Re: [PATCH 1/2] dt: bindings: media: Document port and endpoint numbering

[Sakari Ailus]

On Thu, Sep 21, 2017 at 10:58:34AM -0500, Rob Herring wrote:
> On Thu, Sep 21, 2017 at 4:25 AM, Sakari Ailus
>  wrote:
> > Hi Rob,
> >
> > Thanks for the reply.
> >
> > On Wed, Sep 20, 2017 at 03:53:13PM -0500, Rob Herring wrote:
> >> On Mon, Sep 18, 2017 at 11:25:04AM +0300, Sakari Ailus wrote:
> >> > A lot of devices do not need and do not document port or endpoint
> >> > numbering at all, e.g. in case where there's just a single port and a
> >> > single endpoint. Whereas this is just common sense, document it to make 
> >> > it
> >> > explicit.
> >> >
> >> > Signed-off-by: Sakari Ailus 
> >> > ---
> >> >  Documentation/devicetree/bindings/media/video-interfaces.txt | 12 
> >> > 
> >> >  1 file changed, 12 insertions(+)
> >>
> >> This is fine, but bindings should still be explicit. Otherwise, I'm
> >> wondering if it's a single port/endpoint or they just forgot to document
> >> it. And I shouldn't have to look at the example to infer that.
> >>
> >> Acked-by: Rob Herring 
> >
> > The purpose of the patch was to actually document port and endpoint
> > numbering for devices for which it is not documented, not to suggest that
> > this would be omitted in in binding documentation. The fact is that I
> > couldn't find documentation for endpoint numbering for a single device
> > under Documentation/devicetree/bindings/media/ . Yet I haven't come across
> > DT source where other than zero would have been used. And the drivers
> > (mostly?) have ignored endpoint numbers so far.
> 
> That's surprising. I know there are some for display controllers and
> it's a common review comment I give.

On V4L2 side we only have started paying attention recently. See e.g.

Documentation/devicetree/bindings/media/atmel-isc.txt
Documentation/devicetree/bindings/media/ti,omap3isp.txt
Documentation/devicetree/bindings/media/qcom,camss.txt

> 
> >
> > Some bindings have been omitted on the grounds that they're documented in
> > video-interfaces.txt.
> >
> > What would you think of the following? I'm not sure it'd really belong
> > there, but it'd be a small piece of documentation one can easily refer to.
> 
> Looks good.

I'll resend the set, replacing the original patch.

> 
> >
> >
> > From e735979005244eb10597fe5333130b93e41d5a38 Mon Sep 17 00:00:00 2001
> > From: Sakari Ailus 
> > Date: Mon, 18 Sep 2017 11:15:53 +0300
> > Subject: [PATCH 1/1] dt: bindings: media: Document practices for DT 
> > bindings,
> >  ports, endpoints
> >
> > Port and endpoint numbering has been omitted in DT binding documentation
> > for a large number of devices. Also common properties the device uses have
> > been missed in binding documentation. Make it explicit that these things
> > need to be documented.
> >
> > Signed-off-by: Sakari Ailus 
> > ---
> >  .../devicetree/bindings/media/video-interfaces.txt| 15 
> > +++
> >  1 file changed, 15 insertions(+)
> >
> > diff --git a/Documentation/devicetree/bindings/media/video-interfaces.txt 
> > b/Documentation/devicetree/bindings/media/video-interfaces.txt
> > index 852041a..3c5382f 100644
> > --- a/Documentation/devicetree/bindings/media/video-interfaces.txt
> > +++ b/Documentation/devicetree/bindings/media/video-interfaces.txt
> > @@ -55,6 +55,21 @@ divided into two separate ITU-R BT.656 8-bit busses.  In 
> > such case bus-width
> >  and data-shift properties can be used to assign physical data lines to each
> >  endpoint node (logical bus).
> >
> > +Documenting bindings for devices
> > +
> > +
> > +All required and optional bindings the device supports shall be explicitly
> > +documented in device DT binding documentation. This also includes port and
> > +endpoint numbering for the device.
> > +
> > +Port and endpoint numbering
> > +---
> > +
> > +Old binding documentation may have omitted explicitly specifying port and
> > +endpoint numbers. This often applies to devices that have a single port 
> > and a
> > +single endpoint in that port. In this case, the only valid port number for 
> > such
> > +a device is zero. The same applies for devices for which bindings do not
> > +document endpoint numbering: only zero is a valid endpoint.
> >
> >  Required properties
> >  ---
> > --
> > 2.7.4
> >
> > --
> > Sakari Ailus
> > sakari.ai...@linux.intel.com

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

Re: [PATCH 1/2] dt: bindings: media: Document port and endpoint numbering

[Rob Herring]

