linux-kernel - Re: [PATCH v4 1/2] iio: dac: Add AD5758 support

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Date:   Sun, 1 Jul 2018 00:26:56 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Stefan Popa <stefan.popa@...log.com>
Cc:     Jonathan Cameron <jic23@...nel.org>,
        Michael Hennerich <Michael.Hennerich@...log.com>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Hartmut Knaack <knaack.h@....de>,
        Peter Meerwald <pmeerw@...erw.net>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Randy Dunlap <rdunlap@...radead.org>,
        Lukas Wunner <lukas@...ner.de>,
        Ismail.Kose@...imintegrated.com,
        William Breathitt Gray <vilhelm.gray@...il.com>,
        sean.nyekjaer@...vas.dk,
        Philippe Ombredanne <pombredanne@...b.com>,
        linux-iio@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 1/2] iio: dac: Add AD5758 support

On Fri, Jun 29, 2018 at 11:38 AM, Stefan Popa <stefan.popa@...log.com> 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

Thanks for an update.
Few comments below.

> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/spi/spi.h>
> +#include <linux/property.h>
> +#include <linux/delay.h>
> +#include <linux/bsearch.h>

Perhaps keep them ordered?

> +
> +#include <linux/iio/iio.h>
> +#include <linux/iio/sysfs.h>
> +

> +#include <asm/div64.h>

ASM? Hmm...

> +static int cmpfunc(const void *a, const void *b)
> +{
> +       return (*(int *)a - *(int *)b);

Surrounding parens are not needed.

> +}
> +

> +static int ad5758_find_closest_match(const int *array,
> +                                    unsigned int size, int val)
> +{
> +       int i;
> +
> +       for (i = 0; i < size; i++) {
> +               if (val <= array[i])
> +                       return i;
> +       }
> +
> +       return size - 1;
> +}

Isn't it what bsearch() covers as well?

> +       do {
> +               ret = ad5758_spi_reg_read(st, reg);
> +               if (ret < 0)
> +                       return ret;
> +
> +               if (!(ret & mask))
> +                       return 0;
> +

> +               udelay(100);

If it's not called from atomic context, perhaps switch to usleep_range() ?

> +       } while (--timeout);


> +static int ad5758_soft_reset(struct ad5758_state *st)
> +{
> +       int ret;
> +
> +       ret = ad5758_spi_reg_write(st, AD5758_KEY, AD5758_KEY_CODE_RESET_1);
> +       if (ret < 0)
> +               return ret;
> +
> +       ret = ad5758_spi_reg_write(st, AD5758_KEY, AD5758_KEY_CODE_RESET_2);
> +

> +       /* Perform a software reset and wait 100us */
> +       udelay(100);

Ditto.

> +
> +       return ret;
> +}

> +static int ad5758_find_out_range(struct ad5758_state *st,
> +                                const struct ad5758_range *range,
> +                                unsigned int size,
> +                                int min, int max)
> +{
> +       int i;
> +
> +       for (i = 0; i < size; i++) {
> +               if ((min == range[i].min) && (max == range[i].max)) {
> +                       st->out_range.reg = range[i].reg;
> +                       st->out_range.min = range[i].min;
> +                       st->out_range.max = range[i].max;
> +
> +                       return 0;
> +               }
> +       }

One more candidate to use bsearch().

> +
> +       return -EINVAL;
> +}

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

I'm not sure you need that casting.

-- 
With Best Regards,
Andy Shevchenko