On 22/04/2022 02:52, Laurent Pinchart wrote:
Hi Tomi,
Thank you for the patch.
On Thu, Apr 21, 2022 at 05:34:47PM +0300, Tomi Valkeinen wrote:
The userspace needs a way to match received metadata buffers to pixel
data buffers. The obvious way to do this is to use the CSI-2 frame
number, as both the metadata and the pixel data have the same frame
number as they come from the same frame.
However, we don't have means to convey the frame number to userspace. We
do have the 'sequence' field, which with a few tricks can be used for
this purpose.
To achieve this, track the frame number for each virtual channel and
increase the sequence for each virtual channel by frame-number -
previous-frame-number, also taking into account the eventual wrap of the
CSI-2 frame number.
This way we get a monotonically increasing sequence number which is
common to all streams using the same virtual channel.
I'd agree in principle, if it wasn't for the fact that sensors are not
required to produce a frame number :-S
In that case the CAL hardware will increment the register every frame.
From CAL doc:
Frame number.
Matches the frame number sent by the camera when the
camera transmits it.
Otherwise, incremented by one on every FS short packet
for this context.
Reset when the context is enabled.
I'll add a note about that to the desc.
Tomi
