[PATCH weston] rpi: avoid vc_dispmanx_set_wl_buffer_in_use without EGL

[Kristian Høgsberg]

On Sat, Nov 23, 2013 at 11:30:25AM +0200, Pekka Paalanen wrote:
> 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.

I'll take this to mean that the patch is good to apply.  Done.

Kristian