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

Hi Mattijs, Tomi,

On Fri, Aug 14, 2026 at 11:26:23AM +0200, Mattijs Korpershoek wrote:
> Hi Tomi,
> 
> On Fri, Aug 14, 2026 at 11:21, Tomi Valkeinen <[email protected]> wrote:
> 
> > Hi,
> >
> > On 14/08/2026 11:17, Mattijs Korpershoek wrote:
> >> Hi Sakari,
> >> 
> >> Thank you for the series.
> >> 
> >> On Mon, May 18, 2026 at 19:43, Sakari Ailus <[email protected]> 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?
> > I don't remember the details anymore, but probably related to my comment 
> > in this thread:
> >
> > "It also looks like you only modified platform drivers. Did you check 
> > the i2c drivers? Some call get_frame_desc().". So I think ub953 is 
> > missing the conversion to v4l2_subdev_get_frame_desc().
> 
> Thanks for the hint.
> 
> ub953 and ub960 (which I both use) indirectly call .get_frame_desc() via
> v4l2_subdev_get_frame_desc_passthrough().
> 
> So maybe v4l2_subdev_get_frame_desc_passthrough() needs an update as
> well in this series.

Using v4l2_subdev_call() is still ok as such but it won't be able to return
more routes than it used to.

I've made some changes since which I have pushed to my frame-desc branch in
my linuxtv.org (and FDo) trees but I'm not sure if these address the issue.

-- 
Regards,

Sakari Ailus