Re: [PATCH v2 1/7] iio: adc: max1027: Add debugfs register read support

From: Jonathan Cameron <jic23@kernel.org>
To: Miquel Raynal <miquel.raynal@bootlin.com>
Cc: Hartmut Knaack <knaack.h@gmx.de>,
	Lars-Peter Clausen <lars@metafoo.de>,
	Peter Meerwald-Stadler <pmeerw@pmeerw.net>,
	Rob Herring <robh+dt@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>, <devicetree@vger.kernel.org>,
	linux-iio@vger.kernel.org, linux-kernel@vger.kernel.org,
	Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Subject: Re: [PATCH v2 1/7] iio: adc: max1027: Add debugfs register read support
Date: Sun, 6 Oct 2019 11:04:24 +0100	[thread overview]
Message-ID: <20191006110424.7781d99d@archlinux> (raw)
In-Reply-To: <20191003173401.16343-2-miquel.raynal@bootlin.com>

On Thu,  3 Oct 2019 19:33:55 +0200
Miquel Raynal <miquel.raynal@bootlin.com> wrote:

> Until now, only write operations were supported. Force two bytes read
> operation when reading from this register (might be wrong when reading
> the temperature, but will work with any other value).

That's worrying as comments go.  Just return an error on the temperature
register if it's going to do the wrong thing.

Thanks,

Jonathan

> 
> Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
> ---
>  drivers/iio/adc/max1027.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/iio/adc/max1027.c b/drivers/iio/adc/max1027.c
> index 214883458582..6cdfe9ef73fc 100644
> --- a/drivers/iio/adc/max1027.c
> +++ b/drivers/iio/adc/max1027.c
> @@ -309,8 +309,11 @@ static int max1027_debugfs_reg_access(struct iio_dev *indio_dev,
>  	struct max1027_state *st = iio_priv(indio_dev);
>  	u8 *val = (u8 *)st->buffer;
>  
> -	if (readval != NULL)
> -		return -EINVAL;
> +	if (readval) {
> +		int ret = spi_read(st->spi, val, 2);
> +		*readval = be16_to_cpu(st->buffer[0]);
> +		return ret;
> +	}
>  
>  	*val = (u8)writeval;
>  	return spi_write(st->spi, val, 1);