[Mesa-dev] [Bug 38906] Mesa compilation failure if libudev development files are not installed.

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=38906

--- Comment #7 from Kristian Høgsberg <krh at bitplanet.net> 2011-07-02 18:38:02 PDT ---
(In reply to comment #6)
> After doing a bit of readup on this and looking at the commits, I guess you're
> probably right on all accounts,
> 
> but I agree, we should probably rename the platform gdm.
> 
> An embedded device needing something leaner or want to give a device name as an
> environment variable should probably create its own EGL platform code.

I don't think it gets much leaner that gbm.  The gbm code is basically the
driver mapping and loading code we had in the drm platform, refactored into an
actual native EGL platform.  We moved the code around so we load the driver
early (ie before eglGetDisplay), which lets us allocate native buffers for
creating egl surfaces/images, instead of relying on an awkward extension [1].

I don't think udev is a problematic requirement for embedded devices (I think
it's hard to build one without), but one way you could go leaner is to drop the
PCI ID -> driver maps and the libudev dependency, and instead provide a custom
mechanism to map from fd to driver name.  I don't think that conflicts with gbm
though, it could be a configure option if we wanted to do that, but as Benjamin
said, nothing has changed in terms of dependencies or overhead from how the drm
platform worked.

> However, that unfortunate configure option combination should probably be fixed
> so that we see a configure error instead of a compilation error. 

Yes, definitely.

[1] Awkward because it's not in line with how EGLImage was designed.  EGLImage
are always supposed to be created for existing buffers such as textures, render
buffers or native pixmaps.  EGL_MESA_drm_image creates an EGLImage out of
nothing which doesn't work well with the EGLImage specification language.  By
introducing a native platform that just lets us create a native pixmap, we're
more aligned with how EGL platforms are supposed to work and can rely on
EGL_KHR_image_pixmap for creating EGLImages suitable for scanout.

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