Re: [PATCH v2 1/2] dt-bindings: media: i2c: Add Samsung S5KJN1 image sensor

[Sakari Ailus <sakari.ailus@linux.intel.com>]

Hi Vladimir,

On Tue, Oct 21, 2025 at 01:23:31PM +0300, Vladimir Zapolskiy wrote:
> On 10/21/25 12:10, Sakari Ailus wrote:
> > Hi Vladimir,
> > 
> > On Tue, Oct 21, 2025 at 11:00:35AM +0300, Vladimir Zapolskiy wrote:
> > > Hi Sakari.
> > > 
> > > On 10/20/25 23:23, Sakari Ailus wrote:
> > > > Hi Vladimir,
> > > > 
> > > > Thanks for the set.
> > > > 
> > > > On Thu, Oct 16, 2025 at 05:04:18AM +0300, Vladimir Zapolskiy wrote:
> > > > > Add device tree bindings documentation for Samsung S5KJN1 image sensor.
> > > > > 
> > > > > Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
> > > > > Signed-off-by: Vladimir Zapolskiy <vladimir.zapolskiy@linaro.org>
> > > > > ---
> > > > >    .../bindings/media/i2c/samsung,s5kjn1.yaml    | 95 +++++++++++++++++++
> > > > >    1 file changed, 95 insertions(+)
> > > > >    create mode 100644 Documentation/devicetree/bindings/media/i2c/samsung,s5kjn1.yaml
> > > > > 
> > > > > diff --git a/Documentation/devicetree/bindings/media/i2c/samsung,s5kjn1.yaml b/Documentation/devicetree/bindings/media/i2c/samsung,s5kjn1.yaml
> > > > > new file mode 100644
> > > > > index 000000000000..2220b3e528d4
> > > > > --- /dev/null
> > > > > +++ b/Documentation/devicetree/bindings/media/i2c/samsung,s5kjn1.yaml
> > > > > @@ -0,0 +1,95 @@
> > > > > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > > > > +%YAML 1.2
> > > > > +---
> > > > > +$id: http://devicetree.org/schemas/media/i2c/samsung,s5kjn1.yaml#
> > > > > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > > > > +
> > > > > +title: Samsung S5KJN1 Image Sensor
> > > > > +
> > > > > +description:
> > > > > +  Samsung S5KJN1 (ISOCELL JN1) image sensor is a 50MP image sensor.
> > > > > +  The sensor is controlled over a serial camera control bus protocol,
> > > > > +  the widest supported output image frame size is 8160x6144 at 10 frames
> > > > > +  per second rate, data output format is RAW10 transferred over 4-lane
> > > > > +  MIPI D-PHY interface.
> > > > 
> > > > Can the sensor work with fewer lanes? This is almost always the case. In
> > > > this case you'd need data-lanes property but feel free to make 4 the
> > > > default if you like.
> > > 
> > > As usual I don't have access to the sensor datasheet, what is known to me
> > > is that
> > > 
> > > 1) there is no examples in the downstream, when MIPI CSI interface is
> > > configured in any other mode but 4 lanes D-PHY RAW10,
> > > 
> > > 2) right the same information is given in the official scarce booklet:
> > > 
> > > https://semiconductor.samsung.com/image-sensor/mobile-image-sensor/isocell-jn1/
> > > 
> > > The same reasoning as above is directly applicable to the second sent
> > > sensor driver of Samsung S5K3M5.
> > > 
> > > There is a known practical pattern that if it happens to be of necessity
> > > any new properties can be added to device's dt bindings later on, thus
> > > it should be safe to omit any presumably non-configurable hardware
> > > properties from the description on an early stage.
> > 
> > Even if the driver supports four lanes only, it's very unlikely the sensor
> 
> Well, the second point given above is not about the driver, but it leads
> to the shortest possible sensor hardware spec:
> 
> https://semiconductor.samsung.com/image-sensor/mobile-image-sensor/isocell-jn1/
> 
> If you scroll right to the bottom, it says
> 
> Interface: 4 lanes (2.15 Gbps per lane)
> 
> It does not completely or clearly exclude 1 or 2 lane configuration,
> I know, but "exclusions" are not documented anyway, only something
> presenting gets documented.

Indeed, such brochures only describe the hardware capability, not so much
its configuration in detail.

> 
> > is limited to this. There are two options here:
> > 
> > 1. make data-lanes mandatory or
> > 
> > 2. add data-lanes as optional with default of four, which the driver
> >     supports and which is known to function.
> 
> If you ask, I'd rather prefer to implement the second option in the dt
> binding documentation and driver, let me know if there are any other
> asked changes to be done in a bulk.

Sounds good.

-- 
Regards,

Sakari Ailus