RE: [PATCH 2/3] drivers: iio: adc: LTC2499 support

From: Regus, Ciprian
Date: Mon Aug 29 2022 - 02:31:10 EST


In reply to one of Andy's questions.

> On Mon, Aug 22, 2022 at 11:13 PM Jonathan Cameron <jic23@xxxxxxxxxx>
> wrote:
> > On Mon, 22 Aug 2022 15:51:05 +0300
> > Ciprian Regus <ciprian.regus@xxxxxxxxxx> wrote:
>
> In reply to Jonathan's comments to answer his question and add more
> comments from me.
>
> ...
>
> > > Datasheet: https://www.analog.com/media/en/technical-
> documentation/data-sheets/2499fe.pdf
> > >
> > > Signed-off-by: Ciprian Regus <ciprian.regus@xxxxxxxxxx>
>
> Tag block mustn't have the blank line(s).
>
> ...
>
> > > #include <linux/iio/iio.h>
> > > #include <linux/iio/driver.h>
> > > #include <linux/module.h>
> > > +#include <linux/property.h>
> > why?
>
> device_get_match_data() requires it.
>
> But why not sort them?
>
> > > #include <linux/mod_devicetable.h>
>
> ...
>
> > > - *val = (be32_to_cpu(st->buf) >> 14) - (1 << 17);
> >
> > Old code here is less than ideal, should be reading into 3 bytes then using
> > the be24 accesors. Please fix whilst here. You will need multiple paths here
> > depending on size.
> >
> > > + *val = (be32_to_cpu(st->buf) >> st->sub_lsb) -
> > > + BIT(ddata->chip_info->resolution + 1);
>
> Shouldn't this use some kind of sign_extend()?
The BIT(ddata->chip_info->resolution + 1) subtraction part is already doing the sign extension,
since that bit (which is the most significant one) will be 0 if the result is < 0, and 1 otherwise.

Regards,
Ciprian
>
> Also with a temporary variable for chip info this line can be single.
>
> struct ... *ci = ddata->chip_info;
>
> ...BIT(ci->resolution + 1)
>
> ...
>
> > > + u32 resolution;
>
> Keep this in a way that the "longer lines go first".
>
> ...
>
> > > + resolution = st->common_ddata.chip_info->resolution;
> > > + st->sub_lsb = 31 - (resolution + 1);
> > > + st->recv_size = resolution / BITS_PER_BYTE + 1;
>
> BITS_TO_BYTES()
>
> ...
>
> > > static const struct i2c_device_id ltc2497_id[] = {
> > > - { "ltc2497", 0 },
> > > + { "ltc2497", TYPE_LTC2497 },
> > > + { "ltc2499", TYPE_LTC2499 },
>
> Use pointers here like you have done for the OF table.
>
> > > { }
> > > };
>
> ...
>
> > > +enum chip_type {
> > > + TYPE_LTC2496,
> > > + TYPE_LTC2497,
> > > + TYPE_LTC2499
>
> Keep trailing comma.
>
> > > +};
>
> --
> With Best Regards,
> Andy Shevchenko