Re: [RFC 0/4] Sub-device configuration models

[Mikhail Rudenko <mike.rudenko@gmail.com>]

Hi, Sakari!

On 2024-10-11 at 10:55 +03, Sakari Ailus <sakari.ailus@linux.intel.com> wrote:

> Hello everyone,
>
> I've been recently working (with others) on sub-device streams support as
> well as on internal pads. The two can be used to make sub-device
> configuration more versatile.
>
> At the same time, the added interfaces are much more useful if we require
> specific semantics of those interfaces, so that the user space knows
> exactly what e.g. a given selection target signifies. However, as the same
> selection rectangle could be used for a different purpose on a non-raw
> sensor device, we need a way to tell how should the user space determine
> how to use a given interface.
>
> I'm proposing to solve this problem by introducing sub-device
> configuration models, and by the common raw sensor model, also present in
> this patchset, in particular.
>
> This has been (and will, for some time, continue to be) the reason why I
> have reviewed few sensor driver related patches lately. As we're
> introducing a new interface, it's beneficial to be able to use that
> interface right from the start, rather than trying to later on offer
> compatibility support, which is almost always a fair amount of work with
> less than desirable results in the driver.
>
> With this solved, I believe we can enable the use of the streams UAPI.
>
> Comments are welcome.
>
> The compiled documentation can be found in
> <URL:https://www.retiisi.eu/~sailus/v4l2/tmp/meta-format/output/userspace-api/media/v4l/dev-subdev.html#sub-device-configuration-models>
> and the patches here
> <URL:https://git.linuxtv.org/sailus/media_tree.git/log/?h=metadata>, i.e.
> they're on top of the metadata set.

I've read the updated documentation you shared, and have a question
concerning binning configuration. IIUC binning should be configured via
set_selection(V4L2_SEL_TGT_COMPOSE). But I also see some existing
drivers configure binning via set_fmt() (imx296) or both set_fmt() and
set_selection(V4L2_SEL_TGT_COMPOSE) (imx274). What will be the right way
to add binning support to a driver I care about (ov4689), which
presently does not implement any binning configuration at all?

--
Best regards,
Mikhail