char: oscar: gasket: add interface to set a separate DMA device

In at least the case of an mfd_cell multi-function device child, the
child platform device does not inherit the DMA / IOMMU configuration
of the parent.  Copying that configuration is non-straightforward or
even likely impossible when the parent device is PCI and holds
pointers to IOMMU-related state only made available for PCI devices.

Add a gasket call to allow platform chip drivers to register their
PCI parent as the device to use for DMA API calls, such that the
chip drivers can workaround this.

Change-Id: I4a4b6de67f5d10197f8ea02d06522090b150d659
Signed-off-by: Todd Poynor <toddpoynor@google.com>
2 files changed