From mboxrd@z Thu Jan  1 00:00:00 1970
From: Yann E. MORIN <yann.morin.1998@free.fr>
Date: Thu, 4 Jun 2020 23:23:00 +0200
Subject: [Buildroot] [PATCH v2] package/gstreamer1/gst1-plugins-good:
 Select GUDEV if available
In-Reply-To: <20200601164321.12806-1-ezequiel@vanguardiasur.com.ar>
References: <20200601164321.12806-1-ezequiel@vanguardiasur.com.ar>
Message-ID: <20200604212300.GJ13972@scaer>
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To: buildroot@busybox.net

Ezequiel, Nicolas, All,

On 2020-06-01 13:43 -0300, Ezequiel Garcia spake thusly:
> From: Nicolas Dufresne <nicolas.dufresne@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@collabora.com>
> Signed-off-by: Ezequiel Garcia <ezequiel@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)".

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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