linux-kernel - RE: [PATCH] staging: rtl8192e: Use min_t/max

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Date:   Thu, 3 Nov 2022 08:24:15 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Deepak R Varma' <drv@...lo.com>,
        "outreachy@...ts.linux.dev" <outreachy@...ts.linux.dev>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "linux-staging@...ts.linux.dev" <linux-staging@...ts.linux.dev>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] staging: rtl8192e: Use min_t/max_t macros for variable
 comparison

From: Deepak R Varma
> Sent: 02 November 2022 22:37
> 
> Simplify code by using min_t and max_t helper macros in place of lengthy
> if/else block oriented logical evaluation and value assignment. This
> issue is identified by coccicheck using the minmax.cocci file.
> 
> Use the *_t variants of min/max macros to avoid compiler warnings about
> data typecast.
> Also, use u32 as type for min_t macro to avoid any truncation of data
> associated with enum constant HT_AGG_SIZE_32K.
> 
> Signed-off-by: Deepak R Varma <drv@...lo.com>
> ---
>  drivers/staging/rtl8192e/rtl819x_HTProc.c | 13 ++++---------
>  1 file changed, 4 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/staging/rtl8192e/rtl819x_HTProc.c b/drivers/staging/rtl8192e/rtl819x_HTProc.c
> index 62aa8e893c34..ccb86660ab48 100644
> --- a/drivers/staging/rtl8192e/rtl819x_HTProc.c
> +++ b/drivers/staging/rtl8192e/rtl819x_HTProc.c
> @@ -587,17 +587,12 @@ void HTOnAssocRsp(struct rtllib_device *ieee)
>  			else
>  				pHTInfo->CurrentAMPDUFactor = HT_AGG_SIZE_64K;
>  		} else {
> -			if (pPeerHTCap->MaxRxAMPDUFactor < HT_AGG_SIZE_32K)
> -				pHTInfo->CurrentAMPDUFactor =
> -						 pPeerHTCap->MaxRxAMPDUFactor;
> -			else
> -				pHTInfo->CurrentAMPDUFactor = HT_AGG_SIZE_32K;
> +			pHTInfo->CurrentAMPDUFactor = min_t(u32, pPeerHTCap->MaxRxAMPDUFactor,
> +							    HT_AGG_SIZE_32K);

For min() to fail there must be a signed v unsigned mismatch.
Maybe that ought to be fixed.

>  		}
>  	}
> -	if (pHTInfo->MPDU_Density > pPeerHTCap->MPDUDensity)
> -		pHTInfo->current_mpdu_density = pHTInfo->MPDU_Density;
> -	else
> -		pHTInfo->current_mpdu_density = pPeerHTCap->MPDUDensity;
> +	pHTInfo->current_mpdu_density = max_t(u8, pHTInfo->MPDU_Density,
> +					      pPeerHTCap->MPDUDensity);

Using u8 with max_t() really doesn't make any sense.
The value will get promoted to signed int prior to the comparison.

	David

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