On Saturday, 4 February 2023 02:06:02 CET Dr. David Alan Gilbert wrote: > a) The patch I bisected to is not the root cause of the bug; it just > triggers a ~9 year old bug in the v4l code - so this patch isn't going > to get changed. > > b) The ~9 year old bug is in a particularly hairy piece of memory management > code in v4l that I doubt anyone is going to fix. > > c) The plan is all the drivers using that API are to either be retired > or rewritten using a new API; that's already been done for some of the > drivers and the bttv one is a few months out. I'm not sure that's > any use to this version of Debian though. > > d) The work arounds are: > 1) Disable iommu > 2) some v4l tools can use an mmap interface rather than the read(2) > interface; that seems to be OK. Also reading the upstream conversation, that seems like a good summary :) I could be wrong (ofc), but I doubt this issue will be fixed in kernel 6.1 which is planned to be Bookworm's kernel. What you could do is test any patch(es) they put out and provide feedback on those and if you find that the patch(es) fixes the/your issue, you could consider providing a "Tested-By: yourname <your.email>" which can have a positive effect on the maintainer accepting the patch from which it then can procede further up the chain to Linus. When it does end up in Linus' tree and it would need to have a new Kconfig option enabled in Debian's kernel, feel free to request that. I think IOMMU is a really good thing, so disabling that does not sound ideal, but it could be an acceptable workaround (for now). If you want to run Bookworm on your system, you'd probably have to wait till a suitable Backports kernel becomes available. If you go for Trixie, you should get (in time) the proper fix by just upgrading. Thanks for all the investigative work and bringing it to upstream :-) Cheers, Diederik
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