On 17/06/2024 09:51, sakari.ailus@xxxxxx wrote:
> Hi Laurent,
>
> On Sat, Jun 15, 2024 at 03:35:25AM +0300, Laurent Pinchart wrote:
>> Hi Neel,
>>
>> On Fri, Jun 14, 2024 at 01:07:24PM +0000, Gandhi, Neel wrote:
>>> Hi Laurent,
>>>
>>> Thank you for your quick response. Please see my below inline response.
>>>
>>> On Friday, June 14, 2024 3:35 PM, Laurent Pinchart wrote:
>>>> On Fri, Jun 14, 2024 at 12:21:20PM +0530, Neel Gandhi wrote:
>>>>> Install mediactl and v4l2subdev header and library files, which may be
>>>>> required by 3rd party applications to populate and control v4l2subdev
>>>>> device node tree
>>>>
>>>> We haven't done so because the API of those libraries is currently internal, and
>>>> not guaranteed to be stable.
>>>
>>> So, if one's application is developed based on those libraries, then
>>> is there any alternative solution for it?
>>
>> Good question. I personally have no issue with applications using those
>> libraries, as long as they don't expect a stable API. This means that
>> any future version of v4l-utils may ship incompatible libraries, and
>> that won't be considered as a regression, and won't be addressed. If we
>> want to go that way, I think we should install static versions of the
>> libraries only, as dynamic linking will really be asking for trouble.
>>
>> A better option, of course, would be to offer a stable API. That will
>> require work, the current API will need to be reviewed and improved to
>> make sure we can then extend it in a backward-compatible way whenever
>> the kernel APIs get extended. It's not work that I could commit to, so
>> we would need a volunteer for work on that and then maintain the
>> libraries.
>>
>> Hans, Sakari, any opinion ?
>
> Given it's been around for a decade without much changes, it wouldn't seem
> unreasonable to consider the API stable. A lot of projects copy the code in
> verbatim which makes fixing bugs very hard. :-(
>
> I think the API could be improved on and the library could use G_TOPOLOGY
> IOCTL. Neither has happened but these don't much affect the value of the
> librarisation.
>
> I've already proposed making this a proper library previously and I still
> believe it should be one.
I quickly looked at the API and I think it needs work before it is suitable
for a generic library API. It is was never meant as a public API.
Making it a proper library is a lot more work and needs someone to maintain
it. I'm not maintaining this code, so it is not up to me, but for what it is
worth, I would recommend against it.
Regards,
Hans
>
>>
>> Neel, out of curiosity, what do you use those libraries for (if you can
>> tell publicly) ?
>>
>>> As in the prior versions of v4l-utils package, those libraries are
>>> available to use but it was removed from v1.25+ onwards (from meson
>>> related changes in c2b91b9c3853b2cbcbe170a542864a3147d179ee commitID).
>>> We're using yocto scarthgap, which is using v1.26.
>>>
>>>>> Signed-off-by: Neel Gandhi <neel.gandhi@xxxxxxx>
>>>>> ---
>>>>> utils/media-ctl/meson.build | 28 +++++++++++++++++++++-------
>>>>> 1 file changed, 21 insertions(+), 7 deletions(-)
>>>>>
>>>>> diff --git a/utils/media-ctl/meson.build b/utils/media-ctl/meson.build
>>>>> index 3a7b0c9a..40669b4c 100644
>>>>> --- a/utils/media-ctl/meson.build
>>>>> +++ b/utils/media-ctl/meson.build
>>>>> @@ -3,14 +3,24 @@ libmediactl_sources = files(
>>>>> 'mediactl-priv.h',
>>>>> )
>>>>>
>>>>> +libmediactl_api = files(
>>>>> + 'mediactl.h',
>>>>> + 'v4l2subdev.h',
>>>>> +)
>>>>> +
>>>>> +install_headers(libmediactl_api, subdir: 'mediactl')
>>>>> +
>>>>> libmediactl_deps = [
>>>>> dep_libudev,
>>>>> ]
>>>>>
>>>>> -libmediactl = static_library('mediactl',
>>>>> - libmediactl_sources,
>>>>> - dependencies : libmediactl_deps,
>>>>> - include_directories : v4l2_utils_incdir)
>>>>> +libmediactl = library('mediactl',
>>>>> + libmediactl_sources,
>>>>> + soversion: '0',
>>>>> + version: '0.0.0',
>>>>> + install : true,
>>>>> + dependencies : libmediactl_deps,
>>>>> + include_directories : v4l2_utils_incdir)
>>>>>
>>>>> dep_libmediactl = declare_dependency(link_with : libmediactl)
>>>>>
>>>>> @@ -18,9 +28,13 @@ libv4l2subdev_sources = files('libv4l2subdev.c')
>>>>> libv4l2subdev_sources += media_bus_format_names_h
>>>>> libv4l2subdev_sources += media_bus_format_codes_h
>>>>>
>>>>> -libv4l2subdev = static_library('v4l2subdev',
>>>>> - libv4l2subdev_sources,
>>>>> - include_directories : v4l2_utils_incdir)
>>>>> +libv4l2subdev = library('v4l2subdev',
>>>>> + libv4l2subdev_sources,
>>>>> + soversion: '0',
>>>>> + version: '0.0.0',
>>>>> + install : true,
>>>>> + dependencies : dep_libmediactl,
>>>>> + include_directories : v4l2_utils_incdir)
>>>>>
>>>>> dep_libv4l2subdev = declare_dependency(link_with : libv4l2subdev)
>>>>>
>>
>
