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Fix KMS initialization in virtualization environments with separate render/display nodes #2048

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Fix KMS initialization in virtualization environments with separate render/display nodes #2048

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45a4a07
DRMBackend: Return boolean value in init_drm
phreer Dec 23, 2025
573c073
wlrserver: Ensure device opened by wlsession_open_kms is KMS-capable
phreer Dec 23, 2025
958eee9
DRMBackend: Use fallback KMS device if Vulkan primary is unusable
phreer Dec 23, 2025
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15 changes: 8 additions & 7 deletions src/Backends/DRMBackend.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1221,17 +1221,18 @@ bool init_drm(struct drm_t *drm, int width, int height, int refresh)
}

drm->fd = wlsession_open_kms( drm->device_name );
if ( drm->fd < 0 )
if ( drm->fd < 0 && drm->device_name )
{
drm_log.errorf("Could not open KMS device");
return false;
drm_log.infof("retrying with an arbitrary DRM device");
free( drm->device_name );
drm->device_name = nullptr;
drm->fd = wlsession_open_kms( nullptr );
}

if ( !drmIsKMS( drm->fd ) )
if ( drm->fd < 0 )
{
drm_log.errorf( "'%s' is not a KMS device", drm->device_name );
wlsession_close_kms();
return -1;
drm_log.errorf("Could not open KMS device");
return false;
}

if (drmSetClientCap(drm->fd, DRM_CLIENT_CAP_ATOMIC, 1) != 0) {
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6 changes: 6 additions & 0 deletions src/wlserver.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1686,6 +1686,12 @@ int wlsession_open_kms( const char *device_name ) {
wlserver.wlr.device = wlr_session_open_file( wlserver.wlr.session, device_name );
if ( wlserver.wlr.device == nullptr )
return -1;
if ( !drmIsKMS(wlserver.wlr.device->fd) ) {
wl_log.errorf( "'%s' is not a KMS device", device_name );
wlr_session_close_file( wlserver.wlr.session, wlserver.wlr.device );
wlserver.wlr.device = nullptr;
return -1;
}
}
else
{
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