linux-kernel - Re: [PATCH v2] staging: rtl8188eu: remove dead code/vestigial do..while loop

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Date:   Thu, 26 Sep 2019 12:53:13 -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, dan.carpenter@...cle.com
Cc:     linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: Re: [PATCH v2] staging: rtl8188eu: remove dead code/vestigial
 do..while loop

On 9/24/19 9:28 AM, 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.
> 
> Furthermore, the do..while loop may be removed since it will always only
> execute once because 'bcmd_down' is always set to true, so the
> !bcmd_down evaluates to false and the loop exits immediately after the
> first pass.
> 
> Fix this by removing the loop and its condition variables 'bcmd_down'
> and 'retry_cnts'
> 
> While we're in there, also fix some checkpatch.pl suggestions regarding
> spaces around arithmetic operators like '+'
> 
> Addresses-Coverity: ("Logically dead code")
> 
> Signed-off-by: Connor Kuehl <connor.kuehl@...onical.com>
> ---
> v1 -> v2:
>   - remove the loop and its condition variable bcmd_down
>   - address some non-invasive checkpatch.pl suggestions as a result of
>     deleting the loop
> 
>   drivers/staging/rtl8188eu/hal/rtl8188e_cmd.c | 55 +++++++++-----------
>   1 file changed, 24 insertions(+), 31 deletions(-)
> 
> diff --git a/drivers/staging/rtl8188eu/hal/rtl8188e_cmd.c b/drivers/staging/rtl8188eu/hal/rtl8188e_cmd.c
> index 47352f210c0b..7646167a0b36 100644
> --- a/drivers/staging/rtl8188eu/hal/rtl8188e_cmd.c
> +++ b/drivers/staging/rtl8188eu/hal/rtl8188e_cmd.c
> @@ -47,8 +47,6 @@ 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;
> @@ -71,39 +69,34 @@ static s32 FillH2CCmd_88E(struct adapter *adapt, u8 ElementID, u32 CmdLen, u8 *p
>   		goto exit;
>   
>   	/* pay attention to if  race condition happened in  H2C cmd setting. */
> -	do {
> -		h2c_box_num = adapt->HalData->LastHMEBoxNum;
> -
> -		if (!_is_fw_read_cmd_down(adapt, h2c_box_num)) {
> -			DBG_88E(" fw read cmd failed...\n");
> -			goto exit;
> -		}
> -
> -		*(u8 *)(&h2c_cmd) = ElementID;
> -
> -		if (CmdLen <= 3) {
> -			memcpy((u8 *)(&h2c_cmd)+1, pCmdBuffer, CmdLen);
> -		} else {
> -			memcpy((u8 *)(&h2c_cmd)+1, pCmdBuffer, 3);
> -			ext_cmd_len = CmdLen-3;
> -			memcpy((u8 *)(&h2c_cmd_ex), pCmdBuffer+3, ext_cmd_len);
> +	h2c_box_num = adapt->HalData->LastHMEBoxNum;
>   
> -			/* Write Ext command */
> -			msgbox_ex_addr = REG_HMEBOX_EXT_0 + (h2c_box_num * RTL88E_EX_MESSAGE_BOX_SIZE);
> -			for (cmd_idx = 0; cmd_idx < ext_cmd_len; cmd_idx++)
> -				usb_write8(adapt, msgbox_ex_addr+cmd_idx, *((u8 *)(&h2c_cmd_ex)+cmd_idx));
> -		}
> -		/*  Write command */
> -		msgbox_addr = REG_HMEBOX_0 + (h2c_box_num * RTL88E_MESSAGE_BOX_SIZE);
> -		for (cmd_idx = 0; cmd_idx < RTL88E_MESSAGE_BOX_SIZE; cmd_idx++)
> -			usb_write8(adapt, msgbox_addr+cmd_idx, *((u8 *)(&h2c_cmd)+cmd_idx));
> +	if (!_is_fw_read_cmd_down(adapt, h2c_box_num)) {
> +		DBG_88E(" fw read cmd failed...\n");
> +		goto exit;
> +	}
>   
> -		bcmd_down = true;
> +	*(u8 *)(&h2c_cmd) = ElementID;
>   
> -		adapt->HalData->LastHMEBoxNum =
> -			(h2c_box_num+1) % RTL88E_MAX_H2C_BOX_NUMS;
> +	if (CmdLen <= 3) {
> +		memcpy((u8 *)(&h2c_cmd) + 1, pCmdBuffer, CmdLen);
> +	} else {
> +		memcpy((u8 *)(&h2c_cmd) + 1, pCmdBuffer, 3);
> +		ext_cmd_len = CmdLen - 3;
> +		memcpy((u8 *)(&h2c_cmd_ex), pCmdBuffer + 3, ext_cmd_len);
> +
> +		/* Write Ext command */
> +		msgbox_ex_addr = REG_HMEBOX_EXT_0 + (h2c_box_num * RTL88E_EX_MESSAGE_BOX_SIZE);
> +		for (cmd_idx = 0; cmd_idx < ext_cmd_len; cmd_idx++)
> +			usb_write8(adapt, msgbox_ex_addr + cmd_idx, *((u8 *)(&h2c_cmd_ex) + cmd_idx));
> +	}
> +	/*  Write command */
> +	msgbox_addr = REG_HMEBOX_0 + (h2c_box_num * RTL88E_MESSAGE_BOX_SIZE);
> +	for (cmd_idx = 0; cmd_idx < RTL88E_MESSAGE_BOX_SIZE; cmd_idx++)
> +		usb_write8(adapt, msgbox_addr + cmd_idx, *((u8 *)(&h2c_cmd) + cmd_idx));
>   
> -	} while ((!bcmd_down) && (retry_cnts--));
> +	adapt->HalData->LastHMEBoxNum =
> +		(h2c_box_num + 1) % RTL88E_MAX_H2C_BOX_NUMS;
>   
>   	ret = _SUCCESS;

Acked-by: Larry Finger <Larry.Finger@...inger.net>

Thanks,

Larry