Re: [PATCH v2 0/6] v4l2-subdev: Introduce get_mbus_format pad op

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Hi Laurent,

On Mon, Apr 20, 2020 at 05:02:28AM +0300, Laurent Pinchart wrote:
> Hi Jacopo,
>
> Thank you for the patches.
>
> On Wed, Apr 15, 2020 at 12:49:57PM +0200, Jacopo Mondi wrote:
> > v2 introduces two new patches that could be likely squashed in later to
> > deprecate the g_mbus_config() operation in documentation and expand the newly
> > introduced function documentation by popular demand.
> >
> > Will report again the use cases I'm trying to address here:
> > ------------------------------------------------------------------------------
> > Quoting:
> > https://patchwork.kernel.org/cover/10855919/
> > "The use case this series cover is the following one:
> > the Gen-3 R-Car boards include an ADV748x HDMI/CVBS to CSI-2 converter
> > connected to its CSI-2 receivers. The ADV748x chip has recently gained support
> > for routing both HDMI and analogue video streams through its 4 lanes TXA
> > transmitter, specifically to support the Ebisu board that has a single CSI-2
> > receiver, compared to all other Gen-3 board where the ADV748x TXes are connected
> > to different CSI-2 receivers, and where analogue video is streamed out from the
> > ADV748x single lane TXB transmitter.
> > To properly support transmission of analogue video through TXA, the number of
> > data lanes shall be dynamically reduced to 1, in order to comply with the MIPI
> > CSI-2 minimum clock frequency requirements"
> >
> > During the discussion of the RFC, Dave reported another use case for media
> > bus parameter negotiation on his platform:
> > https://patchwork.kernel.org/patch/10855923/#22569149
> >
> > Another possible use case is for parallel bus multiplexing, where multiple image
> > sensor share the parallel bus lines and they get activated alternatively through
> > an enable signal. While this might not be most clever design, it's often seen
> > in the wild, and this operation allow receivers to re-configure their bus
> > parameter in between streaming session.
>
> Isn't this already supported today, with the bus configuration for each
> source specified in the corresponding endpoint (on the receiver side) in
> DT ?
>

I think you're right.. One should probably cache each endpoint configuration
parsed at probe time.. I was thinking at multiple connections to the
same endpoint, but seems it's not possible.. good, I'll drop this


> > Hyun is now using this series to configure GMSL devices.
> > ------------------------------------------------------------------------------
> >
> > v1->v2:
> > - Address Sakari's comment to use unsigned int in place of bools
> > - Add two new patches to address documentation
> > - Adjust rcar-csi2 patch as much as possible according to Niklas comments
> > - Add Niklas's tags
> >
> > Jacopo Mondi (6):
> >   media: v4l2-subdv: Introduce get_mbus_config pad op
> >   media: v4l2-subdev: Deprecate g_mbus_config video op
> >   media: v4l2-subdev: Expand get_mbus_config doc
> >   media: i2c: adv748x: Adjust TXA data lanes number
> >   media: i2c: adv748x: Implement get_mbus_config
> >   media: rcar-csi2: Negotiate data lanes number
> >
> >  drivers/media/i2c/adv748x/adv748x-core.c    | 31 ++++++--
> >  drivers/media/i2c/adv748x/adv748x-csi2.c    | 15 ++++
> >  drivers/media/i2c/adv748x/adv748x.h         |  1 +
> >  drivers/media/platform/rcar-vin/rcar-csi2.c | 53 ++++++++++++-
> >  include/media/v4l2-subdev.h                 | 82 ++++++++++++++++++++-
> >  5 files changed, 171 insertions(+), 11 deletions(-)
> >
>
> --
> Regards,
>
> Laurent Pinchart



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