[PATCH] libcamera: dma_buf_allocator: Work around lack of file seals in uClibc

[Kieran Bingham]

Quoting Laurent Pinchart (2024-06-05 09:35:33)
> uClibc doesn't provide the macros defining parameters for the file
> sealing API. Define them manually as a work around.
> 
> Signed-off-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
> ---
> An alternative would be to disable udmabuf support on such platforms. I
> think we can expect someone running libcamera on a uClibc system to be
> able to enable DMA heaps.

I think this is fine, and keeps our uClibc compile coverage up.

> ---
>  meson.build                         | 4 ++++
>  src/libcamera/dma_buf_allocator.cpp | 5 +++++
>  2 files changed, 9 insertions(+)
> 
> diff --git a/meson.build b/meson.build
> index 1902ea2fd3ff..0ef4cdaafd76 100644
> --- a/meson.build
> +++ b/meson.build
> @@ -74,6 +74,10 @@ cc = meson.get_compiler('c')
>  cxx = meson.get_compiler('cpp')
>  config_h = configuration_data()
>  
> +if cc.has_header_symbol('fcntl.h', 'F_ADD_SEALS', prefix : '#define _GNU_SOURCE')
> +    config_h.set('HAVE_FILE_SEALS', 1)
> +endif
> +
>  if cc.has_header_symbol('unistd.h', 'issetugid')
>      config_h.set('HAVE_ISSETUGID', 1)
>  endif
> diff --git a/src/libcamera/dma_buf_allocator.cpp b/src/libcamera/dma_buf_allocator.cpp
> index d7d08e188a62..1c39441a3415 100644
> --- a/src/libcamera/dma_buf_allocator.cpp
> +++ b/src/libcamera/dma_buf_allocator.cpp
> @@ -157,6 +157,11 @@ UniqueFD DmaBufAllocator::allocFromUDmaBuf(const char *name, std::size_t size)
>                 return {};
>         }
>  
> +#if not HAVE_FILE_SEALS

A one line comment above saying why they are hardcoded here for context
to readers coming across this would be nice but optional.

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

> +#define F_ADD_SEALS    1033
> +#define F_SEAL_SHRINK  0x0002
> +#endif
> +
>         /* udmabuf dma-buffers *must* have the F_SEAL_SHRINK seal. */
>         ret = fcntl(memfd.get(), F_ADD_SEALS, F_SEAL_SHRINK);
>         if (ret < 0) {
> 
> base-commit: 98071d3109c131820439f61d9380c0bd4cd2119a
> -- 
> Regards,
> 
> Laurent Pinchart
>