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From: Dafna Hirschfeld <dafna.hirschfeld@collabora.com>
To: Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
	Tomasz Figa <tfiga@chromium.org>
Cc: Helen Koike <helen.koike@collabora.com>,
	Linux Media Mailing List <linux-media@vger.kernel.org>,
	Ezequiel Garcia <ezequiel@collabora.com>,
	Hans Verkuil <hverkuil@xs4all.nl>,
	kernel@collabora.com, Dafna Hirschfeld <dafna3@gmail.com>,
	Sakari Ailus <sakari.ailus@linux.intel.com>,
	"open list:ARM/Rockchip SoC..."
	Mauro Carvalho Chehab <mchehab@kernel.org>,
	Shuah Khan <skhan@linuxfoundation.org>,
Subject: Re: [PATCH v4 0/5] media: add v4l2_pipeline_stream_{enable,disable}
Date: Thu, 28 May 2020 18:21:15 +0200
Message-ID: <50929a55-a071-aa09-eb1a-96776c61c147@collabora.com> (raw)
In-Reply-To: <20200526185754.GA25880@pendragon.ideasonboard.com>

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@collabora.com> 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
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.


> 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).

  reply	other threads:[~2020-05-28 16:21 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-22  7:55 Dafna Hirschfeld
2020-05-22  7:55 ` [PATCH v4 1/5] media: mc-entity.c: add media_graph_walk_next_stream() Dafna Hirschfeld
2020-05-22  7:55 ` [PATCH v4 2/5] media: v4l2-common: add helper functions to call s_stream() callbacks Dafna Hirschfeld
2020-05-25  9:23   ` Sakari Ailus
2020-05-25  9:42     ` Dafna Hirschfeld
2020-05-25 10:03       ` Sakari Ailus
2020-05-25 10:45         ` Dafna Hirschfeld
2020-06-22  9:20           ` Sakari Ailus
2020-06-22  9:00   ` Hans Verkuil
2020-06-22 14:07     ` Dafna Hirschfeld
2020-05-22  7:55 ` [PATCH v4 3/5] media: staging: rkisp1: validate links before powering and streaming Dafna Hirschfeld
2020-06-10 17:00   ` Tomasz Figa
2020-05-22  7:55 ` [PATCH v4 4/5] media: staging: rkisp1: cap: use v4l2_pipeline_stream_{enable,disable} helpers Dafna Hirschfeld
2020-06-10 17:03   ` Tomasz Figa
2020-06-10 17:22     ` Dafna Hirschfeld
2020-06-10 17:28       ` Tomasz Figa
2020-05-22  7:55 ` [PATCH v4 5/5] media: vimc: " Dafna Hirschfeld
2020-05-22  9:06 ` [PATCH v4 0/5] media: add v4l2_pipeline_stream_{enable,disable} Helen Koike
2020-05-26 16:11   ` Tomasz Figa
2020-05-26 18:57     ` Laurent Pinchart
2020-05-28 16:21       ` Dafna Hirschfeld [this message]
2020-05-29 13:26         ` Tomasz Figa
2020-05-29 13:27           ` Tomasz Figa
2020-05-29 13:49             ` Helen Koike
2020-05-29 14:48               ` Tomasz Figa

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