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Date: Fri, 10 Feb 2017 20:37:38 +0200
From: Sakari Ailus <sakari.ailus@linux.intel.com>
Subject: Re: [PATCH RESEND v7 2/2] Add support for OV5647 sensor.
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To: Ramiro Oliveira <Ramiro.Oliveira@synopsys.com>
Cc: Sakari Ailus <sakari.ailus@iki.fi>, linux-media@vger.kernel.org, linux-kernel@vger.kernel.org, devicetree@vger.kernel.org, CARLOS.PALMINHA@synopsys.com, "David S. Miller" <davem@davemloft.net>, Geert Uytterhoeven <geert+renesas@glider.be>, Greg Kroah-Hartman <gregkh@linuxfoundation.org>, Guenter Roeck <linux@roeck-us.net>, Hans Verkuil <hans.verkuil@cisco.com>, Mark Rutland <mark.rutland@arm.com>, Mauro Carvalho Chehab <mchehab@kernel.org>, Pavel Machek <pavel@ucw.cz>, Robert Jarzmik <robert.jarzmik@free.fr>, Rob Herring <robh+dt@kernel.org>, Steve Longerbeam <slongerbeam@gmail.com>
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Hi Ramiro,

On Thu, Feb 09, 2017 at 10:13:02AM +0000, Ramiro Oliveira wrote:
> Hi Sakari
> 
> On 2/9/2017 10:02 AM, Sakari Ailus wrote:
> > Hi Ramiro,
> > 
> > On Wed, Feb 08, 2017 at 09:56:12AM +0000, Ramiro Oliveira wrote:
> >> Hi Sakari
> >>
> >> On 2/7/2017 5:31 PM, Sakari Ailus wrote:
> >>> Hi Ramiro,
> >>>
> >>> On Mon, Feb 06, 2017 at 11:38:28AM +0000, Ramiro Oliveira wrote:
> >>> ...
> >>>>>> +	ret = ov5647_write_array(sd, ov5647_640x480,
> >>>>>> +					ARRAY_SIZE(ov5647_640x480));
> >>>>>> +	if (ret < 0) {
> >>>>>> +		dev_err(&client->dev, "write sensor_default_regs error\n");
> >>>>>> +		return ret;
> >>>>>> +	}
> >>>>>> +
> >>>>>> +	ov5647_set_virtual_channel(sd, 0);
> >>>>>> +
> >>>>>> +	ov5647_read(sd, 0x0100, &resetval);
> >>>>>> +	if (!(resetval & 0x01)) {
> >>>>>
> >>>>> Can this ever happen? Streaming start is at the end of the register list.
> >>>>>
> >>>>
> >>>> I'm not sure it can happen. It was just a safeguard, but I can remove it if you
> >>>> think it's not necessary
> >>>
> >>> You're not reading back the other registers either, albeit I'd check that
> >>> the I2C accesses actually succeed. Generally the return values are ignored.
> >>>
> >>
> >> So you're recommending I perform a random I2C access after power on to check the
> >> system, and discard the read value? Or just drop this piece of code entirely?
> >>
> > 
> > I'm not. What I'm saying that you're mostly not checking whether I2C
> > accesses succeed or not.
> > 
> 
> 
> I think I'm understanding what you're saying now. You want me to check more
> often the return value from write/read functions?
> 
> That makes sense. I'll add more checks to the code

Please do. That's generally a better approach with I2C than reading back
register values.  :-)

-- 
Sakari Ailus
sakari.ailus@linux.intel.com