Hi everyone,
I’m in the process of providing a driver for a camera input and have
just finished SG DMA operation to work in hardware and driver. Now I’m
quite surprised that videobuf2-dma-sg is lacking basic support for user
pointers to I/O memory (i.e., to graphics card). However,
videobuf2-dma-contig does have support for it, at least from reading the
code I see that vb2_dc_get_userptr() can tell I/O memory from RAM and as
such do the right thing for I/O. OTOH, vb2_dma_sg_get_userptr() just
does plain get_user_pages() which is not returning any page information
for I/O memory.
Is this missing just because no-one has bothered to do it, or is there a
known problem ? Right now it seems that only one driver in the kernel
tree is actually using videobuf2-dma-sg, so maybe it hasn’t been worth
the effort. Similarly, DMABUF has not been implemented in videobuf2-dma-sg.
Would a patch for adding I/O USERPTR functionality similar to
vb2_dc_get/put_userptr() be accepted? Any known problems with this task
I’m going to face?
Thanks,
– Matthias
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