[$] DMA-BUF cache handling: Off the DMA API map (part 1) Recently, the
DMA-BUF heaps
interface was added to the 5.6 kernel. This
interface is similar to
ION,
which has been
used for years by Android vendors. However, in trying to move vendors to
use DMA-BUF heaps, we have begun to see how the DMA API model
doesn't fit well for modern mobile devices. Additionally, the lack of clear
guidance in how to handle cache operations efficiently, results in vendors
using custom device-specific optimizations that aren't generic enough for
an upstream solution. This article will describe the nature of the
problem; the upcoming second installment will look at the path toward a
solution.