linux-kernel - Re: [PATCH v3 1/2] iio: dac: Add AD5758 support

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Date:   Fri, 29 Jun 2018 03:18:18 +0530
From:   Himanshu Jha <himanshujha199640@...il.com>
To:     Stefan Popa <stefan.popa@...log.com>
Cc:     jic23@...nel.org, Michael.Hennerich@...log.com, lars@...afoo.de,
        knaack.h@....de, pmeerw@...erw.net, mchehab@...nel.org,
        davem@...emloft.net, gregkh@...uxfoundation.org,
        akpm@...ux-foundation.org, linus.walleij@...aro.org,
        rdunlap@...radead.org, lukas@...ner.de,
        Ismail.Kose@...imintegrated.com, vilhelm.gray@...il.com,
        sean.nyekjaer@...vas.dk, pombredanne@...b.com,
        linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 1/2] iio: dac: Add AD5758 support

On Thu, Jun 28, 2018 at 03:13:32PM +0300, Stefan Popa wrote:
> The AD5758 is a single channel DAC with 16-bit precision which uses the
> SPI interface that operates at clock rates up to 50MHz.
> 
> The output can be configured as voltage or current and is available on a
> single terminal.
> 
> Datasheet:
> http://www.analog.com/media/en/technical-documentation/data-sheets/ad5758.pdf
> 
> Signed-off-by: Stefan Popa <stefan.popa@...log.com>
> ---
[..]
> +static const int ad5758_dc_dc_ilim[6] = {
> +	150000, 200000, 250000, 300000, 350000, 400000
> +};
[..]
> +int cmpfunc(const void *a, const void *b)
> +{
> +	return (*(int *)a - *(int *)b);
> +}

Since Kbuild hit a Sparse error in this function, I would also like to
add that the above implementation of cmpfunc() is not safe.

For eg: https://wandbox.org/permlink/MqGnA3nVg7eAN4I7

The following will be safer:

static int cmpfunc(const void *a, const void *b)
{
	int arg1 = *(const int*)a;
	int arg2 = *(const int*)b;
	return (arg1 > arg2) - (arg1 < arg2);
}

[..]
> +		index = (int *) bsearch(&tmp, ad5758_dc_dc_ilim,
> +					ARRAY_SIZE(ad5758_dc_dc_ilim),
> +					sizeof(int), cmpfunc);

Thanks.
-- 
Himanshu Jha
Undergraduate Student
Department of Electronics & Communication
Guru Tegh Bahadur Institute of Technology