linux-kernel - Re: [PATCH] staging: iio: accel: adis16240: Improve readability on write

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Date:   Sun, 11 Aug 2019 09:43:22 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     Rodrigo <rodrigorsdc@...il.com>
Cc:     Lars-Peter Clausen <lars@...afoo.de>,
        Michael Hennerich <Michael.Hennerich@...log.com>,
        Stefan Popa <stefan.popa@...log.com>,
        Hartmut Knaack <knaack.h@....de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-iio@...r.kernel.org, devel@...verdev.osuosl.org,
        linux-kernel@...r.kernel.org, kernel-usp@...glegroups.com
Subject: Re: [PATCH] staging: iio: accel: adis16240: Improve readability on
 write_raw function

On Sat, 10 Aug 2019 12:00:58 -0300
Rodrigo <rodrigorsdc@...il.com> wrote:

> From: Rodrigo Carvalho <rodrigorsdc@...il.com>
> 
> Improve readability by using GENMASK macro, changing switch statement
> by if statement and removing unnecessary local variables.

From your description it sounds like multiple changes in one patch.
Always preferable to have one type of change in a patch and more
small patches.

Based on comments below, I would leave the switch statement alone,
but put in your GENMASK change as that one is good and gets
rid of the odd local variable 'bits' as well :)

Thanks,

Jonathan


> 
> Signed-off-by: Rodrigo Ribeiro Carvalho <rodrigorsdc@...il.com>
> ---
>  drivers/staging/iio/accel/adis16240.c | 16 +++++++---------
>  1 file changed, 7 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/staging/iio/accel/adis16240.c b/drivers/staging/iio/accel/adis16240.c
> index 62f4b3b1b457..68f165501389 100644
> --- a/drivers/staging/iio/accel/adis16240.c
> +++ b/drivers/staging/iio/accel/adis16240.c
> @@ -309,17 +309,15 @@ static int adis16240_write_raw(struct iio_dev *indio_dev,
>  			       long mask)
>  {
>  	struct adis *st = iio_priv(indio_dev);
> -	int bits = 10;
> -	s16 val16;
> +	int m;
>  	u8 addr;
>  
> -	switch (mask) {
> -	case IIO_CHAN_INFO_CALIBBIAS:
> -		val16 = val & ((1 << bits) - 1);
> -		addr = adis16240_addresses[chan->scan_index][0];
> -		return adis_write_reg_16(st, addr, val16);
> -	}
> -	return -EINVAL;
> +	if (mask != IIO_CHAN_INFO_CALIBBIAS)
> +		return -EINVAL;

Hmm. We generally encourage the use of switch statements in these
cases because they reduce churn as new features are added.

In this particular case, we don't have any control of sampling frequency
in the driver, but the hardware appears to support it (table 23 on the
datasheet).


> +
> +	m = GENMASK(9, 0);
> +	addr = adis16240_addresses[chan->scan_index][0];
> +	return adis_write_reg_16(st, addr, val & m);
Why the local variable m?  Can we not just do

	return adis_write_reg_16(st, addr, val & GENMASK(9, 0));

If anything I think that is a little more readable than your
version.  There is a reasonable argument for just having
addr inline as well. 

	return adis_write_reg_16(st,
			         adis16240_addresses[chan->scan_index][0],
				 val & GENMASK(9, 0));

However, given I'm suggesting you leave it as a switch statement, it
will be too long with addr inline.

>  }
>  
>  static const struct iio_chan_spec adis16240_channels[] = {