Hoi, [Please CC me, I'm not subscribed.]
I'm implementing zerocopy transfer from a v4l2 camera to the DSP on an OMAP3 (based on earlier work by Stefan Kost [1][2]). Therefore I'm using V4L2_MEMORY_USERPTR to pass in the memory area allocated by TI's DMAI driver. However, this has flags VM_IO | VM_PFNMAP. This means that it is not possible to do get_user_pages() on it - it's an area that is not pageable and possibly even doesn't pass the MMU. In order to support this kind of zerocopy construct, I propose to add checks for VM_IO | VM_PFNMAP and only get pages from areas that don't have these flags set. I also fixed another issue: it was assumed that dma->sglen == dma->nr_pages, which is not true for the USERPTR memory. Thanks to Sakari Ailus for pointing out a bug I introduced there. Regards, Arnout [1] https://bugzilla.gnome.org/show_bug.cgi?id=583890 [2] http://thread.gmane.org/gmane.linux.drivers.video-input-infrastructure/6209 -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
