Re: [PATCH 1/5] of: Add support for linking device tree blobs intovmlinux

[Dirk Brandewie]

On 11/16/2010 04:39 PM, David Daney wrote:
> Thanks for doing this. However I have a few comments...
>
> On 11/16/2010 02:41 PM, dirk.brandewie@xxxxxxxxx wrote:
> > From: Dirk Brandewie<dirk.brandewie@xxxxxxxxx>
> >
> > /* .data section */
> > #define DATA_DATA \
> > *(.data) \
> > @@ -468,7 +482,8 @@
> > MCOUNT_REC() \
> > DEV_DISCARD(init.rodata) \
> > CPU_DISCARD(init.rodata) \
> > - MEM_DISCARD(init.rodata)
> > + MEM_DISCARD(init.rodata) \
> > + KERNEL_DTB()
>
> I thought the init.rodata was only for data used by __init things. Although the
> current linker scripts do not put it in the section that gets recycled as usable
> memory.
>
> IIRC the unflattened version of the device tree has pointers to the flattened
> data. Since the device tree nodes are live for the entire kernel lifecycle,
> shouldn't the device tree blobs be in non-init memory?

The contents of the blob get copied to allocated memory during 
unflatten_device_tree() so the blob that is linked in is no longer needed after 
init.

> > #define INIT_TEXT \
> > *(.init.text) \
> > diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
> > index 4c72c11..29db062 100644
> > --- a/scripts/Makefile.lib
> > +++ b/scripts/Makefile.lib
> > @@ -200,6 +200,26 @@ quiet_cmd_gzip = GZIP $@
> > cmd_gzip = (cat $(filter-out FORCE,$^) | gzip -f -9> $@) || \
> > (rm -f $@ ; false)
> >
> > +# DTC
> > +# ---------------------------------------------------------------------------
> > +$(obj)/%.dtb.S: $(obj)/%.dtb FORCE
>
> Why FORCE?
Crud left over from debugging I will remove.
> > + @echo '#include<asm-generic/vmlinux.lds.h>'> $@
> > + @echo '.section .dtb.init.rodata,"a"'>> $@
> > + @echo '.balign DTB_ALIGNMENT'>> $@
> > + @echo '.global __dtb_$(*F)_begin'>> $@
> > + @echo '__dtb_$(*F)_begin:'>> $@
> > + @echo '.incbin "$<" '>> $@
> > + @echo '__dtb_$(*F)_end:'>> $@
> > + @echo '.global __dtb_$(*F)_end'>> $@
> > + @echo '.balign DTB_ALIGNMENT'>> $@
> > +
> > +DTC = $(objtree)/scripts/dtc/dtc
> > +
> > +quiet_cmd_dtc = DTC $@
> > + cmd_dtc = $(DTC) -O dtb -o $(obj)/$*.dtb -b 0 $(DTS_FLAGS) $(src)/dts/$*.dts
> > +
> > +$(obj)/%.dtb: $(src)/dts/%.dts
> > + $(call if_changed,dtc)
>
> Do all the generated files get cleaned up?
>
> I will try it tomorrow to see for sure.
Looks like I need to add the generated .S files to clean-files

> Thanks,
> David Daney

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