[PATCH 0/4] drm: Provide a dedicated DMA device for PRIME import

[Thomas Zimmermann]

Importing dma-bufs via PRIME requires a DMA-capable hardware device.
This is not the case for USB, where DMA is controller entirely by the
USB controller instead of the USB devices.

Drivers for USB-based hardware maintainer their own workaround for this
problem. The original ideas to resolve this was to provide different
PRIME helpers for such devices, but the dma-buf code assumes DMA
functionality as well. So that ideas is not realistic.

Let's instead turn the current workaround into a feature. It will also
be useful in other code.

Patch 1 add a dma_device field to struct drm_device and makes the PRIME
code use it. Patches 2 to 4 replace related driver code.

There are other possible users of the new field. The exynos and mediatek
drivers already maintain a dedicated DMA device for non-PRIME code. They
could likely use dma_dev as well. GEM-DMA helpers currently allocate DMA
memory with the regular parent device. They should support the dma_dev
settings as well.

Tested with udl.

Thomas Zimmermann (4):
  drm/prime: Support dedicated DMA device for dma-buf imports
  drm/gm12u320: Set struct drm_device.dma_dev
  drm/gud: Set struct drm_device.dma_dev
  drm/udl: Set struct drm_device.dma_dev

 drivers/gpu/drm/drm_drv.c          |  2 ++
 drivers/gpu/drm/drm_prime.c        |  2 +-
 drivers/gpu/drm/gud/gud_drv.c      | 26 +++----------------
 drivers/gpu/drm/gud/gud_internal.h |  1 -
 drivers/gpu/drm/tiny/gm12u320.c    | 41 ++++++------------------------
 drivers/gpu/drm/udl/udl_drv.c      | 17 -------------
 drivers/gpu/drm/udl/udl_drv.h      |  1 -
 drivers/gpu/drm/udl/udl_main.c     |  9 ++-----
 include/drm/drm_device.h           | 37 +++++++++++++++++++++++++++
 9 files changed, 53 insertions(+), 83 deletions(-)

-- 
2.48.1