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

[Kieran Bingham]

Quoting Laurent Pinchart (2024-12-16 11:04:04)
> On Mon, Dec 16, 2024 at 10:59:34AM +0000, Barnabás Pőcze wrote:
> > 2024. december 15., vasárnap 20:52 keltezéssel, Laurent Pinchart írta:
> > > 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'})
> 
> I didn't know about "deprecated", that's interesting. With that,
> 
> Reviewed-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
> 
> and we can drop it after a few releases.

Indeed, I'm fine with that,


Reviewed-by: Kieran Bingham <kieran.bingham at ideasonboard.com>

> 
> > > > 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