linux-kernel - Re: [PATCH] iio: Fix uninitialized symbol 'ret'

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Message-ID: <5f80c1a2-118a-4685-ac1b-81b3479f5064@gmail.com>
Date: Thu, 31 Oct 2024 09:13:16 +0200
From: Matti Vaittinen <mazziesaccount@...il.com>
To: Zicheng Qu <quzicheng@...wei.com>, jic23@...nel.org, lars@...afoo.de,
 linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org
Cc: tanghui20@...wei.com, zhangqiao22@...wei.com, judy.chenhui@...wei.com
Subject: Re: [PATCH] iio: Fix uninitialized symbol 'ret'

Hi Zicheng,

Thanks for the patch.

On 31/10/2024 03:45, Zicheng Qu wrote:
> Initialize the variable ret at the time of declaration to prevent it from
> being returned without a defined value. Fixes smatch warning:
> drivers/iio/industrialio-gts-helper.c:256 gain_to_scaletables() error:
> uninitialized symbol 'ret'.
> 
> Cc: stable@...r.kernel.org # v6.6+
> Fixes: 38416c28e168 ("iio: light: Add gain-time-scale helpers")
> Signed-off-by: Zicheng Qu <quzicheng@...wei.com>
> ---
>   drivers/iio/industrialio-gts-helper.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/iio/industrialio-gts-helper.c b/drivers/iio/industrialio-gts-helper.c
> index 59d7615c0f56..c5dc5b51693d 100644
> --- a/drivers/iio/industrialio-gts-helper.c
> +++ b/drivers/iio/industrialio-gts-helper.c
> @@ -167,7 +167,7 @@ static int iio_gts_gain_cmp(const void *a, const void *b)
>   
>   static int gain_to_scaletables(struct iio_gts *gts, int **gains, int **scales)
>   {
> -	int ret, i, j, new_idx, time_idx;
> +	int i, j, new_idx, time_idx, ret = 0;
>   	int *all_gains;
>   	size_t gain_bytes;
>   

So, if I read it right, this handles a (corner) case where there is no 
times given. I am not sure how well such use has been considered because 
the point of GTS is helping out with cases where the gain and 
integration time both impact to scale.

How do you see the benefits of the gts if there is no such shared impact 
to scale? Sure the gts could still provide the 'standard table format' 
to present the gains (or times), and conversions from the register 
values to gains (or times), and perhaps the available scale table(s) - 
but I suppose it also brings a lot of unused code and some 
initialization overhead. (I have a vague feeling this was discussed with 
Jonathan during the reviews).

Reason I am asking these questions is that I wonder if the usage should 
be limited to cases where we have both gains and times? We could check 
this in the iio_gts_sanity_check(). (And, I am actually a bit surprized 
this check was not implemented).

Well, initialization fixes a potential bug here and does not really cost 
much - so big thanks to you :)

Reviewed-by: Matti Vaittinen <mazziesaccount@...il.com>

Yours,
  -- Matti Vaittinen