i.MX GraphicsのトピックRe: DMA Buf import to Vulkan

DMA Buf import to Vulkan

AB22 — Tue, 27 Feb 2024 23:07:33 GMT

I am using an i.MX8M Plus with a MIPI camera. I am writing a compute shader in Vulkan to do video processing. I have a DMA buffer setup which receives the camera frames using V4L2 and the DMA-buf heap protocol. The DMA buffer is in cma-uncached memory. I can memory map this buffer and it appears to be functioning correctly. When I pass the file descriptor to Vulkan, I am unable to get the memory to import. My understanding is that the CPU and GPU share memory so what I am attempting should be possible. Is this correct? Vulkan validation layers do not indicate any problems but the frame data is not imported into my vkBuffer. Any suggestions would be appreciated.

Re: DMA Buf import to Vulkan

Zhiming_Liu — Thu, 29 Feb 2024 02:19:16 GMT

Hi @AB22

I think you may need more debug steps about the data handling process.

1.Make sure the V4L2 driver is working as your want, that frame is stored in memory correctly.

2. I can memory map this buffer and it appears to be functioning correctly

--> Once you check the step1, then check the buffer after mapped.

3.When I pass the file descriptor to Vulkan, I am unable to get the memory to import

-->Firstly, verify dma-buf-import not using VULKAN API. This step is to check if you can dump frame with dma-buf framework.

Best Regards

Zhiming

Re: DMA Buf import to Vulkan

AB22 — Thu, 29 Feb 2024 16:37:45 GMT

Hi @Zhiming_Liu

Thank you for responding. I should elaborate on my testing.

1. We have used the V4L2 driver with this MIPI camera extensively.

2. After using mmap() with reference to the dma-buf file descriptor, I can memcpy and average a portion of the dma-buf and the values change as I adjust the amount of light reaching the camera.

I will attempt to use the user-space dma-buf commands to import the dma-buf without Vulkan as you suggest.

Re: DMA Buf import to Vulkan

AB22 — Thu, 29 Feb 2024 17:38:17 GMT

Hi @Zhiming_Liu

Based on my reading of:

https://docs.kernel.org/driver-api/dma-buf.html

In the section entitled, "CPU Access to DMA Buffer Objects". I believe I am correct in using mmap to look at the dma-buf contents. I don't see another user-space command for this purpose. Is there one I am missing?