[PATCH] amd-xgbe: fix clang -Wformat warnings

[PATCH] amd-xgbe: fix clang -Wformat warnings

[Justin Stitt]

When building with Clang we encounter the following warning:
| drivers/net/ethernet/amd/xgbe/xgbe-dcb.c:234:42: error: format specifies
| type 'unsigned char' but the argument has type '__u16' (aka 'unsigned
| short') [-Werror,-Wformat] pfc->pfc_cap, pfc->pfc_en, pfc->mbc,
| pfc->delay);

pfc->pfc_cap , pfc->pfc_cn, pfc->mbc are all of type `u8` while pfc->delay is
of type `u16`. The correct format specifiers `%hh[u|x]` were used for
the first three but not for pfc->delay, which is causing the warning
above.

Variadic functions (printf-like) undergo default argument promotion.
Documentation/core-api/printk-formats.rst specifically recommends using
the promoted-to-type's format flag. In this case `%d` (or `%x` to
maintain hex representation) should be used since both u8's and u16's
are fully representable by an int.

Moreover, C11 6.3.1.1 states:
(https://www.open-std.org/jtc1/sc22/wg14/www/docs/n1548.pdf) `If an int
can represent all values of the original type ..., the value is
converted to an int; otherwise, it is converted to an unsigned int.
These are called the integer promotions.`

Link: https://github.com/ClangBuiltLinux/linux/issues/378
Signed-off-by: Justin Stitt <justinstitt@google.com>
---
For clarification, the first three parameters given to netif_dbg did NOT
cause a -Wformat warning. I changed them simply to follow what the
standard and documentation recommend.

 drivers/net/ethernet/amd/xgbe/xgbe-dcb.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/amd/xgbe/xgbe-dcb.c b/drivers/net/ethernet/amd/xgbe/xgbe-dcb.c
index 895d35639129..c68ace804e37 100644
--- a/drivers/net/ethernet/amd/xgbe/xgbe-dcb.c
+++ b/drivers/net/ethernet/amd/xgbe/xgbe-dcb.c
@@ -230,7 +230,7 @@ static int xgbe_dcb_ieee_setpfc(struct net_device *netdev,
 	struct xgbe_prv_data *pdata = netdev_priv(netdev);
 
 	netif_dbg(pdata, drv, netdev,
-		  "cap=%hhu, en=%#hhx, mbc=%hhu, delay=%hhu\n",
+		  "cap=%d, en=%#x, mbc=%d, delay=%d\n",
 		  pfc->pfc_cap, pfc->pfc_en, pfc->mbc, pfc->delay);
 
 	/* Check PFC for supported number of traffic classes */
-- 
2.37.0.rc0.161.g10f37bed90-goog

Re: [PATCH] amd-xgbe: fix clang -Wformat warnings

[Nick Desaulniers]

On Fri, Jul 8, 2022 at 4:27 PM Justin Stitt <justinstitt@google.com> wrote:
>
> When building with Clang we encounter the following warning:
> | drivers/net/ethernet/amd/xgbe/xgbe-dcb.c:234:42: error: format specifies
> | type 'unsigned char' but the argument has type '__u16' (aka 'unsigned
> | short') [-Werror,-Wformat] pfc->pfc_cap, pfc->pfc_en, pfc->mbc,
> | pfc->delay);
>
> pfc->pfc_cap , pfc->pfc_cn, pfc->mbc are all of type `u8` while pfc->delay is
> of type `u16`. The correct format specifiers `%hh[u|x]` were used for
> the first three but not for pfc->delay, which is causing the warning
> above.
>
> Variadic functions (printf-like) undergo default argument promotion.
> Documentation/core-api/printk-formats.rst specifically recommends using
> the promoted-to-type's format flag. In this case `%d` (or `%x` to
> maintain hex representation) should be used since both u8's and u16's
> are fully representable by an int.
>
> Moreover, C11 6.3.1.1 states:
> (https://www.open-std.org/jtc1/sc22/wg14/www/docs/n1548.pdf) `If an int
> can represent all values of the original type ..., the value is
> converted to an int; otherwise, it is converted to an unsigned int.
> These are called the integer promotions.`
>
> Link: https://github.com/ClangBuiltLinux/linux/issues/378
> Signed-off-by: Justin Stitt <justinstitt@google.com>

Thanks for the patch, this fixes an instance of -Wformat I observe for
x86_64 allmodconfig.  I thought you had already fixed this file up?
https://lore.kernel.org/llvm/20220607191119.20686-1-jstitt007@gmail.com/
which was merged. I'm guessing that was from a defconfig, while this
was from an allmodconfig?
Seems like there's a bunch of config ifdef'ery around the definition
of netif_dbg.

Either way, thanks for the patches and

Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>

> ---
> For clarification, the first three parameters given to netif_dbg did NOT
> cause a -Wformat warning. I changed them simply to follow what the
> standard and documentation recommend.
>
>  drivers/net/ethernet/amd/xgbe/xgbe-dcb.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/net/ethernet/amd/xgbe/xgbe-dcb.c b/drivers/net/ethernet/amd/xgbe/xgbe-dcb.c
> index 895d35639129..c68ace804e37 100644
> --- a/drivers/net/ethernet/amd/xgbe/xgbe-dcb.c
> +++ b/drivers/net/ethernet/amd/xgbe/xgbe-dcb.c
> @@ -230,7 +230,7 @@ static int xgbe_dcb_ieee_setpfc(struct net_device *netdev,
>         struct xgbe_prv_data *pdata = netdev_priv(netdev);
>
>         netif_dbg(pdata, drv, netdev,
> -                 "cap=%hhu, en=%#hhx, mbc=%hhu, delay=%hhu\n",
> +                 "cap=%d, en=%#x, mbc=%d, delay=%d\n",
>                   pfc->pfc_cap, pfc->pfc_en, pfc->mbc, pfc->delay);
>
>         /* Check PFC for supported number of traffic classes */
> --
> 2.37.0.rc0.161.g10f37bed90-goog
>


