On 2/13/19 2:32 PM, Andy Ritger wrote:
On Wed, Feb 13, 2019 at 12:15:02PM -0700, Kyle Brenneman wrote:
On 02/12/2019 01:58 AM, Michel Dänzer wrote:
On 2019-02-11 5:18 p.m., Andy Ritger wrote:
On Mon, Feb 11, 2019 at 12:09:26PM +0100, Michel Dänzer wrote:
On 2019-02-08 11:43 p.m., Kyle Brenneman wrote:
Also, is Mesa the only client-side vendor library that works with the
Xorg GLX module? I vaguely remember that there was at least one other
driver that did, but I don't remember the details anymore.
AFAIK, the amdgpu-pro OpenGL driver can work with the Xorg GLX module
(or its own forked version of it).
Maybe the amdgpu-pro OpenGL driver uses a fork of the Xorg GLX module
(or sets the "GlxVendorLibrary" X configuration option?), but it doesn't
look to me like the in-tree Xorg GLX module could report anything other
than "mesa" for GLX_VENDOR_NAMES_EXT, without custom user configuration.
GLX_VENDOR_NAMES_EXT, which client-side glvnd uses to pick the
libGLX_${vendor}.so to load, is implemented in the Xorg GLX module
with this:
xserver/glx/glxcmds.c:__glXDisp_QueryServerString():
case GLX_VENDOR_NAMES_EXT:
if (pGlxScreen->glvnd) {
ptr = pGlxScreen->glvnd;
break;
}
pGlxScreen->glvnd appears to be assigned here, defaulting to "mesa",
though allowing an xorg.conf override via the "GlxVendorLibrary" option:
xserver/glx/glxdri2.c:__glXDRIscreenProbe():
xf86ProcessOptions(pScrn->scrnIndex, pScrn->options, options);
glvnd = xf86GetOptValString(options, GLXOPT_VENDOR_LIBRARY);
if (glvnd)
screen->base.glvnd = xnfstrdup(glvnd);
free(options);
if (!screen->base.glvnd)
screen->base.glvnd = strdup("mesa");
And swrast unconditionally sets pGlxScreen->glvnd to "mesa":
xserver/glx/glxdriswrast.c:__glXDRIscreenProbe():
screen->base.glvnd = strdup("mesa");
Is there more to this that I'm missing?
I don't think so, I suspect we were just assuming slightly different
definitions of "works". :)
That should get fixed, but since that applies to the libglvnd's normal
vendor selection, I'd say it's orthogonal to GPU offloading. Off the top of
my head, the "GlxVendorLibrary" option ought to work regardless of which
__GLXprovider it finds. I think it would be possible to add a function to
let a driver override the GLX_VENDOR_NAMES_EXT string, too.
I think the point, though, is that thus far, libGLX_mesa.so is the only
glvnd client-side GLX implementation that will be loaded for use with
Xorg's GLX. Thus, it doesn't seem to refute ajax's comment from earlier
in the thread:
I don't see that those are related. The GLX_VENDOR_NAMES_EXT string
tells libglvnd which vendor to use by default. GPU offloading, more or
less by definition, means using something other than the default.
At the other extreme, the server could do nearly all the work of
generating the possible __GLX_VENDOR_LIBRARY_NAME strings (with the
practical downside of each server-side GLX vendor needing to enumerate
the GPUs it can drive, in order to generate the hardware-specific
identifiers).
I don't think this downside is much of a burden? If you're registering
a provider other than Xorg's you're already doing it from the DDX
driver
-Kyle
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