[RFC PATCH v1] meson: Convert `v4l2` into a feature option

[Barnabás Pőcze]

Hi


2024. december 15., vasárnap 20:52 keltezéssel, Laurent Pinchart <laurent.pinchart at ideasonboard.com> írta:

> Hi Barnabás,
> 
> Thank you for the patch.
> 
> On Sun, Dec 15, 2024 at 07:23:57PM +0000, Barnabás Pőcze wrote:
> > The v4l2 compatibility layer does not have external dependencies,
> > the usual benefits of a feature option do not apply. The main
> > motivation behind this change is making use of the `auto_features`
> > meson option that can change all feature options set to "auto"
> > by default to the desired value.
> >
> > This can be useful for two reasons: (1) using auto_features=disabled
> > and then building up the list of features that are desired in the
> > particular build; (2) using auto_features=enabled to achieve
> > (usually) more testing and compilation coverage.
> 
> The first use case doesn't seem very useful to me, as the v4l2 option is
> set to false by default, so we can already start with the option
> disabled and enable it only when desired.
> 
> The second use case is a bit more interesting.
> 
> You will however need to update CI, and it will break all packaging
> scripts that set the option explicitly to false or true, so I wonder if
> it's really worth it. If there's a general consensus that we should
> change the option type, I'm OK with this patch.

I think it makes sense conceptually to turn this into a feature option.
The transition can be made relatively seamless if that is a concern:

diff --git a/meson_options.txt b/meson_options.txt
index c91cd241a..1f70da0f5 100644
--- a/meson_options.txt
+++ b/meson_options.txt
@@ -84,6 +84,7 @@ option('udev',
        description : 'Enable udev support for hotplug')
 
 option('v4l2',
-        type : 'boolean',
-        value : false,
-        description : 'Compile the V4L2 compatibility layer')
+        type : 'feature',
+        value : 'auto',
+        description : 'Compile the V4L2 compatibility layer',
+        deprecated : {'true': 'enabled', 'false': 'disabled'})


Regards,
Barnabás Pőcze


> 
> > Signed-off-by: Barnabás Pőcze <pobrn at protonmail.com>
> > ---
> >  meson_options.txt    | 4 ++--
> >  src/v4l2/meson.build | 2 +-
> >  2 files changed, 3 insertions(+), 3 deletions(-)
> >
> > diff --git a/meson_options.txt b/meson_options.txt
> > index c91cd241a..08e224561 100644
> > --- a/meson_options.txt
> > +++ b/meson_options.txt
> > @@ -84,6 +84,6 @@ option('udev',
> >         description : 'Enable udev support for hotplug')
> >
> >  option('v4l2',
> > -        type : 'boolean',
> > -        value : false,
> > +        type : 'feature',
> > +        value : 'auto',
> >          description : 'Compile the V4L2 compatibility layer')
> > diff --git a/src/v4l2/meson.build b/src/v4l2/meson.build
> > index 58f53bf3d..e4daf8ae7 100644
> > --- a/src/v4l2/meson.build
> > +++ b/src/v4l2/meson.build
> > @@ -1,6 +1,6 @@
> >  # SPDX-License-Identifier: CC0-1.0
> >
> > -if not get_option('v4l2')
> > +if not get_option('v4l2').allowed()
> >      v4l2_enabled = false
> >      subdir_done()
> >  endif
> 
> --
> Regards,
> 
> Laurent Pinchart
>