linux-kernel - Re: [PATCH 4/4] igc: drop checksum constant cast to u16 in comparisons

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Message-ID: <20250625171214.5d752668@pumpkin>
Date: Wed, 25 Jun 2025 17:12:14 +0100
From: David Laight <david.laight.linux@...il.com>
To: Simon Horman <horms@...nel.org>
Cc: Jacek Kowalski <jacek@...ekk.info>, Tony Nguyen
 <anthony.l.nguyen@...el.com>, Przemek Kitszel
 <przemyslaw.kitszel@...el.com>, Andrew Lunn <andrew+netdev@...n.ch>, "David
 S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Jakub
 Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
 intel-wired-lan@...ts.osuosl.org, netdev@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/4] igc: drop checksum constant cast to u16 in
 comparisons

On Wed, 25 Jun 2025 13:22:39 +0100
Simon Horman <horms@...nel.org> wrote:

> On Tue, Jun 24, 2025 at 09:31:08PM +0200, Jacek Kowalski wrote:
> > Signed-off-by: Jacek Kowalski <Jacek@...ekk.info>
> > Suggested-by: Simon Horman <horms@...nel.org>
> > ---
> >  drivers/net/ethernet/intel/igc/igc_nvm.c | 2 +-  
> 
> I think we should add this:
> 
> diff --git a/drivers/net/ethernet/intel/igc/igc_nvm.c b/drivers/net/ethernet/intel/igc/igc_nvm.c
> index c4fb35071636..a47b8d39238c 100644
> --- a/drivers/net/ethernet/intel/igc/igc_nvm.c
> +++ b/drivers/net/ethernet/intel/igc/igc_nvm.c
> @@ -155,7 +155,7 @@ s32 igc_update_nvm_checksum(struct igc_hw *hw)
>  		}
>  		checksum += nvm_data;
>  	}
> -	checksum = (u16)NVM_SUM - checksum;
> +	checksum = NVM_SUM - checksum;

Indeed - especially as the '-' code is really:
	checksum = (int)(u16)NVM_SUM - checksum;

  David

>  	ret_val = hw->nvm.ops.write(hw, NVM_CHECKSUM_REG, 1, &checksum);
>  	if (ret_val)
>  		hw_dbg("NVM Write Error while updating checksum.\n");
>