There’s
https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/26038. It is
quite appealing to me considering a VK only scenario.
On Thu, Nov 2, 2023 at 5:50 AM Srinivas Pullakavi (QUIC) <
quic_spull...@quicinc.com> wrote:
> Hi Rob,
>
> Thanks for your inputs.
>
> We are planning to use DMA-Buf for GBM backend. DMA-buf supported heaps
> are listed in /dev/dma_heap/
> Gbm backend selects the best heap based on usage. For example: Secure
> buffers will be allocated from secure heap.
>
> Sample output:
> # ls /dev/dma_heap
> reserved system
>
> Sample code to allocate a buffer from system heap:
> int heap_fd = open(/dev/dma_heap/system, O_RDONLY | O_CLOEXEC))
> struct dma_heap_allocation_data heap_data {
> .len = size, // length of data to be
> allocated in bytes
> .fd_flags = O_RDWR | O_CLOEXEC, // permissions for the
> memory to be allocated
> };
> int status = ioctl(heap_fd, DMA_HEAP_IOCTL_ALLOC, &heap_data)
> if (status == 0) {
> int buffer_fd = heap_data.fd;
> }
>
> In this case, there is no dependency on display / Graphics driver. But
> still GBM create device expects a device fd to be passed.
>
> Can we make it optional to pass device fd ?
>
> Thanks,
> Srinivas
>
> -----Original Message-----
> From: Rob Clark <robdcl...@gmail.com>
> Sent: Tuesday, October 24, 2023 1:06 AM
> To: Srinivas Pullakavi (QUIC) <quic_spull...@quicinc.com>
> Cc: mesa-dev@lists.freedesktop.org
> Subject: Re: GBM as standalone buffer allocator
>
> On Mon, Oct 23, 2023 at 6:22 AM Srinivas Pullakavi (QUIC) <
> quic_spull...@quicinc.com> wrote:
> >
> > Hi,
> >
> >
> >
> > We are planning to enhance GBM as a standalone buffer allocator, which
> > can be used for all multi-media clients. Ex: video, camera, display
> > etc;
> >
> >
> >
> > GBM create device expects a file descriptor to be passed, which points
> to drm node. This brings in a dependency on display for buffer allocation.
> On headless devices where display driver is not present, GBM cannot be used
> for buffer allocations. E.g. Recording cases where pipeline is setup
> between Camera, Video, Graphics.
> >
>
> Note that you need some sort of device to allocate buffers from. With
> mesa and upstream kernel, that would be the drm device. (However as Adam
> points out, a drm device does not necessarily need a display..
> for example, several vendors have compute-only GPUs (pci) which have no
> display outputs.)
>
> You might want to look at ChromeOS's minigbm. It already handles these
> cases (buffer sharing across display/gpu/video/camera).
>
> BR,
> -R
>
> [1] https://chromium.googlesource.com/chromiumos/platform/minigbm/
>
> >
> > Could you please share your comments on what will be a good design to
> make GBM flexible for above?
> >
> >
> >
> > Thanks,
> >
> > Srinivas
> >
> >
>
