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From:   Andy Shevchenko <andy.shevchenko@gmail.com>
Date:   Thu, 5 May 2022 20:01:22 +0200
Message-ID: <CAHp75VcD-UpG=ppuE2Du2SsQK66MYdrwhXvjHksN5=gqcppYqA@mail.gmail.com>
Subject: Re: [PATCH V3 3/5] iio: accel: sca3300: modified to support multi chips
To:     LI Qingwu <qing-wu.li@leica-geosystems.com.cn>
Cc:     Jonathan Cameron <jic23@kernel.org>,
        Lars-Peter Clausen <lars@metafoo.de>,
        Rob Herring <robh+dt@kernel.org>,
        Tomas Melin <tomas.melin@vaisala.com>,
        devicetree <devicetree@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        linux-iio <linux-iio@vger.kernel.org>,
        Rob Herring <robh@kernel.org>
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On Thu, May 5, 2022 at 4:12 PM LI Qingwu
<qing-wu.li@leica-geosystems.com.cn> wrote:
> > -----Original Message-----
> > From: Andy Shevchenko <andy.shevchenko@gmail.com>
> > Sent: Wednesday, May 4, 2022 10:39 PM
> > On Wed, May 4, 2022 at 4:35 PM LI Qingwu
> > <qing-wu.li@leica-geosystems.com.cn> wrote:
> > > > From: Andy Shevchenko <andy.shevchenko@gmail.com>
> > > > Sent: Wednesday, May 4, 2022 10:20 PM On Wed, May 4, 2022 at 3:36 P=
M
> > > > LI Qingwu <Qing-wu.Li@leica-geosystems.com.cn> wrote:

...

> > > > > +struct sca3300_chip_info {
> > > > > +       const struct iio_chan_spec *channels;
> > > > > +       const int (*accel_scale_table)[2];
> > > > > +       const int *accel_scale_modes_map;
> > > > > +       const unsigned long *scan_masks;
> > > > > +       const int *avail_modes_table;
> > > > > +       const int *freq_modes_map;
> > > > > +       const int *freq_table;
> > > > > +       const u8 num_accel_scales;
> > > > > +       const u8 num_avail_modes;
> > > > > +       const u8 num_channels;
> > > > > +       const u8 num_freqs;
> > > > > +       const u8 chip_id;
> > > >
> > > > Why do you have const qualifier on all members?  The last one is
> > > > understandable, but the rest, esp. pointers should be justified.
> > > Because I thought it was static and has fix value for each chip, unac=
ceptable
> > for you?
> >
> > But why const qualifier? What is the point of it for example for u8 mem=
bers if
> > the entire object is qualified as const below in the same patch?
> >
> > On top of that, please explain what in your opinion the "const ...
> > *foo" gives us, and what we will lose if we remove the "const" part out=
 of them.
>
> Ah, you are right, those const are unnecessary for nonpointer members.
> for the pointers, the contexts that the pointer points to are still writa=
ble.
> what about if I remove all the const from nonpointer and keep it for the =
pointers?
> Like=EF=BC=9A
> const struct iio_chan_spec *channels;
> const int (*accel_scale_table)[2];
> const int (*incli_scale_table)[2];
> const int *accel_scale_modes_map;
> const int *incli_scale_modes_map;
> const unsigned long *scan_masks;
> const int *avail_modes_table;
> const int *freq_modes_map;
> const int *freq_table;
> const char *name;
> u8 num_accel_scales;
> u8 num_incli_scales;
> u8 num_avail_modes;
> u8 num_channels;
> u8 num_freqs;
> u8 chip_id;
> bool angle;

It's better, but you still need to justify the rest with explanation
in the commit message.
And I leave this to maintainers to say if the const:s are needed or not.

> > > > > +       const char *name;
> > > > > +};

--=20
With Best Regards,
Andy Shevchenko