linux-kernel - Re: [PATCH 1/5] of: Add support for linking device tree blobs into vmlinux

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Message-ID: <4CE33C14.9030503@gmail.com>
Date:	Tue, 16 Nov 2010 18:21:08 -0800
From:	Dirk Brandewie <dirk.brandewie@...il.com>
To:	David Daney <ddaney@...iumnetworks.com>
CC:	devicetree-discuss@...ts.ozlabs.org, sodaville@...utronix.de,
	arjan@...ux.intel.com, linuxppc-dev@...ts.ozlabs.org,
	microblaze-uclinux@...e.uq.edu.au, linux-arch@...r.kernel.org,
	linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org,
	dirk.brandewie@...il.com
Subject: Re: [PATCH 1/5] of: Add support for linking device tree blobs into
 vmlinux


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@...il.com wrote:
>> From: Dirk Brandewie<dirk.brandewie@...il.com>
>>
>> /* .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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