On 03/25/2014 09:01 AM, Daniel Vetter wrote: > On Tue, Mar 25, 2014 at 4:53 AM, Dave Airlie <airlied@xxxxxxxxx> wrote: >> So I've got a reproducable oops with udl sharing from i915, >> >> start X, connect UDL, randr it into position, rip out udl device, kill X, >> >> we get an oops when dma_unmap_sg in i915_gem_unmap_dma_buf gets >> called, attachment->dev is pointing to a freed structure, now the drm >> + udl driver points dev->dev at the USB interface device, however when >> the device is unplugged, the USB interface device disappears in a poof >> of smoke, and we just keep a fake shell of the drm device around to >> keep userspace happy. >> >> So I'm wondering if should be using a different device to create >> dma-buf objects or whether dma-buf objects need to be keeping a >> reference on the interface device, > Don't do any mapping/attaching then since you never need to do dma > anyway. And I guess if we ever need to do dma with usb devices for > real we just need to teach the usb core about dma-bufs, so that the > *hci can do the attaching and dma-mapping. > > On a quick look through udl_gem.c vmap will keep on working since it's > already forwarded to i915. That leaves mmap - either your userspace > doesn't need this for prime buffers or you'd need to implement that > one too. Rob Clark had patches floating around for forwarding mmaping > through dma-bufs between gem drivers a long time ago, Rob Bradford is > working on dma-buf mmap support for i915. Ouch, here we go! I though the idea was *not* to implement dma-buf mmap() on the major drivers :( ??? /Thomas -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
