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From:   Andrea Merello <andrea.merello@gmail.com>
Date:   Mon, 19 Jul 2021 12:33:16 +0200
Message-ID: <CAN8YU5MMtP8M7jTDP2S3EBM-PM1dsxVLEgGyB-3BtY5xUF+JTQ@mail.gmail.com>
Subject: Re: [PATCH 2/4] iio: imu: add Bosch Sensortec BNO055 core driver
To:     Andy Shevchenko <andy.shevchenko@gmail.com>
Cc:     Jonathan Cameron <jic23@kernel.org>,
        Lars-Peter Clausen <lars@metafoo.de>,
        Rob Herring <robh+dt@kernel.org>,
        Matt Ranostay <matt.ranostay@konsulko.com>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        linux-iio <linux-iio@vger.kernel.org>,
        Andrea Merello <andrea.merello@iit.it>
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> > > > +               for (i = 0; i < 4; i++)
> > > > +                       vals[i] = (s16)le16_to_cpu(raw_vals[i]);
> > >
> > > Extract this to be a helper like there are for u32 and u64.
> >
> > Could you please point me to those helpers? I don't know what you are
> > referring to.
>
> Read include/linux/byteorder/generic.h to the end.

I realized that implementing an helper like the other ones wouldn't
work in this specific case: I'd say a reasonable helper would take a
ptr to a s16 as its destination argument, but here we are assigning to
a int vector; so our brand new helper would be of no use here.

What I can do is to implement a macroized helper that would have no
issues wrt ptr type; I guess something like this:

#define le16_to_cpu_signed_array(dst, src, len) \
({ \
    size_t __i; \
    for (__i = 0; __i < len; __i++) \
        dst[__i] = (s16)le16_to_cpu(src[__i]); \
})

What's your opinion here? should I go with something like this or do
you prefer to let the open-coded implementation stay in this specific
case?