mirror of
git://git.kernel.org/pub/scm/linux/kernel/git/xiang/erofs.git
synced 2026-11-14 22:12:14 +01:00
David Brownell
fbf54dd320
This patch updates some of the documentation about DMA buffer management for USB, and ways to avoid extra copying. Our understanding of the issues has improved over time. - Most drivers should *avoid* the dma-coherent allocators. There are a few exceptions (like the HID driver). - Some methods are currently commented out; it seems folk writing USB drivers aren't doing performance tuning at that level yet. - Just avoid highmem; there's no good way to pass an "I can do highmem DMA" capability through a driver stack. This is easy, everything already avoids highmem. But it'd be nice if x86_32 systems with much physical memory could use it directly with network adapters and mass storage devices. (Patch, anyone?) Signed-off-by: David Brownell <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]>