[PATCH weston] rpi: avoid vc_dispmanx_set_wl_buffer_in_use without EGL

[Pekka Paalanen]

On Fri, 22 Nov 2013 17:26:58 +0000
Daniel Stone <daniel at fooishbar.org> wrote:

> Hi,
> 
> On 22 November 2013 15:30,  <ppaalanen at gmail.com> wrote:
> > The symbol is needed only for the EGL buffer path. If --disable-egl is
> > given to ./configure, there is no need for it, so fix it to actually not
> > look for that symbol needlessly.
> >
> > This should fix the runtime error:
> >
> >         Failed to load module: .../rpi-backend.so: undefined symbol:
> >         vc_dispmanx_set_wl_buffer_in_use
> >
> > when you use --disable-egl and do not have a recent enough
> > libraspberrypi package (/opt/vc, a.k.a userland.git) that would provide
> > vc_dispmanx_set_wl_buffer_in_use. Apparently no released version of
> > userland yet provides this.
> >
> > The calls are organized into two helper functions to avoid a boolean
> > argument, and put the #ifdefs away from the main parts of the code.
> 
> If you really wanted to gold-plate it, you could call it through dlsym
> instead to avoid the link error altogether, even when someone builds
> with --enable-egl, but doesn't have the support from the vendor
> libraries?

If someone did that, they'd be missing all EGL support anyway, no?

So using --enable-egl would have been in vain in the first place,
we'd just silently not enable it after all. I think that would be
fairly many functions to dlsym, too.

I could do that if you really see use for it, but I don't see it that
useful. Our build guide still has --disable-egl. Making that work
was my goal.

If we had a configure check when --enable-egl on rpi to see
that the function declarations are in the /opt/vc headers, we could
make it complain of an unsupported combination at configure time.


Thanks,
pq