On Thu 10-04-14 13:07:42, Hans Verkuil wrote: > On 04/10/14 12:32, Jan Kara wrote: > > Hello, > > > > On Thu 10-04-14 12:02:50, Marek Szyprowski wrote: > >> On 2014-03-17 20:49, Jan Kara wrote: > >>> The following patch series is my first stab at abstracting vma handling > >> >from the various media drivers. After this patch set drivers have to know > >>> much less details about vmas, their types, and locking. My motivation for > >>> the series is that I want to change get_user_pages() locking and I want > >>> to handle subtle locking details in as few places as possible. > >>> > >>> The core of the series is the new helper get_vaddr_pfns() which is given a > >>> virtual address and it fills in PFNs into provided array. If PFNs correspond to > >>> normal pages it also grabs references to these pages. The difference from > >>> get_user_pages() is that this function can also deal with pfnmap, mixed, and io > >>> mappings which is what the media drivers need. > >>> > >>> The patches are just compile tested (since I don't have any of the hardware > >>> I'm afraid I won't be able to do any more testing anyway) so please handle > >>> with care. I'm grateful for any comments. > >> > >> Thanks for posting this series! I will check if it works with our > >> hardware soon. This is something I wanted to introduce some time ago to > >> simplify buffer handling in dma-buf, but I had no time to start working. > > Thanks for having a look in the series. > > > >> However I would like to go even further with integration of your pfn > >> vector idea. This structure looks like a best solution for a compact > >> representation of the memory buffer, which should be considered by the > >> hardware as contiguous (either contiguous in physical memory or mapped > >> contiguously into dma address space by the respective iommu). As you > >> already noticed it is widely used by graphics and video drivers. > >> > >> I would also like to add support for pfn vector directly to the > >> dma-mapping subsystem. This can be done quite easily (even with a > >> fallback for architectures which don't provide method for it). I will try > >> to prepare rfc soon. This will finally remove the need for hacks in > >> media/v4l2-core/videobuf2-dma-contig.c > > That would be a worthwhile thing to do. When I was reading the code this > > seemed like something which could be done but I delibrately avoided doing > > more unification than necessary for my purposes as I don't have any > > hardware to test and don't know all the subtleties in the code... BTW, is > > there some way to test the drivers without the physical video HW? > > You can use the vivi driver (drivers/media/platform/vivi) for this. > However, while the vivi driver can import dma buffers it cannot export > them. If you want that, then you have to use this tree: > > http://git.linuxtv.org/cgit.cgi/hverkuil/media_tree.git/log/?h=vb2-part4 Thanks for the pointer that looks good. I've also found drivers/media/platform/mem2mem_testdev.c which seems to do even more testing of the area I made changes to. So now I have to find some userspace tool which can issue proper ioctls to setup and use the buffers and I can start testing what I wrote :) Honza -- Jan Kara <jack@xxxxxxx> SUSE Labs, CR -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>