Hi Laurent,

On Thu, Feb 08, 2018 at 09:00:19PM +0200, Laurent Pinchart wrote:
> Hi Maxime,
> 
> Thank you for the patch.
> 
> On Wednesday, 7 February 2018 16:26:42 EET Maxime Ripard wrote:
> > The Cadence MIPI-CSI2 TX controller is a CSI2 bridge that supports up to 4
> > video streams and can output on up to 4 CSI-2 lanes, depending on the
> > hardware implementation.
> > 
> > It can operate with an external D-PHY, an internal one or no D-PHY at all
> > in some configurations.
> > 
> > Acked-by: Rob Herring <r...@kernel.org>
> > Signed-off-by: Maxime Ripard <maxime.rip...@bootlin.com>
> > ---
> >  .../devicetree/bindings/media/cdns,csi2tx.txt      | 98 +++++++++++++++++++
> >  1 file changed, 98 insertions(+)
> >  create mode 100644 Documentation/devicetree/bindings/media/cdns,csi2tx.txt
> > 
> > diff --git a/Documentation/devicetree/bindings/media/cdns,csi2tx.txt
> > b/Documentation/devicetree/bindings/media/cdns,csi2tx.txt new file mode
> > 100644
> > index 000000000000..acbbd625a75f
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/media/cdns,csi2tx.txt
> > @@ -0,0 +1,98 @@
> > +Cadence MIPI-CSI2 TX controller
> > +===============================
> > +
> > +The Cadence MIPI-CSI2 TX controller is a CSI-2 bridge supporting up to
> > +4 CSI lanes in output, and up to 4 different pixel streams in input.
> > +
> > +Required properties:
> > +  - compatible: must be set to "cdns,csi2tx"
> > +  - reg: base address and size of the memory mapped region
> > +  - clocks: phandles to the clocks driving the controller
> > +  - clock-names: must contain:
> > +    * esc_clk: escape mode clock
> > +    * p_clk: register bank clock
> > +    * pixel_if[0-3]_clk: pixel stream output clock, one for each stream
> > +                         implemented in hardware, between 0 and 3
> > +
> > +Optional properties
> > +  - phys: phandle to the D-PHY. If it is set, phy-names need to be set
> > +  - phy-names: must contain dphy
> 
> Nitpicking, I'd write "dphy" with double quotes.
> 
> > +Required subnodes:
> > +  - ports: A ports node with one port child node per device input and
> > output
> > +           port, in accordance with the video interface bindings defined in
> > +           Documentation/devicetree/bindings/media/video-interfaces.txt.
> > The
> > +           port nodes numbered as follows.
> 
> s/numbered/are numbered/
> 
> > +
> > +           Port Description
> > +           -----------------------------
> > +           0    CSI-2 output
> > +           1    Stream 0 input
> > +           2    Stream 1 input
> > +           3    Stream 2 input
> > +           4    Stream 3 input
> > +
> > +           The stream input port nodes are optional if they are not
> > +           connected to anything at the hardware level or implemented
> > +           in the design.
> 
> Are they optional (and thus valid if present), or should they be forbidden in 
> case they're not implemented in the hardware ? I'd go for the latter and write
> 
> "One stream input port node is required per implemented hardware input, and 
> no 
> stream input port node can be present for unimplemented inputs."
> 
> > Since there is only one endpoint per port,
> > +           the endpoints are not numbered.
> 
> I think it would be valid to number endpoints even if not required. I think 
> that what you should document is that at most one endpoint is supported per 
> port.

If you allow them to be numbered, then the driver must be able to use any
endpoint number. This provides no additional information on the hardware
while it is more difficult to parse.

That would require reg property in endpoints --- which is not defined here.

I think all new drivers pretty much define it in a similar way (while the
old definitions did not specify it explicitly).

-- 
Kind regards,

Sakari Ailus
e-mail: sakari.ai...@iki.fi

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