linux-kernel - Re: [PATCH] sbus: Introduce the use of the managed version of kzalloc

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Message-ID: <20140523201703.GA17295@ravnborg.org>
Date:	Fri, 23 May 2014 22:17:03 +0200
From:	Sam Ravnborg <sam@...nborg.org>
To:	Himangi Saraogi <himangi774@...il.com>
Cc:	"David S. Miller" <davem@...emloft.net>,
	sparclinux@...r.kernel.org, linux-kernel@...r.kernel.org,
	julia.lawall@...6.fr
Subject: Re: [PATCH] sbus: Introduce the use of the managed version of kzalloc

Hi Himangi.

On Fri, May 23, 2014 at 02:05:36AM +0530, Himangi Saraogi wrote:
> This patch moves data allocated using kzalloc to managed data allocated
> using devm_kzalloc and cleans now unnecessary kfrees in probe and remove
> functions. The header file is added to make the devm function explicitly
> available. Also, unnecessary assignment statements and labels are
> removed.
> 
> ---
> Not compile tested due to incompatible architecture.
I can confirm that i builds.


> 
> To send to: "David S. Miller" <davem@...emloft.net>,sparclinux@...r.kernel.org,linux-kernel@...r.kernel.org
> 
>  drivers/sbus/char/display7seg.c | 23 ++++++++---------------
>  1 file changed, 8 insertions(+), 15 deletions(-)
> 
> diff --git a/drivers/sbus/char/display7seg.c b/drivers/sbus/char/display7seg.c
> index 7c71e7b..367b64d 100644
> --- a/drivers/sbus/char/display7seg.c
> +++ b/drivers/sbus/char/display7seg.c
> @@ -20,6 +20,7 @@
>  #include <asm/io.h>
>  
>  #include <asm/display7seg.h>
> +#include <linux/device.h>
>  
>  #define D7S_MINOR	193
>  #define DRIVER_NAME	"d7s"
> @@ -173,22 +174,21 @@ static struct miscdevice d7s_miscdev = {
>  static int d7s_probe(struct platform_device *op)
>  {
>  	struct device_node *opts;
> -	int err = -EINVAL;
> +	int err;
>  	struct d7s *p;
>  	u8 regs;
>  
>  	if (d7s_device)
> -		goto out;
> +		return -EINVAL;
>  
> -	p = kzalloc(sizeof(*p), GFP_KERNEL);
> -	err = -ENOMEM;
> +	p = devm_kzalloc(&op->dev, sizeof(*p), GFP_KERNEL);
>  	if (!p)
> -		goto out;
> +		return -ENOMEM;
>  
>  	p->regs = of_ioremap(&op->resource[0], 0, sizeof(u8), "d7s");
>  	if (!p->regs) {
>  		printk(KERN_ERR PFX "Cannot map chip registers\n");
> -		goto out_free;
> +		return -ENOMEM;

Can you please explain how it can be correct to return "-ENOMEM",
when we fail to map the chip registers.
Before your patch this resulted in "-EINVAL" - so this is a change in behaviour.


>  	}
>  
>  	err = misc_register(&d7s_miscdev);
> @@ -222,17 +222,11 @@ static int d7s_probe(struct platform_device *op)
>  
>  	dev_set_drvdata(&op->dev, p);
>  	d7s_device = p;
> -	err = 0;
> -
> -out:
> -	return err;
> +	return 0;
>  
>  out_iounmap:
>  	of_iounmap(&op->resource[0], p->regs, sizeof(u8));
> -
> -out_free:
> -	kfree(p);
> -	goto out;
> +	return err;
>  }
It is not am improvement IMO that you replace the nice goto
based error handling with random return points in the code.

	Sam
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