linux-kernel - Re: [PATCH] staging: rtl8188eu: remove dead code in do-while conditional step

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Message-ID: <c2ce3fb0-6407-982a-a3f2-172cef17f2a6@lwfinger.net>
Date:   Mon, 23 Sep 2019 15:38:39 -0500
From:   Larry Finger <Larry.Finger@...inger.net>
To:     Connor Kuehl <connor.kuehl@...onical.com>,
        gregkh@...uxfoundation.org, straube.linux@...il.com,
        devel@...verdev.osuosl.org
Cc:     linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: Re: [PATCH] staging: rtl8188eu: remove dead code in do-while
 conditional step

On 9/23/19 2:48 PM, Connor Kuehl wrote:
> The local variable 'bcmd_down' is always set to true almost immediately
> before the do-while's condition is checked. As a result, !bcmd_down
> evaluates to false which short circuits the logical AND operator meaning
> that the second operand is never reached and is therefore dead code.
> 
> Addresses-Coverity: ("Logically dead code")
> 
> Signed-off-by: Connor Kuehl <connor.kuehl@...onical.com>
> ---
>   drivers/staging/rtl8188eu/hal/rtl8188e_cmd.c | 3 +--
>   1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/drivers/staging/rtl8188eu/hal/rtl8188e_cmd.c b/drivers/staging/rtl8188eu/hal/rtl8188e_cmd.c
> index 47352f210c0b..a4b317937b23 100644
> --- a/drivers/staging/rtl8188eu/hal/rtl8188e_cmd.c
> +++ b/drivers/staging/rtl8188eu/hal/rtl8188e_cmd.c
> @@ -48,7 +48,6 @@ static u8 _is_fw_read_cmd_down(struct adapter *adapt, u8 msgbox_num)
>   static s32 FillH2CCmd_88E(struct adapter *adapt, u8 ElementID, u32 CmdLen, u8 *pCmdBuffer)
>   {
>   	u8 bcmd_down = false;
> -	s32 retry_cnts = 100;
>   	u8 h2c_box_num;
>   	u32 msgbox_addr;
>   	u32 msgbox_ex_addr;
> @@ -103,7 +102,7 @@ static s32 FillH2CCmd_88E(struct adapter *adapt, u8 ElementID, u32 CmdLen, u8 *p
>   		adapt->HalData->LastHMEBoxNum =
>   			(h2c_box_num+1) % RTL88E_MAX_H2C_BOX_NUMS;
>   
> -	} while ((!bcmd_down) && (retry_cnts--));
> +	} while (!bcmd_down);
>   
>   	ret = _SUCCESS;

This patch is correct; however, the do..while loop will always be executed once, 
thus you could remove the loop and the loop variable bcmd_down.

@greg: If you would prefer a two-step process, then this one is OK.

Larry