Function is_dma_available 

pub fn is_dma_available() -> bool

Check if Linux DMA-BUF allocation is available on this system.

Linux-specific availability check (typically requires /dev/dma_heap access — running as root or membership in a video/render group). For portable code that wants “any zero-copy GPU buffer”, use is_gpu_buffer_available which also covers IOSurface on macOS.

This function caches its result after the first call.