[PATCH 1/1] Documentation: media: Document media bus codes to use on serial busses

[PATCH 1/1] Documentation: media: Document media bus codes to use on serial busses

[Sakari Ailus]

Document media bus codes on serial busses. The single sample per pixel
variant is to be chosen from all the possible variants. While this has
been the practice since the introduction of CSI-2 support, it never was
written down. Do it now.

Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
---
 Documentation/driver-api/media/csi2.rst | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/Documentation/driver-api/media/csi2.rst b/Documentation/driver-api/media/csi2.rst
index da8b356389f0..af078ac927bd 100644
--- a/Documentation/driver-api/media/csi2.rst
+++ b/Documentation/driver-api/media/csi2.rst
@@ -10,6 +10,16 @@ the host SoC. It is defined by the `MIPI alliance`_.
 
 .. _`MIPI alliance`: http://www.mipi.org/
 
+Media bus formats
+-----------------
+
+Always use single sample per pixel formats on the CSI-2 bus.
+
+No new media bus formats were created when the support for serial busses were
+added. To avoid using different media bus codes to describe the same format, the
+practice is to use a format that has a single sample per pixel on the parallel
+bus.
+
 Transmitter drivers
 -------------------
 
-- 
2.20.1

Re: [PATCH 1/1] Documentation: media: Document media bus codes to use on serial busses

[Hans Verkuil]

On 19/05/2020 09:21, Sakari Ailus wrote:
> Document media bus codes on serial busses. The single sample per pixel
> variant is to be chosen from all the possible variants. While this has
> been the practice since the introduction of CSI-2 support, it never was
> written down. Do it now.
> 
> Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
> ---
>  Documentation/driver-api/media/csi2.rst | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/Documentation/driver-api/media/csi2.rst b/Documentation/driver-api/media/csi2.rst
> index da8b356389f0..af078ac927bd 100644
> --- a/Documentation/driver-api/media/csi2.rst
> +++ b/Documentation/driver-api/media/csi2.rst
> @@ -10,6 +10,16 @@ the host SoC. It is defined by the `MIPI alliance`_.
>  
>  .. _`MIPI alliance`: http://www.mipi.org/
>  
> +Media bus formats
> +-----------------
> +
> +Always use single sample per pixel formats on the CSI-2 bus.
> +
> +No new media bus formats were created when the support for serial busses were

busses -> buses

(actually, both spellings are used in about equal measures in the kernel, but
the official spelling is 'buses').

were -> was

(the support was added, 'support' is singular)

> +added. To avoid using different media bus codes to describe the same format, the
> +practice is to use a format that has a single sample per pixel on the parallel
> +bus.

To be honest, I'm confused by this text. Probably because I don't know enough
about CSI. I'm not really sure what you mean with 'single sample per pixel'.

Regards,

	Hans

> +
>  Transmitter drivers
>  -------------------
>  
> 

Re: [PATCH 1/1] Documentation: media: Document media bus codes to use on serial busses

[Sakari Ailus]

Hi Hans,

Thanks for the review.

On Tue, May 19, 2020 at 09:56:04AM +0200, Hans Verkuil wrote:
> On 19/05/2020 09:21, Sakari Ailus wrote:
> > Document media bus codes on serial busses. The single sample per pixel
> > variant is to be chosen from all the possible variants. While this has
> > been the practice since the introduction of CSI-2 support, it never was
> > written down. Do it now.
> > 
> > Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
> > ---
> >  Documentation/driver-api/media/csi2.rst | 10 ++++++++++
> >  1 file changed, 10 insertions(+)
> > 
> > diff --git a/Documentation/driver-api/media/csi2.rst b/Documentation/driver-api/media/csi2.rst
> > index da8b356389f0..af078ac927bd 100644
> > --- a/Documentation/driver-api/media/csi2.rst
> > +++ b/Documentation/driver-api/media/csi2.rst
> > @@ -10,6 +10,16 @@ the host SoC. It is defined by the `MIPI alliance`_.
> >  
> >  .. _`MIPI alliance`: http://www.mipi.org/
> >  
> > +Media bus formats
> > +-----------------
> > +
> > +Always use single sample per pixel formats on the CSI-2 bus.
> > +
> > +No new media bus formats were created when the support for serial busses were
> 
> busses -> buses
> 
> (actually, both spellings are used in about equal measures in the kernel, but
> the official spelling is 'buses').

I guess you mean "American"?

> 
> were -> was
> 
> (the support was added, 'support' is singular)

Agreed.

> 
> > +added. To avoid using different media bus codes to describe the same format, the
> > +practice is to use a format that has a single sample per pixel on the parallel
> > +bus.
> 
> To be honest, I'm confused by this text. Probably because I don't know enough
> about CSI. I'm not really sure what you mean with 'single sample per pixel'.

Good catch.

I went to look into mbus format documentation to see how this was expressed
there, only to find the subject is already covered. This need to be
referred to from CSI-2 documentation though.

I'll send v2.

-- 
Regards,

Sakari Ailus