[PATCH] mediatek: mt76: eeprom: fix clang -Wformat warning

[PATCH] mediatek: mt76: eeprom: fix clang -Wformat warning

[Justin Stitt]

When building with Clang we encounter the following warning:
| drivers/net/wireless/mediatek/mt7601u/eeprom.c:193:5: error: format
| specifies type 'char' but the argument has type 'int' [-Werror,-Wformat]
| chan_bounds[idx].start + chan_bounds[idx].num - 1);

Variadic functions (printf-like) undergo default argument promotion.
Documentation/core-api/printk-formats.rst specifically recommends using
the promoted-to-type's format flag.

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.`

With this information in hand, we really should stop using `%hh[dxu]` or
`%h[dxu]` as they usually prompt Clang -Wformat warnings as well as go
against documented standard recommendations.

Link: https://github.com/ClangBuiltLinux/linux/issues/378
Signed-off-by: Justin Stitt <justinstitt@google.com>
---
Note: produced warning with x86 allyesconfig.

 drivers/net/wireless/mediatek/mt7601u/eeprom.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/wireless/mediatek/mt7601u/eeprom.c b/drivers/net/wireless/mediatek/mt7601u/eeprom.c
index aa3b64902cf9..625bebe60538 100644
--- a/drivers/net/wireless/mediatek/mt7601u/eeprom.c
+++ b/drivers/net/wireless/mediatek/mt7601u/eeprom.c
@@ -188,7 +188,7 @@ mt7601u_set_country_reg(struct mt7601u_dev *dev, u8 *eeprom)
 
 	if (idx != -1)
 		dev_info(dev->dev,
-			 "EEPROM country region %02hhx (channels %hhd-%hhd)\n",
+			 "EEPROM country region %02x (channels %d-%d)\n",
 			 val, chan_bounds[idx].start,
 			 chan_bounds[idx].start + chan_bounds[idx].num - 1);
 	else
-- 
2.37.0.rc0.161.g10f37bed90-goog

Re: wifi: mt7601u: eeprom: fix clang -Wformat warning

[Kalle Valo]

Justin Stitt <justinstitt@google.com> wrote:

> When building with Clang we encounter the following warning:
> | drivers/net/wireless/mediatek/mt7601u/eeprom.c:193:5: error: format
> | specifies type 'char' but the argument has type 'int' [-Werror,-Wformat]
> | chan_bounds[idx].start + chan_bounds[idx].num - 1);
> 
> Variadic functions (printf-like) undergo default argument promotion.
> Documentation/core-api/printk-formats.rst specifically recommends using
> the promoted-to-type's format flag.
> 
> 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.`
> 
> With this information in hand, we really should stop using `%hh[dxu]` or
> `%h[dxu]` as they usually prompt Clang -Wformat warnings as well as go
> against documented standard recommendations.
> 
> Link: https://github.com/ClangBuiltLinux/linux/issues/378
> Signed-off-by: Justin Stitt <justinstitt@google.com>

Patch applied to wireless-next.git, thanks.

07db88f11e63 wifi: mt7601u: eeprom: fix clang -Wformat warning

-- 
https://patchwork.kernel.org/project/linux-wireless/patch/20220709001527.618593-1-justinstitt@google.com/

https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches