Re: [PATCH 1/2] of: Add support for linking device tree blobs into vmlinux

[Dirk Brandewie <dirk.brandewie-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

On 11/15/2010 08:41 PM, Grant Likely wrote:
> On Mon, Nov 15, 2010 at 08:01:20PM -0800, dirk.brandewie-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org wrote:
>> From: Dirk Brandewie<dirk.brandewie-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
>>
>> This patch adds support for linking device tree blobs into
>> vmlinux. The device tree blobs are placed in the init.data
>> section.
>>
>> Signed-off-by: Dirk Brandewie<dirk.brandewie-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
>> ---
>>   include/asm-generic/vmlinux.lds.h |   19 +++++++++++++++++--
>>   scripts/Makefile.lib              |   17 +++++++++++++++++
>>   2 files changed, 34 insertions(+), 2 deletions(-)
>>
>> diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
>> index bd69d79..ea671e7 100644
>> --- a/include/asm-generic/vmlinux.lds.h
>> +++ b/include/asm-generic/vmlinux.lds.h
>> @@ -67,7 +67,14 @@
>>    * Align to a 32 byte boundary equal to the
>>    * alignment gcc 4.5 uses for a struct
>>    */
>> -#define STRUCT_ALIGN() . = ALIGN(32)
>> +#define STRUCT_ALIGNMENT 32
>> +#define STRUCT_ALIGN() . = ALIGN(STRUCT_ALIGNMENT)
>> +
>> +/* Device tree blobs linked into the kernel need to have proper
>> + * structure alignment to be parsed by the flat device tree library
>> + * used in early boot
>> +*/
>> +#define DTB_ALIGNMENT STRUCT_ALIGNMENT
>>
>>   /* The actual configuration determine if the init/exit sections
>>    * are handled as text/data or they can be discarded (which
>> @@ -146,6 +153,13 @@
>>   #define TRACE_SYSCALLS()
>>   #endif
>>
>> +
>> +#define KERNEL_DTB()							\
>> +	. = ALIGN(DTB_ALIGNMENT);					\
>> +	VMLINUX_SYMBOL(__dtb_start) = .;				\
>> +	*(.dtb.init.rodata)						\
>> +	VMLINUX_SYMBOL(__dtb_end) = .;
>> +
>>   /* .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()
>>
>>   #define INIT_TEXT							\
>>   	*(.init.text)							\
>> diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
>> index 4c72c11..a8a4774 100644
>> --- a/scripts/Makefile.lib
>> +++ b/scripts/Makefile.lib
>> @@ -200,6 +200,23 @@ quiet_cmd_gzip = GZIP    $@
>>   cmd_gzip = (cat $(filter-out FORCE,$^) | gzip -f -9>  $@) || \
>>   	(rm -f $@ ; false)
>>
>> +# DTC
>> +#  ---------------------------------------------------------------------------
>> +$(obj)/%.dtb.S: $(obj)/%.dtb FORCE
>> +	@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  $(src)/$*.dts
>
> Missing the %.dtb: %.dts rule, but otherwise looks okay.  You will
> need to make sure this doesn't break powerpc or microblaze when the
> dts->dtb rule is added.
>
I have the rule
   $(obj)/%.dtb: $(src)/%.dts
	  $(call if_changed,dtc)
in the arch/x86/kernel/Makefile to prevent this sneaking into other other 
architectures.

I need some more skilled in kbuild to help craft the more generic rule so we can 
have the dts files anywhere in the arch/<*>/ directory structure and be able to 
find the correct dts files.

--Dirk