Hi Laurent,

On Sat, 25 Aug 2018, Laurent Pinchart wrote:

Hi Guennadi,

On Friday, 3 August 2018 14:07:12 EEST Guennadi Liakhovetski wrote:

quoted

Hi Laurent,

Thanks for the review. A general note: I think you're requesting a rather
detailed information about many parameters. That isn't a problem by
itself, however, it is difficult to obtain some of that information. I'll
address whatever comments I can in an updated version, just answering some
questions here. I directed youor questions, that I couldn't answer myself
to respective people, but I have no idea if and when I get replies. So,
it's up to you whether to wait for that additional information or to take
at least what we have now.

I've replied to v2, and apart from a few minor points, I think we can apply 
the current version. There are a few small questions I would still like to 
have answers to, but if it takes to long to obtain that, let's not miss v4.20.

quoted

On Sun, 29 Jul 2018, Laurent Pinchart wrote:

quoted

On Saturday, 23 December 2017 13:11:00 EEST Guennadi Liakhovetski wrote:

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From: Guennadi Liakhovetski <redacted>

D4M is a mobile model from the D4XX family of Intel RealSense cameras.
This patch adds a descriptor for it, which enables reading per-frame
metadata from it.

Signed-off-by: Guennadi Liakhovetski <redacted>
---

 Documentation/media/uapi/v4l/pixfmt-meta-d4xx.rst | 202 ++++++++++++++++
 drivers/media/usb/uvc/uvc_driver.c                |  11 ++
 include/uapi/linux/videodev2.h                    |   1 +
 3 files changed, 214 insertions(+)
 create mode 100644 Documentation/media/uapi/v4l/pixfmt-meta-d4xx.rst

diff --git a/Documentation/media/uapi/v4l/pixfmt-meta-d4xx.rst

b/Documentation/media/uapi/v4l/pixfmt-meta-d4xx.rst new file mode 100644
index 0000000..950780d

--- /dev/null
+++ b/Documentation/media/uapi/v4l/pixfmt-meta-d4xx.rst

[snip]

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+    * - :cspan:`1` *Configuration*
+    * - __u32 ID
+      - 0x80000002
+    * - __u32 Size
+      - Size in bytes (currently 40)
+    * - __u32 Version
+      - Version of the struct
+    * - __u32 Flags
+      - A bitmask of flags: see [4_] below
+    * - __u8 Hardware type
+      - Camera hardware version [5_]
+    * - __u8 SKU ID
+      - Camera hardware configuration [6_]
+    * - __u32 Cookie
+      - Internal synchronisation

Internal synchronisation with what ? :-)

This is still something I'd like to understand (and I understand it may still 
take time to receive an answer from the right person).

Sorry, no idea, that flag wasn't even set when I was testing it.

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+    * - __u16 Format
+      - Image format code [7_]
+    * - __u16 Width
+      - Width in pixels
+    * - __u16 Height
+      - Height in pixels
+    * - __u16 Framerate
+      - Requested framerate

What's the unit of this value ?

Is anything other than frames per second used in V4L?

V4L2 expresses the frame rate as a fraction, hence my question, to know 
whether this field contained the number of frames per second as an integer, or 
used a different representation (such as a fixed point decimal value for 
instance).

Nono, sorry, just an integer FPS.

Thanks
Guennadi

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+    * - __u16 Trigger
+      - Byte 0: bit 0:  depth and RGB are synchronised, bit 1: external
trigger
+
+.. _1:
+
+[1]
https://docs.microsoft.com/en-us/windows-hardware/drivers/stream/uvc-ext
ensions-1-5

Should we at some point replicate that documentation in the V4L2 spec ?
Without copying it of course, as that would be a copyright violation.

Well, we don't replicate the UVC itself or any other standards, do we? Of
course, that document doesn't have the same status as an official
vendor-neutral standard, but still, we don't replicate data sheets either.
Besides, I think there are cameras that use this, and windows supports
this, so, don't think it will disappear overnight...

Probably not overnight, you're right. I'm a bit worried about the link 
becoming invalid though. In any case that's not a blocker, but I might at some 
point decide to replicate the documentation.

[snip]

-- 
Regards,

Laurent Pinchart