Hi Tomasz, Helen, Laurent
On 26.05.20 20:57, Laurent Pinchart wrote:
Hi Tomasz,
On Tue, May 26, 2020 at 06:11:00PM +0200, Tomasz Figa wrote:
On Fri, May 22, 2020 at 11:06 AM Helen Koike <helen.koike@xxxxxxxxxxxxx> wrote:
On 5/22/20 4:55 AM, Dafna Hirschfeld wrote:
Hi,
This is v4 of the patchset that was sent by Helen Koike.
Media drivers need to iterate through the pipeline and call .s_stream()
callbacks in the subdevices.
Instead of repeating code, add helpers for this.
These helpers will go walk through the pipeline only visiting entities
that participates in the stream, i.e. it follows links from sink to source
(and not the opposite).
For example, in a topology like this https://bit.ly/3b2MxjI
calling v4l2_pipeline_stream_enable() from rkisp1_mainpath won't call
.s_stream(true) for rkisp1_resizer_selfpath.
stream_count variable was added in v4l2_subdevice to handle nested calls
to the helpers.
This is useful when the driver allows streaming from more then one
capture device sharing subdevices.
If I understand correctly, this isn't true anymore right? Nested calls aren't
possible anymore since this version doesn't contain stream_count in struct v4l2_subdevice.
Documentation of v4l2_pipeline_stream_*() should also be updated.
Just to be clear, without the nested call, vimc will require to add its own
counters, patch https://patchwork.kernel.org/patch/10948833/ will be
required again to allow multi streaming.
Also, patch "media: staging: rkisp1: cap: use v4l2_pipeline_stream_{enable,disable}"
is cleaner in the previous version (with stream_count in struct v4l2_subdevice).
All drivers that allows multi streaming will need to implement some special handling.
Adding stream_count in struct v4l2_subdevice still seems cleaner to me. I'd like to hear
what others think.
I certainly would see this reference counting done in generic code,
because requiring every driver to do it simply adds to the endless
It is required only for drivers that support multistreaming. I don't know much
about other driver except of the ones I am working on, is it a common case?
amount of boiler plate that V4L2 currently requires from the drivers.
:(
I wonder if it wouldn't be possible to redesign the framework so that
.s_stream() at the subdev level is only called when it's expected to
either start or stop this particular subdev and driver's
implementation can simply execute the requested action.
You mean that a generic code similar to the helper functions in this patchset
will be used for all drivers, so that drivers don't call s_stream for subdevices
anymore?
Anyway, this patchset just adds helper functions, it does not redesign the code.
Maybe the stream_count can be updated in the v4l2_subdev_call macro ?
This why it can be used not just for the helper functions.
Thanks,
Dafna
I'd very much like that. Note that I think a few drivers abuse the on
parameter to the function to pass other values than 0 or 1. We'd have to
fix those first (or maybe it has been done already, it's been a long
time since I last checked).
