linux-kernel - Re: [PATCH] divide by 3*sizeof(u32) when computing array

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Message-ID: <e597d6b8-55d6-2fa6-5f79-86ff813d8bd2@pmhahn.de>
Date:   Tue, 13 Jul 2021 08:02:26 +0200
From:   Philipp Hahn <pmhahn@...ahn.de>
To:     Salah Triki <salah.triki@...il.com>, fabrice.gasnier@...s.st.com,
        thierry.reding@...il.com, u.kleine-koenig@...gutronix.de,
        lee.jones@...aro.org, mcoquelin.stm32@...il.com,
        alexandre.torgue@...s.st.com
Cc:     linux-pwm@...r.kernel.org,
        linux-stm32@...md-mailman.stormreply.com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] divide by 3*sizeof(u32) when computing array_size

Hello,

Disclaimer: I have no idea what 'pwm-stm32' is or does

Am 13.07.21 um 01:19 schrieb Salah Triki:
> Divide by 3*sizeof(u32) when computing array_size, since stm32_breakinput
> has 3 fields of type u32.
...
> --- a/drivers/pwm/pwm-stm32.c
> +++ b/drivers/pwm/pwm-stm32.c
> @@ -544,7 +544,7 @@ static int stm32_pwm_probe_breakinputs(struct stm32_pwm *priv,
>   		return -EINVAL;
>   
>   	priv->num_breakinputs = nb;
> -	array_size = nb * sizeof(struct stm32_breakinput) / sizeof(u32);
> +	array_size = nb * sizeof(struct stm32_breakinput) / (3 * sizeof(u32));

Maybe it's too early in the morning for me, but this does not look right:

> struct stm32_breakinput {
> 	u32 index;
> 	u32 level;
> 	u32 filter;
> };

then "sizeof(struct stm32_breakinput)" == "(3 * sizeof(u32))", which 
would simply make "arrray_site := nb" ?

Philipp