On Mon, May 06, 2019 at 03:09:20PM +0200, Thomas Zimmermann wrote:
Hi
Am 06.05.19 um 14:22 schrieb Gerd Hoffmann:
GEM VRAM could implement PRIME helpers, which would allow for using the generic fbcon.
bochs_gem_prime_*() functions with this series applied look like you can just rename them & move over to vram helpers.
It's not a full prime implementation, specifically actual export/import isn't there. But pin+vmap (needed by generic fbcon) is implemented.
I did have a patch to do this, but then I read that prime requires DMA for buffer sharing and bochs works only because it's emulated.
For actual buffer sharing with other drivers yes because dma-bufs typically are a bunch of pages (struct page**) and live in RAM.
Not sure whenever it is possible or useful to place the vram in ZONE_DEVICE to get page structs for it, then export buffers located in vram that way without copying them over to main memory. I suspect most importers would fail to properly setup PCI-PCI dma in that case.
If bochs' implementation is complete enough to be useful for other drivers, I'll add it to the patch set.
It's good enough for generic fbcon.
cheers, Gerd