linux-kernel - Re: First kernel patch (optimization)

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Message-ID: <20150915201148.GU19948@saruman.tx.rr.com>
Date:	Tue, 15 Sep 2015 15:11:48 -0500
From:	Felipe Balbi <balbi@...com>
To:	Eric Curtin <ericcurtin17@...il.com>
CC:	<valentina.manea.m@...il.com>, <shuah.kh@...sung.com>,
	<linux-usb@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: First kernel patch (optimization)

On Tue, Sep 15, 2015 at 08:53:28PM +0100, Eric Curtin wrote:
> My first kernel patch, hope I did everything correctly! Instead of calling strlen on every iteration of the for loop, just call it once instead and store in a variable.

this should be broken up at 72 characters. Also, your subject and commit
log make no sense from a project history perspective. You don't need to
mention it's your first patch, just go straight to the details.

For the subject, I'd use something like:

tools: usbip: detach: avoid calling strlen() at each iteration

and for the commit log:

Instead of calling strlen() on every iterations of the for loop,
just call it once and cache the result in a temporary local variable
which will be used in the for loop instead.

cheers

> Signed-off-by: Eric Curtin <ericcurtin17@...il.com>
> 
> diff --git a/tools/usb/usbip/src/usbip_detach.c b/tools/usb/usbip/src/usbip_detach.c
> index 05c6d15..9db9d21 100644
> --- a/tools/usb/usbip/src/usbip_detach.c
> +++ b/tools/usb/usbip/src/usbip_detach.c
> @@ -47,7 +47,9 @@ static int detach_port(char *port)
>  	uint8_t portnum;
>  	char path[PATH_MAX+1];
>  
> -	for (unsigned int i = 0; i < strlen(port); i++)
> +	unsigned int port_len = strlen(port);
> +
> +	for (unsigned int i = 0; i < port_len; i++)
>  		if (!isdigit(port[i])) {
>  			err("invalid port %s", port);
>  			return -1;
> 
> --
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-- 
balbi

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