Messages in this thread | | | Subject | Re: [PATCH v4 2/8] OF: Introduce DT overlay support. | From | Pantelis Antoniou <> | Date | Mon, 26 May 2014 14:08:32 +0300 |
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Hi Geert,
On May 26, 2014, at 1:57 PM, Geert Uytterhoeven wrote:
> Hi Grant, > > On Mon, May 26, 2014 at 12:48 PM, Grant Likely > <grant.likely@secretlab.ca> wrote: >> On Tue, 20 May 2014 09:38:49 +0200, Geert Uytterhoeven <geert@linux-m68k.org> wrote: >>> On Tue, May 20, 2014 at 7:50 AM, Grant Likely <grant.likely@secretlab.ca> wrote: >>>>> Why has the overlay system been designed for plugging and unpluging whole >>>>> overlays? >>>>> That means the kernel has to remember the full stack, causing issues with >>>>> e.g. kexec. >>>> >>>> Mostly so that drivers don't see any difference in the livetree data >>>> structure. It also means that userspace sees a single representation of >>>> the hardware at any given time. >>> >>> Sorry, I don't follow the argument about the "single representation of the >>> hardware". >> >> Er, s/of the hardware/of the tree/. Right now the overlay design >> modifies the live tree which at the same time modifies the tree >> representation in /sys/firmware/devicetree. If the design was changed to >> keep the overlay logically separate, then I would think we want to >> expose that information to usespace also. In fact, I think we would need >> to for usecases like kexec. > > OK, so it does modify the real tree, and doesn't keep the actual overlays. >
It modifies the actual tree, and it keeps a log of each modification made to the tree so that it will be able to revert the changes made.
> I was under the impression the overlay stack was also kept in memory, to allow > reversal, so there was a misunderstanding. >
Yep.
> Hence for kexec, the tree in /sys/firmware/devicetree can just be passed > to the new kernel, as that's the current representation of the hardware? >
Exactly.
> Gr{oetje,eeting}s, > > Geert >
Regards
-- Pantelis
> -- > Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org > > In personal conversations with technical people, I call myself a hacker. But > when I'm talking to journalists I just say "programmer" or something like that. > -- Linus Torvalds > -- > To unsubscribe from this list: send the line "unsubscribe devicetree" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html
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