-- 
Thanks,
~Nick Desaulniers

Re: [PATCH] amd-xgbe: fix clang -Wformat warnings

[Justin Stitt]

On Fri, Jul 8, 2022 at 4:48 PM Nick Desaulniers <ndesaulniers@google.com> wrote:
>
> On Fri, Jul 8, 2022 at 4:27 PM Justin Stitt <justinstitt@google.com> wrote:
> >
> > When building with Clang we encounter the following warning:
> > | drivers/net/ethernet/amd/xgbe/xgbe-dcb.c:234:42: error: format specifies
> > | type 'unsigned char' but the argument has type '__u16' (aka 'unsigned
> > | short') [-Werror,-Wformat] pfc->pfc_cap, pfc->pfc_en, pfc->mbc,
> > | pfc->delay);
> >
> > pfc->pfc_cap , pfc->pfc_cn, pfc->mbc are all of type `u8` while pfc->delay is
> > of type `u16`. The correct format specifiers `%hh[u|x]` were used for
> > the first three but not for pfc->delay, which is causing the warning
> > above.
> >
> > Variadic functions (printf-like) undergo default argument promotion.
> > Documentation/core-api/printk-formats.rst specifically recommends using
> > the promoted-to-type's format flag. In this case `%d` (or `%x` to
> > maintain hex representation) should be used since both u8's and u16's
> > are fully representable by an int.
> >
> > Moreover, C11 6.3.1.1 states:
> > (https://www.open-std.org/jtc1/sc22/wg14/www/docs/n1548.pdf) `If an int
> > can represent all values of the original type ..., the value is
> > converted to an int; otherwise, it is converted to an unsigned int.
> > These are called the integer promotions.`
> >
> > Link: https://github.com/ClangBuiltLinux/linux/issues/378
> > Signed-off-by: Justin Stitt <justinstitt@google.com>
>
> Thanks for the patch, this fixes an instance of -Wformat I observe for
> x86_64 allmodconfig.  I thought you had already fixed this file up?
> https://lore.kernel.org/llvm/20220607191119.20686-1-jstitt007@gmail.com/
> which was merged. I'm guessing that was from a defconfig, while this
> was from an allmodconfig?
> Seems like there's a bunch of config ifdef'ery around the definition
> of netif_dbg.

Definitely different across configs but ALSO files are
ever-so-slightly different:
amd/xgbe/xgbe-drv.c      _v.s_      amd/xgbe/xgbe-dcb.c

>
> Either way, thanks for the patches and
>
> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
> Tested-by: Nick Desaulniers <ndesaulniers@google.com>
>
> > ---
> > For clarification, the first three parameters given to netif_dbg did NOT
> > cause a -Wformat warning. I changed them simply to follow what the
> > standard and documentation recommend.
> >
> >  drivers/net/ethernet/amd/xgbe/xgbe-dcb.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/net/ethernet/amd/xgbe/xgbe-dcb.c b/drivers/net/ethernet/amd/xgbe/xgbe-dcb.c
> > index 895d35639129..c68ace804e37 100644
> > --- a/drivers/net/ethernet/amd/xgbe/xgbe-dcb.c
> > +++ b/drivers/net/ethernet/amd/xgbe/xgbe-dcb.c
> > @@ -230,7 +230,7 @@ static int xgbe_dcb_ieee_setpfc(struct net_device *netdev,
> >         struct xgbe_prv_data *pdata = netdev_priv(netdev);
> >
> >         netif_dbg(pdata, drv, netdev,
> > -                 "cap=%hhu, en=%#hhx, mbc=%hhu, delay=%hhu\n",
> > +                 "cap=%d, en=%#x, mbc=%d, delay=%d\n",
> >                   pfc->pfc_cap, pfc->pfc_en, pfc->mbc, pfc->delay);
> >
> >         /* Check PFC for supported number of traffic classes */
> > --
> > 2.37.0.rc0.161.g10f37bed90-goog
> >
>
>
> --
> Thanks,
> ~Nick Desaulniers

Re: [PATCH] amd-xgbe: fix clang -Wformat warnings

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net-next.git (master)
by Jakub Kicinski <kuba@kernel.org>:

On Fri,  8 Jul 2022 16:26:53 -0700 you wrote:
> When building with Clang we encounter the following warning:
> | drivers/net/ethernet/amd/xgbe/xgbe-dcb.c:234:42: error: format specifies
> | type 'unsigned char' but the argument has type '__u16' (aka 'unsigned
> | short') [-Werror,-Wformat] pfc->pfc_cap, pfc->pfc_en, pfc->mbc,
> | pfc->delay);
> 
> pfc->pfc_cap , pfc->pfc_cn, pfc->mbc are all of type `u8` while pfc->delay is
> of type `u16`. The correct format specifiers `%hh[u|x]` were used for
> the first three but not for pfc->delay, which is causing the warning
> above.
> 
> [...]

Here is the summary with links:
  - amd-xgbe: fix clang -Wformat warnings
    https://git.kernel.org/netdev/net-next/c/2afe46474ba3

You are awesome, thank you!
-- 
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