On 04/10/14 14:15, Jan Kara wrote: > 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 :) Get the v4l-utils.git repository (http://git.linuxtv.org/cgit.cgi/v4l-utils.git/). You want the v4l2-ctl tool. Don't use the version supplied by your distro, that's often too old. 'v4l2-ctl --help-streaming' gives the available options for doing streaming. So simple capturing from vivi is 'v4l2-ctl --stream-mmap' or '--stream-user'. You can't test dmabuf unless you switch to the vb2-part4 branch of my tree. If you need help with testing it's easiest to contact me on the #v4l irc channel. Regards, Hans -- 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
