videobuf_iolock function fails for USERPTR?

["Hiremath, Vaibhav" <hvaibhav@xxxxxx>]

Hi,

If I understand correctly, the videobuf_iolock function is responsible for 
mapping user pages to kernel. This works fine as long as user application allocates 
memory/buffer using some standard API (malloc/memalign).

But it fails where; user application has allocated memory/buffer using ioremap 
from another driver. The use case scenario is something -

	- Open V4L2 device (which supports scatter gather DMA)
	- Configure the parameters (especially .memory=V4L2_MEMORY_USERPTR)
	- Request and query the buffer
	- open another device which will be responsible for allocating memory
		Either using ioremap/dma_alloc_coherent/get_free_pages
	- Queue the buffers with buffer address received from previous step

Here it internally calls drv_prepare function, which call videobuf_iolock API for mapping the user pages to kernel and will create scatter-gather (dma->sglist) list. But this API returns from videobuf_dma_init_user_locked with -EFAULT.

I found the get_user_pages returns due to flag VM_IO and VM_PFNMAP for the corresponding vma.

Any suggestions on how can I achieve this?

Thanks,
Vaibhav Hiremath
Senior Software Engg.
Platform Support Products
Texas Instruments Inc
Ph: +91-80-25099927


--
video4linux-list mailing list
Unsubscribe mailto:video4linux-list-request@xxxxxxxxxx?subject=unsubscribe
https://www.redhat.com/mailman/listinfo/video4linux-list