linux-kernel - Re: [PATCH] usb: dwc3: debug: remove redundant call to strlen

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Date:   Sun, 09 Feb 2020 19:54:03 +0200
From:   Felipe Balbi <balbi@...nel.org>
To:     Colin King <colin.king@...onical.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-usb@...r.kernel.org
Cc:     kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] usb: dwc3: debug: remove redundant call to strlen

Colin King <colin.king@...onical.com> writes:

> From: Colin Ian King <colin.king@...onical.com>
>
> The call to strlen is redundant since the return value is assigned
> to variable len but not subsequently used. Remove the redundant
> call.
>
> Addresses-Coverity: ("Unused value")
> Signed-off-by: Colin Ian King <colin.king@...onical.com>
> ---
>  drivers/usb/dwc3/debug.h | 2 --
>  1 file changed, 2 deletions(-)
>
> diff --git a/drivers/usb/dwc3/debug.h b/drivers/usb/dwc3/debug.h
> index e56beb9d1e36..ee964352c8e2 100644
> --- a/drivers/usb/dwc3/debug.h
> +++ b/drivers/usb/dwc3/debug.h
> @@ -296,8 +296,6 @@ static inline const char *dwc3_ep_event_string(char *str, size_t size,
>  				status & DEPEVT_STATUS_TRANSFER_ACTIVE ?
>  				" (Active)" : " (Not Active)");
>  
> -		len = strlen(str);
> -

looking at the code here. The problem is elsewhere:

| case DWC3_DEPEVT_XFERNOTREADY:
| 	len = strlen(str);
| 	snprintf(str + len, size - len, "Transfer Not Ready [%d]%s",
| 			event->parameters,
| 			status & DEPEVT_STATUS_TRANSFER_ACTIVE ?
| 			" (Active)" : " (Not Active)");
|
| 	len = strlen(str);
|
| 	/* Control Endpoints */
| 	if (epnum <= 1) {
| 		int phase = DEPEVT_STATUS_CONTROL_PHASE(event->status);
| 		switch (phase) {
| 		case DEPEVT_STATUS_CONTROL_DATA:
| 			snprintf(str + ret, size - ret,
| 					" [Data Phase]");
| 			break;
| 		case DEPEVT_STATUS_CONTROL_STATUS:
| 			snprintf(str + ret, size - ret,
| 					" [Status Phase]");

these two should use str + len and size - len. However, a better fix
would be drop the usage of strlen() and just use the return value from
snprintf().

Do you want to produce that patch, instead? It could be two patches:

	1. replace ret with len in these two cases (a bug fix, possibly
	        Cc stable)
        2. drop usage of strlen() in the entire function (a new feature,
	        for v5.7

-- 
balbi

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