2021-02-18 10:48:33

by Muhammad Usama Anjum

Subject: [PATCH] staging: wimax/i2400m: don't change the endianness of one byte variable

It is wrong to change the endianness of a variable which has just one
byte size.

Sparse warnings fixed:
drivers/staging//wimax/i2400m/control.c:452:17: warning: cast to restricted __le32
drivers/staging//wimax/i2400m/control.c:452:17: warning: cast to restricted __le32
drivers/staging//wimax/i2400m/op-rfkill.c:159:14: warning: cast to restricted __le32
drivers/staging//wimax/i2400m/op-rfkill.c:160:14: warning: cast to restricted __le32

Signed-off-by: Muhammad Usama Anjum <[email protected]>
---
drivers/staging/wimax/i2400m/control.c | 4 ++--
drivers/staging/wimax/i2400m/op-rfkill.c | 4 ++--
2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/staging/wimax/i2400m/control.c b/drivers/staging/wimax/i2400m/control.c
index 1e270b2101e8..b6b2788af162 100644
--- a/drivers/staging/wimax/i2400m/control.c
+++ b/drivers/staging/wimax/i2400m/control.c
@@ -452,8 +452,8 @@ void i2400m_report_state_parse_tlv(struct i2400m *i2400m,
d_printf(2, dev, "%s: RF status TLV "
"found (0x%04x), sw 0x%02x hw 0x%02x\n",
tag, I2400M_TLV_RF_STATUS,
- le32_to_cpu(rfss->sw_rf_switch),
- le32_to_cpu(rfss->hw_rf_switch));
+ rfss->sw_rf_switch,
+ rfss->hw_rf_switch);
i2400m_report_tlv_rf_switches_status(i2400m, rfss);
}
if (0 == i2400m_tlv_match(tlv, I2400M_TLV_MEDIA_STATUS, sizeof(*ms))) {
diff --git a/drivers/staging/wimax/i2400m/op-rfkill.c b/drivers/staging/wimax/i2400m/op-rfkill.c
index fbddf2e18c14..a159808f0ec2 100644
--- a/drivers/staging/wimax/i2400m/op-rfkill.c
+++ b/drivers/staging/wimax/i2400m/op-rfkill.c
@@ -156,8 +156,8 @@ void i2400m_report_tlv_rf_switches_status(
enum i2400m_rf_switch_status hw, sw;
enum wimax_st wimax_state;

- sw = le32_to_cpu(rfss->sw_rf_switch);
- hw = le32_to_cpu(rfss->hw_rf_switch);
+ sw = rfss->sw_rf_switch;
+ hw = rfss->hw_rf_switch;

d_fnstart(3, dev, "(i2400m %p rfss %p [hw %u sw %u])\n",
i2400m, rfss, hw, sw);
--
2.25.1

2021-02-18 11:02:19

by Muhammad Usama Anjum

Subject: Re: [PATCH] staging: wimax/i2400m: don't change the endianness of one byte variable

On Thu, 2021-02-18 at 10:40 +0100, Greg KH wrote:
> On Thu, Feb 18, 2021 at 02:21:54PM +0500, Muhammad Usama Anjum wrote:
> > It is wrong to change the endianness of a variable which has just one
> > byte size.
> >
> > Sparse warnings fixed:
> > drivers/staging//wimax/i2400m/control.c:452:17: warning: cast to restricted __le32
> > drivers/staging//wimax/i2400m/control.c:452:17: warning: cast to restricted __le32
> > drivers/staging//wimax/i2400m/op-rfkill.c:159:14: warning: cast to restricted __le32
> > drivers/staging//wimax/i2400m/op-rfkill.c:160:14: warning: cast to restricted __le32
> >
> > Signed-off-by: Muhammad Usama Anjum <[email protected]>
> > ---
> > drivers/staging/wimax/i2400m/control.c | 4 ++--
> > drivers/staging/wimax/i2400m/op-rfkill.c | 4 ++--
> > 2 files changed, 4 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/staging/wimax/i2400m/control.c b/drivers/staging/wimax/i2400m/control.c
> > index 1e270b2101e8..b6b2788af162 100644
> > --- a/drivers/staging/wimax/i2400m/control.c
> > +++ b/drivers/staging/wimax/i2400m/control.c
> > @@ -452,8 +452,8 @@ void i2400m_report_state_parse_tlv(struct i2400m *i2400m,
> > d_printf(2, dev, "%s: RF status TLV "
> > "found (0x%04x), sw 0x%02x hw 0x%02x\n",
> > tag, I2400M_TLV_RF_STATUS,
> > - le32_to_cpu(rfss->sw_rf_switch),
> > - le32_to_cpu(rfss->hw_rf_switch));
> > + rfss->sw_rf_switch,
> > + rfss->hw_rf_switch);
>
> What do you mean by "one byte"? This is a le32 sized variable, right?
> If not, why isn't the le32_to_cpu() call complaining?

