Re: [PATCH virtio] virtio: virtio_console: fix DMA memory allocation for rproc serial

[Christoph Hellwig]

On Tue, Nov 17, 2020 at 03:00:32PM +0100, Arnaud POULIQUEN wrote:
> The dma_declare_coherent_memory allows to associate vdev0buffer memory region
> to the remoteproc virtio device (vdev parent). This region is used to allocated
> the rpmsg buffers.
> The memory for the rpmsg buffer is allocated by the rpmsg_virtio device in
> rpmsg_virtio_bus[1]. The size depends on the total size needed for the rpmsg
> buffers.
> 
> The vrings are allocated directly by the remoteproc device.

Weird.  I thought virtio was pretty strict in not allowing diret DMA
API usage in drivers to support the legacy no-mapping case.

Either way, the point stands:  if you want these magic buffers handed
out to specific rpmsg instances I think not having to detour through the
DMA API is going to make everyones life easier.