wins);
> +	if (ret < 0)
> +		return ret;
> +
> +	num_inbound_wins = (u8)ret;
>  
>  	set_inbound_win_registers(pcie, inbound_wins, num_inbound_wins);
>  
> -- 
> 2.39.2
> 

Re: [PATCH] PCI: brcmstb: Fix control flow issue

[Qianqiang Liu]

On Wed, Sep 11, 2024 at 08:44:36AM -0500, Bjorn Helgaas wrote:
> On Wed, Sep 11, 2024 at 10:50:59AM +0800, Qianqiang Liu wrote:
> > The type of "num_inbound_wins" is "u8", so the less-than-zero
> > comparison of an unsigned value is never true.
> 
> I think this was fixed slightly differently but with the same effect;
> please check this to make sure:
> 
> https://git.kernel.org/pub/scm/linux/kernel/git/pci/pci.git/tree/drivers/pci/controller/pcie-brcmstb.c?h=controller/brcmstb#n1034
> 
> > ---
> >  drivers/pci/controller/pcie-brcmstb.c | 8 +++++---
> >  1 file changed, 5 insertions(+), 3 deletions(-)
> > 
> > diff --git a/drivers/pci/controller/pcie-brcmstb.c b/drivers/pci/controller/pcie-brcmstb.c
> > index 55311dc47615..3e4572c3eeb1 100644
> > --- a/drivers/pci/controller/pcie-brcmstb.c
> > +++ b/drivers/pci/controller/pcie-brcmstb.c
> > @@ -1090,9 +1090,11 @@ static int brcm_pcie_setup(struct brcm_pcie *pcie)
> >  	u32p_replace_bits(&tmp, 1, PCIE_MISC_MISC_CTRL_PCIE_RCB_64B_MODE_MASK);
> >  	writel(tmp, base + PCIE_MISC_MISC_CTRL);
> >  
> > -	num_inbound_wins = brcm_pcie_get_inbound_wins(pcie, inbound_wins);
> > -	if (num_inbound_wins < 0)
> > -		return num_inbound_wins;
> > +	ret = brcm_pcie_get_inbound_wins(pcie, inbound_wins);
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	num_inbound_wins = (u8)ret;
> >  
> >  	set_inbound_win_registers(pcie, inbound_wins, num_inbound_wins);
> >  
> > -- 
> > 2.39.2
> > 

Yes, they have the same effect.

-- 
Best,
Qianqiang Liu

Re: [PATCH] PCI: brcmstb: Fix control flow issue

[Jim Quinlan]

[-- Attachment #1: Type: text/plain, Size: 2099 bytes --]

On Wed, Sep 11, 2024 at 9:56 AM Qianqiang Liu <qianqiang.liu@163.com> wrote:
>
> On Wed, Sep 11, 2024 at 08:44:36AM -0500, Bjorn Helgaas wrote:
> > On Wed, Sep 11, 2024 at 10:50:59AM +0800, Qianqiang Liu wrote:
> > > The type of "num_inbound_wins" is "u8", so the less-than-zero
> > > comparison of an unsigned value is never true.
> >
> > I think this was fixed slightly differently but with the same effect;
> > please check this to make sure:
> >
> > https://git.kernel.org/pub/scm/linux/kernel/git/pci/pci.git/tree/drivers/pci/controller/pcie-brcmstb.c?h=controller/brcmstb#n1034
> >
> > > ---
> > >  drivers/pci/controller/pcie-brcmstb.c | 8 +++++---
> > >  1 file changed, 5 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/drivers/pci/controller/pcie-brcmstb.c b/drivers/pci/controller/pcie-brcmstb.c
> > > index 55311dc47615..3e4572c3eeb1 100644
> > > --- a/drivers/pci/controller/pcie-brcmstb.c
> > > +++ b/drivers/pci/controller/pcie-brcmstb.c
> > > @@ -1090,9 +1090,11 @@ static int brcm_pcie_setup(struct brcm_pcie *pcie)
> > >     u32p_replace_bits(&tmp, 1, PCIE_MISC_MISC_CTRL_PCIE_RCB_64B_MODE_MASK);
> > >     writel(tmp, base + PCIE_MISC_MISC_CTRL);
> > >
> > > -   num_inbound_wins = brcm_pcie_get_inbound_wins(pcie, inbound_wins);
> > > -   if (num_inbound_wins < 0)
> > > -           return num_inbound_wins;
> > > +   ret = brcm_pcie_get_inbound_wins(pcie, inbound_wins);
> > > +   if (ret < 0)
> > > +           return ret;
> > > +
> > > +   num_inbound_wins = (u8)ret;
> > >
> > >     set_inbound_win_registers(pcie, inbound_wins, num_inbound_wins);
> > >
> > > --
> > > 2.39.2
> > >
>
> Yes, they have the same effect.

Qianqiang's fixup has the slight advantage of keeping the var a u8,
which is what a reviewer wanted in the first place.
I found it surprising that  "if (u8var < 0)" does not cause a compiler
warning, but it appears that W=1 does not include "-Wtype-limits".
That's no excuse for this mistake, of course :-(


Thanks and regards,
Jim Quinlan Broadcom STB/CM

>
> --
> Best,
> Qianqiang Liu
>

[-- Attachment #2: S/MIME Cryptographic Signature --]
[-- Type: application/pkcs7-signature, Size: 4210 bytes --]