On Thu, Sep 21, 2017 at 4:25 AM, Sakari Ailus
 wrote:
> Hi Rob,
>
> Thanks for the reply.
>
> On Wed, Sep 20, 2017 at 03:53:13PM -0500, Rob Herring wrote:
>> On Mon, Sep 18, 2017 at 11:25:04AM +0300, Sakari Ailus wrote:
>> > A lot of devices do not need and do not document port or endpoint
>> > numbering at all, e.g. in case where there's just a single port and a
>> > single endpoint. Whereas this is just common sense, document it to make it
>> > explicit.
>> >
>> > Signed-off-by: Sakari Ailus 
>> > ---
>> >  Documentation/devicetree/bindings/media/video-interfaces.txt | 12 
>> > 
>> >  1 file changed, 12 insertions(+)
>>
>> This is fine, but bindings should still be explicit. Otherwise, I'm
>> wondering if it's a single port/endpoint or they just forgot to document
>> it. And I shouldn't have to look at the example to infer that.
>>
>> Acked-by: Rob Herring 
>
> The purpose of the patch was to actually document port and endpoint
> numbering for devices for which it is not documented, not to suggest that
> this would be omitted in in binding documentation. The fact is that I
> couldn't find documentation for endpoint numbering for a single device
> under Documentation/devicetree/bindings/media/ . Yet I haven't come across
> DT source where other than zero would have been used. And the drivers
> (mostly?) have ignored endpoint numbers so far.

That's surprising. I know there are some for display controllers and
it's a common review comment I give.

>
> Some bindings have been omitted on the grounds that they're documented in
> video-interfaces.txt.
>
> What would you think of the following? I'm not sure it'd really belong
> there, but it'd be a small piece of documentation one can easily refer to.

Looks good.

>
>
> From e735979005244eb10597fe5333130b93e41d5a38 Mon Sep 17 00:00:00 2001
> From: Sakari Ailus 
> Date: Mon, 18 Sep 2017 11:15:53 +0300
> Subject: [PATCH 1/1] dt: bindings: media: Document practices for DT bindings,
>  ports, endpoints
>
> Port and endpoint numbering has been omitted in DT binding documentation
> for a large number of devices. Also common properties the device uses have
> been missed in binding documentation. Make it explicit that these things
> need to be documented.
>
> Signed-off-by: Sakari Ailus 
> ---
>  .../devicetree/bindings/media/video-interfaces.txt| 15 
> +++
>  1 file changed, 15 insertions(+)
>
> diff --git a/Documentation/devicetree/bindings/media/video-interfaces.txt 
> b/Documentation/devicetree/bindings/media/video-interfaces.txt
> index 852041a..3c5382f 100644
> --- a/Documentation/devicetree/bindings/media/video-interfaces.txt
> +++ b/Documentation/devicetree/bindings/media/video-interfaces.txt
> @@ -55,6 +55,21 @@ divided into two separate ITU-R BT.656 8-bit busses.  In 
> such case bus-width
>  and data-shift properties can be used to assign physical data lines to each
>  endpoint node (logical bus).
>
> +Documenting bindings for devices
> +
> +
> +All required and optional bindings the device supports shall be explicitly
> +documented in device DT binding documentation. This also includes port and
> +endpoint numbering for the device.
> +
> +Port and endpoint numbering
> +---
> +
> +Old binding documentation may have omitted explicitly specifying port and
> +endpoint numbers. This often applies to devices that have a single port and a
> +single endpoint in that port. In this case, the only valid port number for 
> such
> +a device is zero. The same applies for devices for which bindings do not
> +document endpoint numbering: only zero is a valid endpoint.
>
>  Required properties
>  ---
> --
> 2.7.4
>
> --
> Sakari Ailus
> sakari.ai...@linux.intel.com

Re: [PATCH 1/2] dt: bindings: media: Document port and endpoint numbering

[Sakari Ailus]

Hi Rob,

Thanks for the reply.

On Wed, Sep 20, 2017 at 03:53:13PM -0500, Rob Herring wrote:
> On Mon, Sep 18, 2017 at 11:25:04AM +0300, Sakari Ailus wrote:
> > A lot of devices do not need and do not document port or endpoint
> > numbering at all, e.g. in case where there's just a single port and a
> > single endpoint. Whereas this is just common sense, document it to make it
> > explicit.
> > 
> > Signed-off-by: Sakari Ailus 
> > ---
> >  Documentation/devicetree/bindings/media/video-interfaces.txt | 12 
> > 
> >  1 file changed, 12 insertions(+)
> 
> This is fine, but bindings should still be explicit. Otherwise, I'm 
> wondering if it's a single port/endpoint or they just forgot to document 
> it. And I shouldn't have to look at the example to infer that.
> 
> Acked-by: Rob Herring 

The purpose of the patch was to actually document port and endpoint
numbering for devices for which it is not documented, not to suggest that
this would be omitted in in binding documentation. The fact is that I
couldn't find documentation for endpoint numbering for a single device
under Documentation/devicetree/bindings/media/ . Yet I haven't come across
DT source where other than zero would have been used. And the drivers
(mostly?) have ignored endpoint numbers so far.

