Re: [PATCH] media: i2c: imx219: Implement .get_frame_desc()

[Sakari Ailus]

Hi Yamike, Mattijs,

On Thu, Aug 13, 2026 at 09:12:03PM +0530, Yemike Abhilash Chandra wrote:
> Hi Mattijs,
> Thanks for the patch.
> 
> On 13/08/26 20:41, Mattijs Korpershoek wrote:
> > From: Vaishnav Achath <vaishnav.a@xxxxxx>
> > 
> > The next subdev in the media graph may want to enquire information such
> > as bus format, virtual channel, bus data type to route the stream from
> > this sensor correctly.
> > 
> > Add support for sharing this information using the .get_frame_desc()
> > callback.
> > 
> > Signed-off-by: Vaishnav Achath <vaishnav.a@xxxxxx>
> > Signed-off-by: Jai Luthra <j-luthra@xxxxxx>
> > Signed-off-by: Yemike Abhilash Chandra <y-abhilashchandra@xxxxxx>
> > Signed-off-by: Mattijs Korpershoek <mkorpershoek@xxxxxxxxxx>
> > ---
> 
> FYI, similar variant of this is already posted by Tomi recently [1].
> 
> On that patch, quoting Sakari [2]:
> 
> "I've been recently working on
> <URL:https://lore.kernel.org/linux-media/20260518164318.3367888-1-sakari.ailus@xxxxxxxxxxxxxxx/>.
> In other words, drivers that have a single stream don't need this. We could
> probably extend that further by making use of the routing information but I
> think that should be left for later."
> 
> I don't really know the status of that series. I will let Sakari to comment.

Good question. I think it'd be nice to have it merged. Laurent's opinion
was the frame descriptors should be part of sub-device state. I don't
really disagree, but moving them there is again an overhaul of that
patchset. If the set isn't merged in the near future, we'll see a large
number of driver specific implementations of both different frame
descriptor functions in sensor drivers as well as receiver drivers
preparing for sensor drivers not supporting get_frame_desc().

The current implementation has issues especially in cases where frame
descriptor has dependencies to upstream frame descriptors. There aren't
many drivers that do that though, but in these cases it has potential for
re-requesting the same frame descriptors rather many times. I wonder if
that's something that could be addressed later though.

-- 
Kind regards,

Sakari Ailus