Re: [PATCH v4 14/29] media: Documentation: Improve LINK_FREQ documentation

Sakari Ailus
2026-04-21T14:42:42Z

Hi Laurent,

On Thu, Apr 16, 2026 at 06:05:03PM +0300, Laurent Pinchart wrote:
> On Wed, Apr 08, 2026 at 06:39:23PM +0300, Sakari Ailus wrote:
> > Add a reference to the LINK_FREQ control and clarify the meaning of the
> > control as for C-PHY the matter is less obvious.
> >
> > Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
> > Reviewed-by: Mirela Rabulea <mirela.rabulea@nxp.com>
> > Reviewed-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>
> > ---
> > Documentation/driver-api/media/tx-rx.rst | 3 ++-
> > .../userspace-api/media/v4l/ext-ctrls-image-process.rst | 4 +++-
> > 2 files changed, 5 insertions(+), 2 deletions(-)
> >
> > diff --git a/Documentation/driver-api/media/tx-rx.rst b/Documentation/driver-api/media/tx-rx.rst
> > index 22e1b13ecde9..7df2407817b3 100644
> > --- a/Documentation/driver-api/media/tx-rx.rst
> > +++ b/Documentation/driver-api/media/tx-rx.rst
> > @@ -93,7 +93,8 @@ where
> > * - variable or constant
> > - description
> > * - link_freq
> > - - The value of the ``V4L2_CID_LINK_FREQ`` integer64 menu item.
> > + - The value of the :ref:`V4L2_CID_LINK_FREQ <v4l2-cid-link-freq>` integer64
> > + menu item.
> > * - nr_of_lanes
> > - Number of data lanes used on the CSI-2 link.
> > * - 2
> > diff --git a/Documentation/userspace-api/media/v4l/ext-ctrls-image-process.rst b/Documentation/userspace-api/media/v4l/ext-ctrls-image-process.rst
> > index 6d516f041ca2..ee88933256dd 100644
> > --- a/Documentation/userspace-api/media/v4l/ext-ctrls-image-process.rst
> > +++ b/Documentation/userspace-api/media/v4l/ext-ctrls-image-process.rst
> > @@ -24,7 +24,9 @@ Image Process Control IDs
> > .. _v4l2-cid-link-freq:
> >
> > ``V4L2_CID_LINK_FREQ (integer menu)``
> > - The frequency of the data bus (e.g. parallel or CSI-2).
> > + The fundamental frequency of the operating symbol rate (serial interfaces
>
> While this is absolutely correct, I think it will confuse most readers
> more than the existing text. Do you think that mentioning that, for
> CSI-2, the frequency is equal to 1 / (2 * UI) would help ?

I'll add that for v5.

>
> > + such as CSI-2) or the sampling rate (parallel interfaces such as DVP or
> > + Bt.565) of the data interface.
> >
> > .. _v4l2-cid-pixel-rate:
> >
>

--
Regards,

Sakari Ailus