These two variables are of type _u8, one byte.
__u8 sw_rf_switch;
__u8 hw_rf_switch;
They aren't of type __le32. le32_to_cpu() macro should have
complained. But it isn't complaining. It seems like whatever we pass
to this macro, it casts it to __le32 forcefully (it seems like wrong).
So we'll never get any complain from this macro directly. But we are
getting complain from the sparse.

For big endian:
#define __le32_to_cpu(x) __swab32((__force __u32)(__le32)(x))
For little endian:
#define __le32_to_cpu(x) ((__force __u32)(__le32)(x))

> > i2400m_report_tlv_rf_switches_status(i2400m, rfss);
> > }
> > if (0 == i2400m_tlv_match(tlv, I2400M_TLV_MEDIA_STATUS, sizeof(*ms))) {
> > diff --git a/drivers/staging/wimax/i2400m/op-rfkill.c b/drivers/staging/wimax/i2400m/op-rfkill.c
> > index fbddf2e18c14..a159808f0ec2 100644
> > --- a/drivers/staging/wimax/i2400m/op-rfkill.c
> > +++ b/drivers/staging/wimax/i2400m/op-rfkill.c
> > @@ -156,8 +156,8 @@ void i2400m_report_tlv_rf_switches_status(
> > enum i2400m_rf_switch_status hw, sw;
> > enum wimax_st wimax_state;
> >
> > - sw = le32_to_cpu(rfss->sw_rf_switch);
> > - hw = le32_to_cpu(rfss->hw_rf_switch);
> > + sw = rfss->sw_rf_switch;
> > + hw = rfss->hw_rf_switch;
>
> Same here.

Same here.

> thanks,
>
> greg k-h

2021-02-18 12:17:22

by Greg KH

Subject: Re: [PATCH] staging: wimax/i2400m: don't change the endianness of one byte variable

On Thu, Feb 18, 2021 at 02:21:54PM +0500, Muhammad Usama Anjum wrote:
> It is wrong to change the endianness of a variable which has just one
> byte size.
>
> Sparse warnings fixed:
> drivers/staging//wimax/i2400m/control.c:452:17: warning: cast to restricted __le32
> drivers/staging//wimax/i2400m/control.c:452:17: warning: cast to restricted __le32
> drivers/staging//wimax/i2400m/op-rfkill.c:159:14: warning: cast to restricted __le32
> drivers/staging//wimax/i2400m/op-rfkill.c:160:14: warning: cast to restricted __le32
>
> Signed-off-by: Muhammad Usama Anjum <[email protected]>
> ---
> drivers/staging/wimax/i2400m/control.c | 4 ++--
> drivers/staging/wimax/i2400m/op-rfkill.c | 4 ++--
> 2 files changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/staging/wimax/i2400m/control.c b/drivers/staging/wimax/i2400m/control.c
> index 1e270b2101e8..b6b2788af162 100644
> --- a/drivers/staging/wimax/i2400m/control.c
> +++ b/drivers/staging/wimax/i2400m/control.c
> @@ -452,8 +452,8 @@ void i2400m_report_state_parse_tlv(struct i2400m *i2400m,
> d_printf(2, dev, "%s: RF status TLV "
> "found (0x%04x), sw 0x%02x hw 0x%02x\n",
> tag, I2400M_TLV_RF_STATUS,
> - le32_to_cpu(rfss->sw_rf_switch),
> - le32_to_cpu(rfss->hw_rf_switch));
> + rfss->sw_rf_switch,
> + rfss->hw_rf_switch);

What do you mean by "one byte"? This is a le32 sized variable, right?
If not, why isn't the le32_to_cpu() call complaining?

