[PATCH] sound/soc/at32: Useless NULL test

[PATCH] sound/soc/at32: Useless NULL test

[Julien Brunel]

The test (ssc != NULL) can only be reached if the call to the function
ssc_request, the result of which ssc is assigned, succeeds. Moreover,
two statements assign NULL to ssc just before a return, which is useless
since it is a local variable. So, we suggest to delete the test and
the two assignments.

A simplified version of the semantic match that finds this problem is
as follows: 
(http://www.emn.fr/x-info/coccinelle/)

// <smpl>
@bad_null_test@
expression x,E;
@@
x = ssc_request(...)
... when != x = E
* x != NULL
// </smpl>

Signed-off-by:  Julien Brunel <brunel@diku.dk>
Signed-off-by:  Julia Lawall <julia@diku.dk>

---
 sound/soc/at32/playpaq_wm8510.c |    6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff -u -p a/sound/soc/at32/playpaq_wm8510.c b/sound/soc/at32/playpaq_wm8510.c
--- a/sound/soc/at32/playpaq_wm8510.c
+++ b/sound/soc/at32/playpaq_wm8510.c
@@ -405,7 +405,6 @@ static int __init playpaq_asoc_init(void
 	ssc = ssc_request(0);
 	if (IS_ERR(ssc)) {
 		ret = PTR_ERR(ssc);
-		ssc = NULL;
 		goto err_ssc;
 	}
 	ssc_p->ssc = ssc;
@@ -476,10 +475,7 @@ err_pll0:
 		_gclk0 = NULL;
 	}
 err_gclk0:
-	if (ssc != NULL) {
-		ssc_free(ssc);
-		ssc = NULL;
-	}
+	ssc_free(ssc);
 err_ssc:
 	return ret;
 }

Re: [PATCH] sound/soc/at32: Useless NULL test

[Mark Brown]

On Fri, Sep 26, 2008 at 03:23:46PM +0200, Julien Brunel wrote:

> The test (ssc != NULL) can only be reached if the call to the function
> ssc_request, the result of which ssc is assigned, succeeds. Moreover,
> statements assign NULL to ssc just before a return, which is useless
> since it is a local variable. So, we suggest to delete the test and
> the two assignments.

Acked-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

For future reference if you're submitting other similar things (which I
guess you will given that you've got a tool to check for this stuff)
it'd be helpful if you could rewrite the explanation for the NULL test
to be something like:

    The test (ssc != NULL) is redundant since it can only be reached
    when ssc is guaranteed to have been set to a valid ssc.

which is much easier to parse.

> diff -u -p a/sound/soc/at32/playpaq_wm8510.c b/sound/soc/at32/playpaq_wm8510.c
> --- a/sound/soc/at32/playpaq_wm8510.c
> +++ b/sound/soc/at32/playpaq_wm8510.c
> @@ -405,7 +405,6 @@ static int __init playpaq_asoc_init(void
>  	ssc = ssc_request(0);
>  	if (IS_ERR(ssc)) {
>  		ret = PTR_ERR(ssc);
> -		ssc = NULL;
>  		goto err_ssc;
>  	}
>  	ssc_p->ssc = ssc;
> @@ -476,10 +475,7 @@ err_pll0:
>  		_gclk0 = NULL;
>  	}
>  err_gclk0:
> -	if (ssc != NULL) {
> -		ssc_free(ssc);
> -		ssc = NULL;
> -	}
> +	ssc_free(ssc);

Re: [PATCH] sound/soc/at32: Useless NULL test

[Takashi Iwai]

At Fri, 26 Sep 2008 15:00:23 +0100,
Mark Brown wrote:
> 
> On Fri, Sep 26, 2008 at 03:23:46PM +0200, Julien Brunel wrote:
> 
> > The test (ssc != NULL) can only be reached if the call to the function
> > ssc_request, the result of which ssc is assigned, succeeds. Moreover,
> > statements assign NULL to ssc just before a return, which is useless
> > since it is a local variable. So, we suggest to delete the test and
> > the two assignments.
> 
> Acked-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

Applied now.  Thanks.

> For future reference if you're submitting other similar things (which I
> guess you will given that you've got a tool to check for this stuff)
> it'd be helpful if you could rewrite the explanation for the NULL test
> to be something like:
> 
>     The test (ssc != NULL) is redundant since it can only be reached
>     when ssc is guaranteed to have been set to a valid ssc.
> 
> which is much easier to parse.

Agreed :)


Takashi