Quoting Rodrigo Siqueira (2019-04-18 15:01:49)
> +bool kms_has_vblank(int fd)
> +{
> + drmVBlank dummy_vbl;
> +
> + memset(&dummy_vbl, 0, sizeof(drmVBlank));
> + dummy_vbl.request.type = DRM_VBLANK_RELATIVE;
> +
> + drmWaitVBlank(fd, &dummy_vbl);
> + return (errno != EOPNOTSUPP);
errno is only set on error. It is conceivably that drmWaitVBlank()
suceeed but errno is still set to EOPNOTSUPP from an earlier syscall.
-Chris
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