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

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Date:   Thu, 21 Mar 2019 15:28:23 +0100
From:   Tomas Novotny <tomas@...otny.cz>
To:     Angus Ainslie <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 Wed, 20 Mar 2019 13:21:58 -0700
Angus Ainslie <angus@...ea.ca> wrote:

> Hi Tomas,
> 
> On 2019-03-20 07:53, Tomas Novotny wrote:
> > 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.
> >   
> 
> As far as a base address for the register that is correct based on the 
> names in the datasheet. I suppose I could add something like:
> 
> #define VCNL4200_PS_CONF  VCNL4200_PS_CONF1
>
> and change the reference here if you think that would be more clear.

to be honest, I don't know the best practice. As there is also PS_CONF3, I
was thinking about PS_CONF1_2, but thinking again, your current name is good
enough maybe.

Tomas

> >>  	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.  
> 
> Thanks for testing it
> Angus
>