Hi Scott, On Thursday 16 June 2011 09:57:05 Scott Jiang wrote: > 2011/6/16 Kassey Lee <kassey1216@xxxxxxxxx>: > > 2011/6/16 Scott Jiang <scott.jiang.linux@xxxxxxxxx>: > >> 2011/6/16 Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>: > >>>> Hi Marek and Laurent, > >>>> > >>>> I am working on v4l2 drivers for blackfin which is a no mmu soc. > >>>> I found videobuf allocate memory in mmap not reqbuf, so I turn to > >>>> videobuf2. But __setup_offsets() use plane offset to fill m.offset, > >>>> which is always 0 for single-planar buffer. > >>>> So pgoff in get_unmapped_area callback equals 0. > >>>> I only found uvc handled get_unmapped_area for no mmu system, but it > >>>> manages buffers itself. > >>>> I really want videobuf2 to manage buffers. Please give me some advice. > >>> > >>> I'm not really sure if I know the differences between mmu and no-mmu > >>> systems (from the device driver perspective). I assume that you are > >>> using videobuf2-vmalloc allocator. Note that memory > >>> allocators/managers are well separated from the videobuf2 logic. If it > >>> the current one doesn't serve you well you can make your own no-mmu > >>> allocator. Later once we identify all differences it might be merged > >>> with the standard one or left alone if the merge is not really > >>> possible or easy. > >> > >> I used dma-contig allocator. I mean if offset is 0, I must get actual > >> addr from this offset. > > > > if it is single plane, surely the offset is 0 for plane 0 > > yes, it is absolutely right. > > > what do you mean the actual addr ? > > I should return virtual address of the buffer in get_unmapped_area > callback. > > >> __find_plane_by_offset can do this. But it is an internal function. > >> I think there should be a function called vb2_get_unmapped_area to do > >> this in framework side. > > > > are you using soc_camera ? > > you can add your get_unmapped_area in soc_camera. > > if not, you can add it in your v4l2_file_operations ops, while still > > using videbuf2 to management your buffer. > > yes, I have added this method, just copy __find_plane_by_offset code. > But it is ugly, it should have a vb2_get_unmapped_area like vb2_mmap. > These two operations are called by one system call, so they should > have a uniform looks. I agree with that. get_unmapped_area is a file operation and should be implemented using a videobuf2 helper, like vb2_mmap. -- Regards, Laurent Pinchart -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
