linux-kernel - Re: [PATCH] drivers: gpu: drm: i915: Replaced calls to kmalloc & memcpy with kmemdup

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Message-ID: <20130311202512.GA7626@jtriplet-mobl1>
Date:	Mon, 11 Mar 2013 13:25:12 -0700
From:	Josh Triplett <josh@...htriplett.org>
To:	Alexandru Gheorghiu <gheorghiuandru@...il.com>
Cc:	Daniel Vetter <daniel.vetter@...ll.ch>,
	David Airlie <airlied@...ux.ie>,
	dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drivers: gpu: drm: i915: Replaced calls to kmalloc &
 memcpy with kmemdup

On Mon, Mar 11, 2013 at 09:30:40PM +0200, Alexandru Gheorghiu wrote:
> Replaced calls to kmalloc followed by memcpy with a single call to kmemdup.
> This patch was found using coccinelle.
> 
> Signed-off-by: Alexandru Gheorghiu <gheorghiuandru@...il.com>
> ---
>  drivers/gpu/drm/i915/intel_dp.c |    3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index f61cb79..a3fdd65 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -2335,11 +2335,10 @@ intel_dp_get_edid(struct drm_connector *connector, struct i2c_adapter *adapter)
>  			return NULL;
>  
>  		size = (intel_connector->edid->extensions + 1) * EDID_LENGTH;
> -		edid = kmalloc(size, GFP_KERNEL);
> +		edid = kmemdup(intel_connector->edid, size, GFP_KERNEL);
>  		if (!edid)
>  			return NULL;
>  
> -		memcpy(edid, intel_connector->edid, size);
>  		return edid;
>  	}

With this change, the conditional no longer makes sense; this should
just "return kmemdup(...);".

That suggests an obvious further cleanup that coccinelle could easily
handle:

if (!foo)
    return NULL;
return foo;

should become just "return foo;".  And you might then want to check for
variables used *only* to capture a return value and immediately
returned, and eliminate them.

- Josh Triplett
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