This is excellent news, Mike!!! I'd very much like that patch, please! It's been YEARS since I've recompiled a kernel, so this will be a fun trip down memory lane! How long do you think till this patch gets merged into the mainline kernels? Is that even a reasonable aspiration? Asking for a friend 😄 As for the I2C thing, the driver can be blacklisted so that's one workaround. Cheers! On Mon, 2019-10-21 at 20:19 -0500, Mike Isely wrote: > Update... > So the kernel oops is happening because the driver is trying to tear down > state for a V4L2 radio > device - except there was no radio device configured so the tear-down ended > up dereferencing > through a null pointer. Boom. > I backtracked through the code to figure out "why now", and I could not find > a reason. From what > I can tell this bug has likely been there for about 11 years. The code which > bypasses setup of > the radio device takes that path if there's no radio support configured for > the hardware - which > is sadly the case for the HVR-1950 - and git blame shows that area of code > last modified in > 2008. (That makes sense because that's about when the HVR-1950 was added.) > Best I can figure > that some other happenstance had to have prevented the kernel from blowing up > on this > pointer. FWIW, it's actually trying to dereference an offset from null, but > the distance to the > offset is still small enough that it should fit in the first virtual page > address and thus be > detected. > Anyway, I made a change to the two places in the code where this matters, > basically don't touch > the radio data structure if it isn't there, and now the kernel oops is gone. > This also explains why I could not reproduce the problem before - because the > different device I > was trying has a working radio in it that can be operated by the pvrusb2 > driver. Thus this > condition did not arise. > There's still other strangeness to figure out, namely the sysfs teardown > problem and implementing > *something* to keep a userspace I2C client from jamming up the pvrusb2 > driver. But this is > progress. > Obviously I will get this pushed. I can send you a source patch if you'd > like to try rebuilding > the module on your end. Since we're not running identical kernels I can't > just send you the > binary. > -Mike --
Diego Rivera
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