Re: [PATCH v2 00/17] Rework frame descriptors

[Mattijs Korpershoek <mkorpershoek@kernel.org>]

Hi Sakari,

Thank you for the series.

On Mon, May 18, 2026 at 19:43, Sakari Ailus <sakari.ailus@linux.intel.com> wrote:

> Hi folks,
>
> This smallish set makes frame descriptors dynamically allocated and
> implements a single-entry frame descriptor based on the device's format,
> using a new helper called v4l2_subdev_get_frame_desc(). All drivers that
> do not obtain their frame descriptor from upstream are converted. The
> helper also obtains a frame descriptor for the desired type (parallel or
> CSI-2) and checks there's at least one entry there. These checks are
> removed from drivers that currently perform them. (Some drivers also check
> there's exactly a single frame descriptor entry but I think in most cases
> this check could be loosened. That could be done after this set.)
>
> On callee side these patches introduce no changes as the number of
> pre-allocated memory for 8 frame descriptors remains as-is. The
> get_frame_desc() pad op can return more than 8 frame descriptors by
> setting the num_entries to the desired number and returning -ENOSPC.
>
> If people prefer using cleanup.h / __free() to release the dynamically
> allocated array (I think I'd almost require that), I'll merge the
> now-separate __v4l2_subdev_get_frame_desc() into
> v4l2_subdev_get_frame_desc().
>
> More formats can be added to df-to-mbus conversion as needed. These are
> meant to be initial formats that are enough for typical raw sensors (and
> one RGB format, too).

I've tried this out on a AM69-SK with the Arducam FPD V3Link[1] using
the following device tree overlays:
  ti/k3-am68-sk-v3link-fusion.dtbo ti/k3-v3link-imx219-0-0.dtbo

See TI's documentation about this [2]

I (naively) assumed that this series would replace Tomi's patch [3], but
it did not. I see the following in dmesg:

[  286.686574] cdns-csi2rx 4504000.csi-bridge: collect_streams: "cdns_csi2rx.4504000.csi-bridge":1: found 0x1 enabled 0x0
[  286.686754] ds90ub953 7-0044: Failed to get frame desc from remote subdev imx219 10-0010
[  286.700147] ds90ub960 7-0030: Failed to get source frame desc for pad 0
[  286.712679] j721e-csi2rx 4500000.ticsi2rx: enable streams "ds90ub960 7-0030":4/0x1
[  286.712684] ds90ub960 7-0030: collect_streams: "ds90ub960 7-0030":4: found 0x1 enabled 0x0
[  286.712690] ds90ub953 7-0044: Failed to get frame desc from remote subdev imx219 10-0010
[  286.725884] j721e-csi2rx 4500000.ticsi2rx: enable streams 4:0x1 failed: -515

Here is my camera topology:
https://paste.debian.net/hidden/7f56f635

I also made the following patch to attempt to convert over j721e-csi2rx:
https://paste.debian.net/hidden/314f9c32

Is this series indeed aimed to replace all sensor-specific
implementations of .get_frame_desc() or are patches such as the one send
from Tomi [3] still useful?

Thanks
Mattijs

[1] https://www.arducam.com/arducam-v3link-camera-kit-for-ti-development-boards.html
[2] https://software-dl.ti.com/jacinto7/esd/processor-sdk-linux-am69/11_00_10_01/exports/docs/linux/Foundational_Components/Kernel/Kernel_Drivers/Camera/CSI2RX.html
[3] https://lore.kernel.org/all/20260611-imx219-frame-desc-v1-1-fe7e975bca6e@ideasonboard.com/

>
> since v1:
>