[Buildroot] [PATCH v2] package/gstreamer1/gst1-plugins-good: Select GUDEV if available

Ezequiel Garcia ezequiel at vanguardiasur.com.ar
Sun Jun 7 20:07:34 UTC 2020


On Thu, 4 Jun 2020 at 18:23, Yann E. MORIN <yann.morin.1998 at free.fr> wrote:
>
> Ezequiel, Nicolas, All,
>
> On 2020-06-01 13:43 -0300, Ezequiel Garcia spake thusly:
> > From: Nicolas Dufresne <nicolas.dufresne at collabora.com>
> >
> > Using udev for probes (such as Video4Linux2 devices probes)
> > and device monitor greatly improves load time and monitoring performance.
> >
> > It also enables hotplug monitoring for cameras.
> >
> > Signed-off-by: Nicolas Dufresne <nicolas.dufresne at collabora.com>
> > Signed-off-by: Ezequiel Garcia <ezequiel at collabora.com>
> > ---
> > v2:
> > * Enable/disable v4l2-gudev explicitly
> >
> >  package/gstreamer1/gst1-plugins-good/Config.in           | 1 +
> >  .../gstreamer1/gst1-plugins-good/gst1-plugins-good.mk    | 9 +++++++++
> >  2 files changed, 10 insertions(+)
> >
> > diff --git a/package/gstreamer1/gst1-plugins-good/Config.in b/package/gstreamer1/gst1-plugins-good/Config.in
> > index 20aebc473e89..be77f5a82e3d 100644
> > --- a/package/gstreamer1/gst1-plugins-good/Config.in
> > +++ b/package/gstreamer1/gst1-plugins-good/Config.in
> > @@ -295,6 +295,7 @@ config BR2_PACKAGE_GST1_PLUGINS_GOOD_PLUGIN_SHOUT2
> >  config BR2_PACKAGE_GST1_PLUGINS_GOOD_PLUGIN_V4L2
> >       bool "v4l2"
> >       depends on BR2_TOOLCHAIN_HEADERS_AT_LEAST_3_0 # multi planar api
> > +     select BR2_PACKAGE_LIBGUDEV if BR2_PACKAGE_HAS_UDEV
>
> So there is still something that evades my understanding: gudev is
> selected only when V4L2 is enabled.
>
> However...
>
> >       help
> >         elements for Video 4 Linux
> >
> > diff --git a/package/gstreamer1/gst1-plugins-good/gst1-plugins-good.mk b/package/gstreamer1/gst1-plugins-good/gst1-plugins-good.mk
> > index 223af9850897..bd4bdcbc1ff1 100644
> > --- a/package/gstreamer1/gst1-plugins-good/gst1-plugins-good.mk
> > +++ b/package/gstreamer1/gst1-plugins-good/gst1-plugins-good.mk
> > @@ -40,6 +40,10 @@ else
> >  GST1_PLUGINS_GOOD_CONF_OPTS += -Djack=disabled
> >  endif
> >
> > +ifeq ($(BR2_PACKAGE_LIBGUDEV),y)
> > +GST1_PLUGINS_GOOD_DEPENDENCIES += libgudev
> > +endif
>
> The dependency is added glbally.
>
> So we end up with this truth table:
>
>       gudev | v4l2 plugin | dependency
>     --------+-------------+------------
>         n   |      n      |     n
>         Y   |      n      |     Y
>         Y   |      Y      |     Y
>
> (the fourth case is not possible, as the v4l2 plugin select gudev)
>
> Is that what you expect?
>
> From the commit log, it looks like v4l2 is only one case amongst many:
> "Using udev for probes (such as Video4Linux2 devices probes)".
>

Yes, that was the idea, but this is a mistake on my side,
as I assumed gudev was being used by other plugins.

Seems Video4Linux2 plugins are really the only gudev users.

The REQUIREMENTS file in gst-plugins-good clarifies this:

Package:        gudev
Version:        >= 147
DebianPackage:  libgudev-1.0-dev
Plugins:        v4l2 (v4l2src)
URL:            http://www.freedesktop.org/software/systemd/
Notes:          This dependency is entirely optional, the video4linux plugin
                will work just fine without it. gudev is only required for
                the device probing and monitoring functionality to detect
                video4linux devices appearing/disappearing at run-time.

Let me get a new patch.

Thanks again for the review,
Ezequiel

> So, I would have expected the select to be on the main
> gst1-plugins0-good symbol:
>
>     menuconfig BR2_PACKAGE_GST1_PLUGINS_GOOD
>         bool "gst1-plugins-good"
>         select BR2_PACKAGE_LIBGUDEV if BR2_PACKAGE_HAS_UDEV
>
> Regards,
> Yann E. MORIN.
>
> >  ifeq ($(BR2_PACKAGE_LIBV4L),y)
> >  GST1_PLUGINS_GOOD_CONF_OPTS += -Dv4l2-libv4l2=enabled
> >  GST1_PLUGINS_GOOD_DEPENDENCIES += libv4l
> > @@ -355,6 +359,11 @@ endif
> >
> >  ifeq ($(BR2_PACKAGE_GST1_PLUGINS_GOOD_PLUGIN_V4L2),y)
> >  GST1_PLUGINS_GOOD_CONF_OPTS += -Dv4l2=enabled
> > +ifeq ($(BR2_PACKAGE_LIBGUDEV),y)
> > +GST1_PLUGINS_GOOD_CONF_OPTS += -Dv4l2-gudev=enabled
> > +else
> > +GST1_PLUGINS_GOOD_CONF_OPTS += -Dv4l2-gudev=disabled
> > +endif
> >  else
> >  GST1_PLUGINS_GOOD_CONF_OPTS += -Dv4l2=disabled
> >  endif
> > --
> > 2.26.0.rc2
> >
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