Some bindings have been omitted on the grounds that they're documented in
video-interfaces.txt.

What would you think of the following? I'm not sure it'd really belong
there, but it'd be a small piece of documentation one can easily refer to.


>From e735979005244eb10597fe5333130b93e41d5a38 Mon Sep 17 00:00:00 2001
From: Sakari Ailus 
Date: Mon, 18 Sep 2017 11:15:53 +0300
Subject: [PATCH 1/1] dt: bindings: media: Document practices for DT bindings,
 ports, endpoints

Port and endpoint numbering has been omitted in DT binding documentation
for a large number of devices. Also common properties the device uses have
been missed in binding documentation. Make it explicit that these things
need to be documented.

Signed-off-by: Sakari Ailus 
---
 .../devicetree/bindings/media/video-interfaces.txt| 15 +++
 1 file changed, 15 insertions(+)

diff --git a/Documentation/devicetree/bindings/media/video-interfaces.txt 
b/Documentation/devicetree/bindings/media/video-interfaces.txt
index 852041a..3c5382f 100644
--- a/Documentation/devicetree/bindings/media/video-interfaces.txt
+++ b/Documentation/devicetree/bindings/media/video-interfaces.txt
@@ -55,6 +55,21 @@ divided into two separate ITU-R BT.656 8-bit busses.  In 
such case bus-width
 and data-shift properties can be used to assign physical data lines to each
 endpoint node (logical bus).
 
+Documenting bindings for devices
+
+
+All required and optional bindings the device supports shall be explicitly
+documented in device DT binding documentation. This also includes port and
+endpoint numbering for the device.
+
+Port and endpoint numbering
+---
+
+Old binding documentation may have omitted explicitly specifying port and
+endpoint numbers. This often applies to devices that have a single port and a
+single endpoint in that port. In this case, the only valid port number for such
+a device is zero. The same applies for devices for which bindings do not
+document endpoint numbering: only zero is a valid endpoint.
 
 Required properties
 ---
-- 
2.7.4

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

Re: [PATCH 1/2] dt: bindings: media: Document port and endpoint numbering

[Rob Herring]

On Mon, Sep 18, 2017 at 11:25:04AM +0300, Sakari Ailus wrote:
> A lot of devices do not need and do not document port or endpoint
> numbering at all, e.g. in case where there's just a single port and a
> single endpoint. Whereas this is just common sense, document it to make it
> explicit.
> 
> Signed-off-by: Sakari Ailus 
> ---
>  Documentation/devicetree/bindings/media/video-interfaces.txt | 12 
> 
>  1 file changed, 12 insertions(+)

This is fine, but bindings should still be explicit. Otherwise, I'm 
wondering if it's a single port/endpoint or they just forgot to document 
it. And I shouldn't have to look at the example to infer that.

Acked-by: Rob Herring 

[PATCH 1/2] dt: bindings: media: Document port and endpoint numbering

[Sakari Ailus]

A lot of devices do not need and do not document port or endpoint
numbering at all, e.g. in case where there's just a single port and a
single endpoint. Whereas this is just common sense, document it to make it
explicit.

Signed-off-by: Sakari Ailus 
---
 Documentation/devicetree/bindings/media/video-interfaces.txt | 12 
 1 file changed, 12 insertions(+)

diff --git a/Documentation/devicetree/bindings/media/video-interfaces.txt 
b/Documentation/devicetree/bindings/media/video-interfaces.txt
index 852041a..4e0527d 100644
--- a/Documentation/devicetree/bindings/media/video-interfaces.txt
+++ b/Documentation/devicetree/bindings/media/video-interfaces.txt
@@ -55,6 +55,18 @@ divided into two separate ITU-R BT.656 8-bit busses.  In 
such case bus-width
 and data-shift properties can be used to assign physical data lines to each
 endpoint node (logical bus).
 
+Port and endpoint numbering
+---
+
+While the port and endpoint numbers are ultimately specific to a device,
+most devices have more limited scope than what the interface allows. They
+may, for instance, only support a single endpoint on a port. Or there may
+be only a single port on a device.
+
+Therefore, if ports are not explicitly documented for a device, only port
+number zero shall be used. The same applies to endpoints: if endpoint
+numbers are not explicitly documented, only endpoint number zero shall be
+used.
 
 Required properties
 ---
-- 
2.7.4