Stefan Kost <ensonic@xxxxxxxxxxxxxxx> writes: Hi, > Arnaud Patard wrote: >> When using VIDIOC_QBUF with memory type set to V4L2_MEMORY_MMAP, the >> v4l2_buffer buffer gets unmodified on drivers like uvc (well, only >> bytesused field is modified). Then some apps like gstreamer are reusing >> the same buffer later to call munmap (eg passing the buffer "length" >> field as 2nd parameter of munmap). >> >> It's working fine on full 32bits but on 32bits systems with 64bit >> kernel, the get_v4l2_buffer32() doesn't copy length/m.offset values and >> then copy garbage to userspace in put_v4l2_buffer32(). >> >> This has for consequence things like that in the libv4l2 logs: >> >> libv4l2: v4l2 unknown munmap 0x2e2b0000, -2145144908 >> libv4l2: v4l2 unknown munmap 0x2e530000, -2145144908 >> >> The buffer are not unmap'ed and then if the application close and open >> again the device, it won't work and logs will show something like: >> >> libv4l2: error setting pixformat: Device or resource busy >> >> The easy solution is to read length and m.offset in get_v4l2_buffer32(). >> >> >> Signed-off-by: Arnaud Patard <apatard@xxxxxxxxxxxx> >> --- >> > I am not sure it even works fine on 32bit. Just yesterday I discovered > https://bugzilla.gnome.org/show_bug.cgi?id=608042 My test app (cheese) is working on the 2 differents 32bits systems I tried and with this patch it's working on my system, so it's possible that your problem is different. Do you get this bug with cheese too ? > > I get this when using gstreamer with my UVC based camera > > request == VIDIOC_STREAMOFF > result == 0 > libv4l2: v4l2 unknown munmap 0xb6d45000, 38400 > libv4l2: v4l2 unknown munmap 0xb6d3b000, 38400 > > I verified that buffer address and size is correct. The libv4l code for > v4l2_munmap could be a bit more verbose in the case of an error ... iirc, libv4l2 is telling you "unknown munmap" is a result of getting a mmap call handled by the driver and not by libv4l2 (the size of your buffer is 38400 and libv4l2 wants/expects the size to be 16777216 to handle it). fwiw, I'm getting "unknown munmap" but that doesn't prevent me to change the resolution in cheese. Arnaud -- 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
