On Fri, Oct 10, 2014 at 04:09:00PM -0700, Greg Kroah-Hartman wrote:
On Sat, Oct 11, 2014 at 01:37:56AM +0530, Sumit Semwal wrote:
Devices sharing buffers using dma-buf could benefit from sharing their constraints via struct device, and dma-buf framework would manage the common constraints for all attached devices per buffer.
With that information, we could have a 'generic' allocator helper in the form of a central dma-buf exporter, which can create dma-bufs, and allocate backing storage at the time of first call to dma_buf_map_attachment.
This allocation would utilise the constraint-mask by matching it to the right allocator from a pool of allocators, and then allocating buffer backing storage from this allocator.
The pool of allocators could be platform-dependent, allowing for platforms to hide the specifics of these allocators from the devices that access the dma-buf buffers.
A sample sequence could be:
- get handle to cenalloc_device,
- create a dmabuf using cenalloc_buffer_create;
- use this dmabuf to attach each device, which has its constraints set in the constraints mask (dev->dma_params->access_constraints_mask)
- at each dma_buf_attach() call, dma-buf will check to see if the constraint mask for the device requesting attachment is compatible with the constraints of devices already attached to the dma-buf; returns an error if it isn't.
- after all devices have attached, the first call to dma_buf_map_attachment() will allocate the backing storage for the buffer.
- follow the dma-buf api for map / unmap etc usage.
- detach all attachments,
- call cenalloc_buffer_free to free the buffer if refcount reaches zero;
** IMPORTANT** This mechanism of delayed allocation based on constraint-enablement will work *ONLY IF* the first map_attachment() call is made AFTER all attach() calls are done.
Signed-off-by: Sumit Semwal sumit.semwal@linaro.org Cc: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman gregkh@linuxfoundation.org Cc: linux-media@vger.kernel.org Cc: dri-devel@lists.freedesktop.org Cc: linaro-mm-sig@lists.linaro.org
MAINTAINERS | 1 + drivers/cenalloc/cenalloc.c | 597 +++++++++++++++++++++++++++++++++++++++ drivers/cenalloc/cenalloc.h | 99 +++++++ drivers/cenalloc/cenalloc_priv.h | 188 ++++++++++++ 4 files changed, 885 insertions(+) create mode 100644 drivers/cenalloc/cenalloc.c create mode 100644 drivers/cenalloc/cenalloc.h create mode 100644 drivers/cenalloc/cenalloc_priv.h
diff --git a/MAINTAINERS b/MAINTAINERS index 40d4796..e88ac81 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -3039,6 +3039,7 @@ L: linux-media@vger.kernel.org L: dri-devel@lists.freedesktop.org L: linaro-mm-sig@lists.linaro.org F: drivers/dma-buf/ +F: drivers/cenalloc/ F: include/linux/dma-buf* F: include/linux/reservation.h F: include/linux/*fence.h diff --git a/drivers/cenalloc/cenalloc.c b/drivers/cenalloc/cenalloc.c new file mode 100644 index 0000000..f278056 --- /dev/null +++ b/drivers/cenalloc/cenalloc.c @@ -0,0 +1,597 @@ +/*
- Allocator helper framework for constraints-aware dma-buf backing storage
- allocation.
- This allows constraint-sharing devices to deferred-allocate buffers shared
- via dma-buf.
- Copyright(C) 2014 Linaro Limited. All rights reserved.
- Author: Sumit Semwal sumit.semwal@linaro.org
- Structure for management of clients, buffers etc heavily derived from
- Android's ION framework.
Does that mean we can drop ION after this gets merged?
Yeah, I hope so. Not sure whetether this hope is shared by google android people ...
/me dreams
I guess we can collectively dream about this next week at plumbers ;-) I'll try to squeeze in some light review of Sumit's patches between conference travels ...
Cheers, Daniel