Re: [PATCH v7 3/5] media: Documentation: Update link frequency driver documentation

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On Mon, Dec 16, 2024 at 08:07:26AM +0000, Sakari Ailus wrote:
> Hi Laurent,
> 
> On Sun, Dec 15, 2024 at 07:02:40PM +0200, Laurent Pinchart wrote:
> > On Fri, Dec 13, 2024 at 07:15:55AM +0000, Sakari Ailus wrote:
> > > On Thu, Dec 12, 2024 at 05:53:53PM +0100, Jacopo Mondi wrote:
> > > > On Tue, Dec 10, 2024 at 09:59:04AM +0200, Sakari Ailus wrote:
> > > > > Add the get_mbus_config() as the means for conveying the link frequency
> > > > > towards the receiver drivers.
> > > > >
> > > > > Signed-off-by: Sakari Ailus <sakari.ailus@xxxxxxxxxxxxxxx>
> > > > > ---
> > > > >  Documentation/driver-api/media/tx-rx.rst | 4 ++++
> > > > >  1 file changed, 4 insertions(+)
> > > > >
> > > > > diff --git a/Documentation/driver-api/media/tx-rx.rst b/Documentation/driver-api/media/tx-rx.rst
> > > > > index dd09484df1d3..1430c330fd52 100644
> > > > > --- a/Documentation/driver-api/media/tx-rx.rst
> > > > > +++ b/Documentation/driver-api/media/tx-rx.rst
> > > > > @@ -49,6 +49,10 @@ Link frequency
> > > > >  The :ref:`V4L2_CID_LINK_FREQ <v4l2-cid-link-freq>` control is used to tell the
> > > > >  receiver the frequency of the bus (i.e. it is not the same as the symbol rate).
> > > > >
> > > > > +On devices where the link frequency isn't configurable, the link_freq field of
> > > > > +struct v4l2_mbus_config is recommended over controls for conveying the link
> > > > > +frequency to the downstream driver in the pipeline.
> > > > 
> > > > When read in its entirety, the paragraphs
> > > > 
> > > >  Link frequency
> > > >  ^^^^^^^^^^^^^^
> > > > 
> > > >  The :ref:`V4L2_CID_LINK_FREQ <v4l2-cid-link-freq>` control is used to tell the
> > > >  receiver the frequency of the bus (i.e. it is not the same as the symbol rate).
> > > > 
> > > >  On devices where the link frequency isn't configurable, the link_freq field of
> > > >  struct v4l2_mbus_config is recommended over controls for conveying the link
> > > >  frequency.
> > > > 
> > > > Sounds simpler without the last 7 words.
> > > > 
> > > > A nit and just tastes maybe
> > > 
> > > I used:
> > > 
> > > On devices where the link frequency isn't configurable, using the ``link_freq``
> > > field of struct v4l2_mbus_config is recommended over controls.
> > 
> > Is it a recommendation for the transmitter driver or the receiver driver
> > ? If it's a recommendation for the transmitter driver, does that mean it
> > should not implement V4L2_CID_LINK_FREQ in that case ? How about the
> > need to expose the link frequency to userspace when it's fixed ?
> 
> For the transmitter. Receivers do not implement get_mbus_config op. I can
> add a note on this.

This text is already under "Transmitter drivers".

-- 
Sakari Ailus




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