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

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

On 2024-10-22 at 18:05 +02, Jacopo Mondi <jacopo.mondi@ideasonboard.com> wrote:

> Hi Mikhail
>
> On Mon, Oct 21, 2024 at 05:29:33PM +0300, Mikhail Rudenko wrote:
>>
>> 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
>
> set_selection(V4L2_SEL_TGT_COMPOSE) on the internal image pad, stream
> #0
>
>> 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
>
> Existing drivers have adopted creative solutions to allow control of
> the binning factor but all of them are somewhat non-compliant with the
> specs (we went in great lenght in looking at these in the media summit
> 2 years ago). We didn't have internal pads at the time.
>
>> to add binning support to a driver I care about (ov4689), which
>> presently does not implement any binning configuration at all?
>
> Now that you can use internal pads, I would follow what is described
> in patch 3/4 of this series.

Will do so, thanks!

> Thanks
>   j
>
>>
>> --
>> Best regards,
>> Mikhail
>>


--
Best regards,
Mikhail