> i2400m_report_tlv_rf_switches_status(i2400m, rfss);
> }
> if (0 == i2400m_tlv_match(tlv, I2400M_TLV_MEDIA_STATUS, sizeof(*ms))) {
> diff --git a/drivers/staging/wimax/i2400m/op-rfkill.c b/drivers/staging/wimax/i2400m/op-rfkill.c
> index fbddf2e18c14..a159808f0ec2 100644
> --- a/drivers/staging/wimax/i2400m/op-rfkill.c
> +++ b/drivers/staging/wimax/i2400m/op-rfkill.c
> @@ -156,8 +156,8 @@ void i2400m_report_tlv_rf_switches_status(
> enum i2400m_rf_switch_status hw, sw;
> enum wimax_st wimax_state;
>
> - sw = le32_to_cpu(rfss->sw_rf_switch);
> - hw = le32_to_cpu(rfss->hw_rf_switch);
> + sw = rfss->sw_rf_switch;
> + hw = rfss->hw_rf_switch;

Same here.

thanks,

greg k-h

2021-02-18 19:25:29

by Arnd Bergmann

Subject: Re: [PATCH] staging: wimax/i2400m: don't change the endianness of one byte variable

On Thu, Feb 18, 2021 at 10:54 AM Muhammad Usama Anjum
<[email protected]> wrote:
>
> On Thu, 2021-02-18 at 10:40 +0100, Greg KH wrote:
> > On Thu, Feb 18, 2021 at 02:21:54PM +0500, Muhammad Usama Anjum wrote:
> > > It is wrong to change the endianness of a variable which has just one
> > > byte size.
> > >
> > > Sparse warnings fixed:
> > > drivers/staging//wimax/i2400m/control.c:452:17: warning: cast to restricted __le32
> > > drivers/staging//wimax/i2400m/control.c:452:17: warning: cast to restricted __le32
> > > drivers/staging//wimax/i2400m/op-rfkill.c:159:14: warning: cast to restricted __le32
> > > drivers/staging//wimax/i2400m/op-rfkill.c:160:14: warning: cast to restricted __le32
> > >
> > > Signed-off-by: Muhammad Usama Anjum <[email protected]>
> > > ---
> > > drivers/staging/wimax/i2400m/control.c | 4 ++--
> > > drivers/staging/wimax/i2400m/op-rfkill.c | 4 ++--
> > > 2 files changed, 4 insertions(+), 4 deletions(-)
> > >
> > > diff --git a/drivers/staging/wimax/i2400m/control.c b/drivers/staging/wimax/i2400m/control.c
> > > index 1e270b2101e8..b6b2788af162 100644
> > > --- a/drivers/staging/wimax/i2400m/control.c
> > > +++ b/drivers/staging/wimax/i2400m/control.c
> > > @@ -452,8 +452,8 @@ void i2400m_report_state_parse_tlv(struct i2400m *i2400m,
> > > d_printf(2, dev, "%s: RF status TLV "
> > > "found (0x%04x), sw 0x%02x hw 0x%02x\n",
> > > tag, I2400M_TLV_RF_STATUS,
> > > - le32_to_cpu(rfss->sw_rf_switch),
> > > - le32_to_cpu(rfss->hw_rf_switch));
> > > + rfss->sw_rf_switch,
> > > + rfss->hw_rf_switch);
> >
> > What do you mean by "one byte"? This is a le32 sized variable, right?
> > If not, why isn't the le32_to_cpu() call complaining?
>
> These two variables are of type _u8, one byte.
> __u8 sw_rf_switch;
> __u8 hw_rf_switch;
> They aren't of type __le32. le32_to_cpu() macro should have
> complained. But it isn't complaining. It seems like whatever we pass
> to this macro, it casts it to __le32 forcefully (it seems like wrong).
> So we'll never get any complain from this macro directly. But we are
> getting complain from the sparse.
>
> For big endian:
> #define __le32_to_cpu(x) __swab32((__force __u32)(__le32)(x))
> For little endian:
> #define __le32_to_cpu(x) ((__force __u32)(__le32)(x))

Right, it seems this driver has been broken on big-endian ever since
it was first merged in 2008.

Arnd