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

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Date:   Mon, 18 Jul 2022 11:53:10 +0000 (UTC)
From:   Kalle Valo <kvalo@...nel.org>
To:     Justin Stitt <justinstitt@...gle.com>
Cc:     Jakub Kicinski <kubakici@...pl>,
        "David S . Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Paolo Abeni <pabeni@...hat.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Tom Rix <trix@...hat.com>, linux-wireless@...r.kernel.org,
        netdev@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, linux-kernel@...r.kernel.org,
        llvm@...ts.linux.dev, Justin Stitt <justinstitt@...gle.com>
Subject: Re: wifi: mt7601u: eeprom: fix clang -Wformat warning

Justin Stitt <justinstitt@...gle.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@...gle.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