[libcamera-devel] presentation

[Laurent Pinchart]

Hi Enrique,

On Wed, Apr 29, 2020 at 03:08:44PM +0200, Enrique Artal wrote:
> In the previous reply I forgot to send the output to the list:
> 
> Media controller API version 5.6.7
> 
> Media device information
> ------------------------
> driver          ipu3-cio2
> model           Intel IPU3 CIO2
> serial
> bus info        PCI:0000:00:14.3
> hw revision     0x0
> driver version  5.6.7
> 
> Device topology
> - entity 1: ipu3-csi2 0 (2 pads, 1 link)
>              type V4L2 subdev subtype Unknown flags 0
>              device node name /dev/v4l-subdev0
>      pad0: Sink
>      pad1: Source
>          [fmt:SGRBG10_1X10/1936x1096 field:none]
>          -> "ipu3-cio2 0":0 [ENABLED,IMMUTABLE]
> 
> - entity 4: ipu3-cio2 0 (1 pad, 1 link)
>              type Node subtype V4L flags 0
>              device node name /dev/video0
>      pad0: Sink
>          <- "ipu3-csi2 0":1 [ENABLED,IMMUTABLE]
> 
> - entity 10: ipu3-csi2 1 (2 pads, 1 link)
>               type V4L2 subdev subtype Unknown flags 0
>               device node name /dev/v4l-subdev1
>      pad0: Sink
>      pad1: Source
>          [fmt:SGRBG10_1X10/1936x1096 field:none]
>          -> "ipu3-cio2 1":0 [ENABLED,IMMUTABLE]
> 
> - entity 13: ipu3-cio2 1 (1 pad, 1 link)
>               type Node subtype V4L flags 0
>               device node name /dev/video1
>      pad0: Sink
>          <- "ipu3-csi2 1":1 [ENABLED,IMMUTABLE]
> 
> - entity 19: ipu3-csi2 2 (2 pads, 1 link)
>               type V4L2 subdev subtype Unknown flags 0
>               device node name /dev/v4l-subdev2
>      pad0: Sink
>      pad1: Source
>          [fmt:SGRBG10_1X10/1936x1096 field:none]
>          -> "ipu3-cio2 2":0 [ENABLED,IMMUTABLE]
> 
> - entity 22: ipu3-cio2 2 (1 pad, 1 link)
>               type Node subtype V4L flags 0
>               device node name /dev/video2
>      pad0: Sink
>          <- "ipu3-csi2 2":1 [ENABLED,IMMUTABLE]
> 
> - entity 28: ipu3-csi2 3 (2 pads, 1 link)
>               type V4L2 subdev subtype Unknown flags 0
>               device node name /dev/v4l-subdev3
>      pad0: Sink
>      pad1: Source
>          [fmt:SGRBG10_1X10/1936x1096 field:none]
>          -> "ipu3-cio2 3":0 [ENABLED,IMMUTABLE]
> 
> - entity 31: ipu3-cio2 3 (1 pad, 1 link)
>               type Node subtype V4L flags 0
>               device node name /dev/video3
>      pad0: Sink
>          <- "ipu3-csi2 3":1 [ENABLED,IMMUTABLE]

OK, this is where things get a bit messy I'm afraid. The CIO2 driver
didn't detect the camera sensor. In a nutshell, the driver gets
information about the hardware topology (which sensor is used and how
it's connected) from the platform firmware. On x86, this means ACPI (in
the DSDT table to be exact), on arm it means device tree.

There's no standard to express that information ACPI, and all device
vendors came up with their own solution (there has been some effort to
standardize this though, but no complete formal solution in the ACPI
spec itself). Intel has, for reasons that are out of scope, developed
two different ways to represent that information in the DSDT. One has
been designed for devices manufactured for the Windows market, and
another one for devices manufactured for the Linux market (mostly
Chromebooks). The CIO2 driver only supports the latter, and your device
probably implements the former.

We need to teach the CIO2 driver about the Windows-specific data
representation. The challenge is that, on Windows, vendors usually
hardcode some information in drivers, so not all the information we need
may be available in the DSDT. The information that is available also
makes it difficult to find the sensor from the CIO2, as far as I know
there's no "link" between the two. Finally, the format of the data isn't
documented. Different solutions can be considered, but it will take
someone to do the work. Once that is done, libcamera should be able to
support your device.

All we need is a volunteer :-)

> El 29/4/20 a las 14:22, Laurent Pinchart escribió:
> > On Wed, Apr 29, 2020 at 09:04:57AM +0200, Enrique Artal wrote:
> >> Dear members of the lists,
> >>
> >> I am not a developer, so my contribution to this list may be only for
> >> testing. I use an hp pro x2 612 g2, with Fedora 31 at this time, which
> >> has (I think!) an ipu3 device. I have compiled libcamera and the device
> >> is recognized somehow (four /dev/video*) are created but none of them
> >> are listed with "sudo cam -l"; neither cheese nor webcamoid recognize
> >> them, only ucview seems to detect something with no image. Last git
> >> version is installed. If there is some test that should run for this
> >> device, you can use my assistance. Thanks for you work, Enrique.
> >>
> >> PS. If more data is needed, feel free to ask for it.
> > Could you please send the output of
> >
> > media-ctl -p -d /dev/mediaX
> >
> > for each of the /dev/media* devices present in your system ? media-ctl
> > is part of v4l-utils.

-- 
Regards,

Laurent Pinchart