linux-kernel - Re: [PATCH v2 1/5] iio: light: vcnl4000 use word writes instead of byte writes

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Date:   Wed, 20 Mar 2019 15:53:22 +0100
From:   Tomas Novotny <tomas@...otny.cz>
To:     "Angus Ainslie (Purism)" <angus@...ea.ca>
Cc:     Jonathan Cameron <jic23@...nel.org>,
        Hartmut Knaack <knaack.h@....de>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>, linux-iio@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/5] iio: light: vcnl4000 use word writes instead of
 byte writes

Hi Angus,

On Sun, 17 Mar 2019 08:47:58 -0700
"Angus Ainslie (Purism)" <angus@...ea.ca> wrote:

> The VCNL4200 datasheet says that word read and writes should be used
> to access the registers.
> 
> Signed-off-by: Angus Ainslie (Purism) <angus@...ea.ca>
> ---
>  drivers/iio/light/vcnl4000.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/iio/light/vcnl4000.c b/drivers/iio/light/vcnl4000.c
> index 04fd0d4b6f19..5295330b65e2 100644
> --- a/drivers/iio/light/vcnl4000.c
> +++ b/drivers/iio/light/vcnl4000.c
> @@ -140,10 +140,10 @@ static int vcnl4200_init(struct vcnl4000_data *data)
>  	data->rev = (ret >> 8) & 0xf;
>  
>  	/* Set defaults and enable both channels */
> -	ret = i2c_smbus_write_byte_data(data->client, VCNL4200_AL_CONF, 0x00);
> +	ret = i2c_smbus_write_word_data(data->client, VCNL4200_AL_CONF, 0x00);

minor note: the 0x00 looks like a byte. 0 or 0x0000 would be slightly better?
The same below.

>  	if (ret < 0)
>  		return ret;
> -	ret = i2c_smbus_write_byte_data(data->client, VCNL4200_PS_CONF1, 0x00);
> +	ret = i2c_smbus_write_word_data(data->client, VCNL4200_PS_CONF1, 0x00);

The VCNL4200_PS_CONF1 definition is a bit misleading with word write. Because
PS_CONF1 is only a low byte of command code 0x03. The high byte of 0x03 is
PS_CONF2. I would rename it.

>  	if (ret < 0)
>  		return ret;

Anyway, the main point is that I've tested this patch on VCNL4200 and it
works, so:
Tested-by: Tomas Novotny <tomas@...otny.cz>

T.