[libcamera-devel] system locations of libcamera headers

[Umang Jain]

Hi Kieran

On 5/7/21 2:30 PM, Kieran Bingham wrote:
> Hi Umang,
>
> On 07/05/2021 06:24, Umang Jain wrote:
>> Hi all,
>>
>> If I compile the master branch with --prefix=/usr
>> /meson --prefix=/usr -Dpipelines=uvcvideo,ipu3 build && sudo ninja -C
>> build install/
>>
>>
>> The headers turns out to have a directory structure as below:
>>
>>
>> [uajain at localhost libcamera]$ tree /usr/include/libcamera/
>> /usr/include/libcamera/
>> ├── ipa
>> │   ├── ipa_controls.h
>> │   ├── ipa_interface.h
>> │   └── ipa_module_info.h
>> └── libcamera
>>      ├── bound_method.h
>>      ├── buffer.h
>>      ├── camera.h
>>      ├── camera_manager.h
>>      ├── class.h
>>      ├── compiler.h
>>      ├── control_ids.h
>>      ├── controls.h
>>      ├── file_descriptor.h
>>      ├── formats.h
>>      ├── framebuffer_allocator.h
>>      ├── geometry.h
>>      ├── libcamera.h
>>      ├── logging.h
>>      ├── object.h
>>      ├── pixel_format.h
>>      ├── property_ids.h
>>      ├── request.h
>>      ├── signal.h
>>      ├── span.h
>>      ├── stream.h
>>      ├── transform.h
>>      └── version.h
>>
>> 2 directories, 26 files
>>
>>
>> My question is, is this how we want public headers to be placed ? For
>> e.g. the absolute path of signal.h
>> is/usr/include/libcamera/libcamera/signal.h, hence, even the below diff
>> will compile successfully (due to linker find path magic)
>>
>> diff --git a/src/libcamera/object.cpp b/src/libcamera/object.cpp
>> index cd83c684..5f005d1b 100644
>> --- a/src/libcamera/object.cpp
>> +++ b/src/libcamera/object.cpp
>> @@ -9,7 +9,7 @@
>>   
>>   #include <algorithm>
>>   
>> -#include <libcamera/signal.h>
>> +#include <libcamera/libcamera/signal.h>
>
> This gets 'found' because the include path is including "/usr/include/"
> and your include statement specifies the double libcamera, which then
> maps to the full /usr/include/libcamera/libcamera/signal.h path.
>
> However, it's not correct to do so.
>
> The path there is:
>
> /usr/include/<project>/<component>/<header.h>
Ok, this makes it clear - probably we should document <project> vs 
<component> split somewhere?
>
> In this instance, both the project and the component have the same name.
>
>> Considering the case where we also need to expose some of the internal
>> libcamera headers on system locations (for IPAs to use) - It's better to
>> kick off some dicussions around how we would structure the header
>> locations. This will also clear some of my ongoing meson cleanup work
>> (not all patches, but only a couple).
> We already have /usr/include/libcamera/ipa/ for IPA interfaces to be
> installed to.
>
> The issue you are facing is that the IPA interfaces are referencing
> 'internal' and not installed or public headers from
> <sourcetree>/include/libcamera/internal/<private files>
This + internal headers required for the actual IPA

If I take current status quo:
The IPA interface/usr/include/libcamera/ipa/ipa_interface.h needs 
internal header libcamera/internal/camera_sensor.h

And now I were to talk about the actual IPA (out-of-tree one), it would 
require

#include "libcamera/internal/log.h"
#include "libcamera/internal/file.h"
#include "libcamera/internal/buffer.h"
*1
> We need to identify which files are required by the IPA interfaces, and
> find a way (or location) to install them, which makes them available to
> the IPA interface, but makes it clear that they are /not/ a part of the
> public API interfaces, and should not be accessible by applications.
Do you mean the headers(*1)  for actual IPA should be provided via the 
IPA interface, i.e. the IPA interface shall wrap any internal headers 
the /actual/ IPA might require?
>
> Given that they are only to be used by the IPA, we could perhaps install
> a subset of them into libcamera/ipa/internal/ or something like that.
>
> I would like to be able to see a list of what files are required. That
> would help in how we decide what files need abstracting or installing,
> and where they should go.
>
> --
> Kieran
>
>
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